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73m1903 modem analog front end simplifying system integration tm data sheet march 20 10 rev. 2.1 ? 2010 teridian semiconductor corporation 1 description the teridian 73m1903 analog front end (afe) ic includes fully differential hybrid driver outputs, which connect to the telephone line interface through a transformer - based daa . the receive pins are also fully differential for maximum flexib ility and performance . this arrangement allows for the design of a high performance hybrid circuit to improve signal to noise performance under low receive level conditions, and compatibility with any standard transformer intended for pstn communications applications. the device incorporates a programmable sample rate circuit to support soft modem and dsp based implementations of all speeds up to v.92 (56 kbps) . the sampling rates supported are from 7.2 khz to 14.4 khz by programming pre - scaler nco and p ll nco. the 73m1903 device incorporates a digital host interface that is compatible with the serial ports found on most commercially available dsps and processors and exchanges both payload and control information with the host . cost - saving features of t he device include an input reference frequency circuit, which accepts a range of crystals from 9 - 27 mhz . it also accepts external reference clock values between 9 - 40 mhz generated by the host processor . in most applications, this eliminates the need for a dedicated crystal oscillator and reduces the bill of material (bom). the 73m1903 also supports two analog loop back and one digital loop back test modes. receive mux/ filters transmit drivers/ filters txap txan (hybrid) daa controls rxap rxan hook analog sigma delta control registers ref. clocks control logic dac vbg serial port sclk sdin sdout fsb crystal gpio features ? up to 56 kbps (v.92) performance ? programmable sample rates (7.2 - 14.4 khz) ? reference clock range of 9 - 40 mhz ? crystal frequency range of 9 - 27 mhz ? host synchronous serial interface operation ? pin compatible with 73m2901cl/ce modems ? low power modes ? on board line interface drivers ? fully differential receiver and transmitter ? drivers for transfo rmer interface ? 3.0 v ? 3.6 v operation ? 5 v tolerant i/o ? industrial temperature range ( - 40 to +85 c) ? jate compliant transmit spectrum ? package options: ? 32- pin qfn ? 20- pin tssop ? rohs compliant (6/6) lead - free package s application s ? set top boxes ? personal v ideo recorders (pvr) ? multifunction peripherals (mfp) ? fax machines ? internet appliances ? game consoles ? point of sale terminals ? automatic teller machines ? speaker phones ? rf modems
73m1903 data sheet ds_1903_032 2 rev. 2 .1 table of contents 1 sign al description ......................................................................................................................... 4 1.1 serial interface ........................................................................................................................ 5 2 control and status registers ........................................................................................................ 8 2.1 gpio .................................................................................................................................... 10 2.1.1 gpio data (gpio): address 02h .............................................................................. 10 2.1.2 gpio direction (dir): address 03h .......................................................................... 10 2.2 analog i/o ............................................................................................................................. 10 2.2.1 control register (ctrl 11): address 0bh ................................................................. 11 2.2.2 control register (ctrl 12): ad dress 0ch ................................................................. 11 2.2.3 control register (ctrl 13): address 0dh ................................................................. 12 2.2.4 control register (ctrl 14): address 0eh ................................................................. 12 3 clock generation ......................................................................................................................... 13 3.1 crystal oscillator and pre - scaler nco ................................................................................... 13 3.1.1 control register ( ctrl 8): address 08h .................................................................... 13 3.1.2 control register (ctrl 9): address 09h .................................................................... 13 3.1.3 control register (ctrl 10): address 0ah ................................................................. 13 4 modem receiver .......................................................................................................................... 18 5 modem transmitter ..................................................................................................................... 21 5.1 transmit levels ..................................................................................................................... 22 5.2 transmit power - dbm ........................................................................................................... 23 5.3 control register (ctrl1): address 00h ............................................................................... 23 5.4 control register (ctrl2): address 01h ............................................................................... 24 5.5 revision register: address 06h ............................................................................................ 24 6 test modes ................................................................................................................................... 25 7 power saving modes ................................................................................................................... 25 8 electrical specifications .............................................................................................................. 26 8.1 absolute maximum ratings ................................................................................................... 26 8.2 recommended operating conditions .................................................................................... 26 8.3 digital specifications ............................................................................................................. 27 8.3.1 dc characteristics ..................................................................................................... 27 8.3.2 ac timing ................................................................................................................. 28 8.4 analog specifications ............................................................................................................ 29 8.4.1 dc specificati ons ...................................................................................................... 29 8.4.2 ac specifications ...................................................................................................... 29 8.5 performance ......................................................................................................................... 30 8.5.1 receiver .................................................................................................................... 30 8.5.2 transmitter ................................................................................................................ 31 9 pinouts ......................................................................................................................................... 33 9.1 32- pin qfn pinout ................................................................................................................ 33 9.2 20- pin tssop pinout ........................................................................................................... 34 10 mechanical specifications .......................................................................................................... 35 10.1 32- pin qfn mecha nical drawings ......................................................................................... 37 10.2 20- pin tssop mechanical drawings .................................................................................... 38 11 ordering information ................................................................................................................... 39 appendix a ? 73m1903 daa resistor calculation guide .................................................................. 40 appendix b ? crystal oscillator .......................................................................................................... 42 revision history .................................................................................................................................. 47
ds_1903_0 32 73m1903 data sheet rev. 2.1 3 figures figure 1: effect of the type (fs mode) pin on fs with sckmode = 0 ....................................................... 7 figure 2: control frame posit ion versus spos ........................................................................................ 7 figure 3: serial port timing diagram ....................................................................................................... 9 figure 4: analog block diagram ............................................................................................................. 11 figure 5: clock generation .................................................................................................................... 17 figure 6: overall receiver frequency response ................................................................................... 19 figure 7: rx passband response .......................................................................................................... 19 figure 8: rxd spectrum of 1 khz tone ................................................................................................. 20 figure 9: rxd spectrum of 0.5 khz, 1 khz, 2 khz, 3 khz and 3.5 khz tones of equal amplitudes ......... 20 figure 10: frequency response of tx path for dc to 4 khz in band signal ........................................... 21 figure 11: serial port data timin g ......................................................................................................... 28 figure 12: 32 - pin qfn pinout ................................................................................................................ 33 figure 13: 20 - pin tssop pin out .......................................................................................................... 34 figure 14: 73m1903 schematic ............................................................................................................. 35 figure 14: 32 - pin qfn mechanical specifications .................................................................................. 37 figure 15: 20 - pin tssop mechanical sp ecifications ............................................................................. 38 figure 16: nco block diagram .............................................................................................................. 42 figure 17: pll block diagram ............................................................................................................... 43 table s table 1: inputs selected in regular and alternate multiplexer cycles ....................................................... 4 table 2: memory map .............................................................................................................................. 8 table 3: pll loop filter settings ........................................................................................................... 11 table 4: kvco versus settings at vc=1.6 v, 25 c .................................................................................. 13 table 5: pll power down ..................................................................................................................... 14 table 6: examples of nco settings ....................................................................................................... 14 table 7: clock generation register settings for fxtal = 27 mhz ............................................................ 15 table 8: clock generation register settings for fxtal = 24.576 mhz ...................................................... 16 table 9: clock generation register settings for fxtal = 9.216 mhz ........................................................ 16 table 10: clock generation register settings for fxtal = 24.000 mhz .................................................... 17 table 11: clock generation register settings for fxtal = 25.35 mhz ...................................................... 17 table 12: receive gain ......................................................................................................................... 18 table 13: peak to rms ratios for various modulation types ................................................................. 23 table 14: serial i/f timing ..................................................................................................................... 28 table 15: reference voltage specifications ........................................................................................... 29 table 16: maximum transmit levels ...................................................................................................... 29 table 17: receiver performance specifications ..................................................................................... 30 table 18: transmitter performance specifications ................................................................................. 31 table 19: 32 - pin qfn pin definitions ..................................................................................................... 33 table 20: 20 - pin tssop pin definitions ................................................................................................ 34 table 21: bill of materials ....................................................................................................................... 36 table 22: ordering information .............................................................................................................. 39
73m1903 data sheet ds_1903_032 4 rev. 2.1 1 sign al description t he teridian 73m1903 modem afe ic is available in a 20 - pin tssop or 32 - p in qfn package with the same pin out . the following table describes the function of each pin. there are two pairs of power supply pins, vpa (analog) and vpd (digital). they should be decoupled separately from the supply source in order to isolate digita l noise from the analog circuits internal to the chip . failure to adequately isolate and decouple these supplies will compromise device performance. table 1 : inputs selected in regular and alternate multiplexer cycles pin name t ype 32qfn p in # 20vt p in # d escription vnd gnd 1,22 2,18 negative digital ground vna gnd 16 13 negative analog ground vpd pwr 2,25 3 positive digital supply vpa pwr 10 8 positive analog supply vppll pwr 20 17 positive pll supply, shared with vpd vnpll p wr 17 14 negative pll ground rst i 9 7 master reset . when this pin is a logic 0 all registers are reset to their default states; weak - pulled high - default . oscin i 19 16 crystal oscillator input . when providing an external clock source, d rive oscin. oscout o 18 15 crystal oscillator circuit output pin. gpio(0 - 7) i/o 3, 4, 5, 6, 23, 24,30,31 n/a software definable digital input/output pins. not available in the 20vt (tssop) package. vref o 13 6 reference voltage pin (reflects vref) . rxap i 15 12 receive analog positive input. rxan i 14 11 receive analog negative input. txap o 12 10 transmit analog positive output. txan o 11 9 transmit analog negative output. sclk o 8 5 serial interface clock. with sclk continuous selected, freque ncy = 256*fs ( =2.4576 mhz for fs=9.6 khz) sdout o 32 1 serial data output (or input to the host). sdin i 29 20 serial data input (or output from the host). fs o 7 4 frame synchronization. (active low) type i 27 19 type of frame sync. open, w eak - pulled high = early (mode1); tied low = late (mode0). sckmode i 28 na controls the sclk behavior after fs . open, weak - pulled high = sclk continuous; tied low = 32 clocks per r/w cycle . not available in 20vt.
ds_1903_0 32 73m1903 data sheet rev. 2.1 5 1.1 serial interface th e serial data port is a bi - directional port that is supported by m any dsps. although the 73m1903 is a peripheral to the dsp (host controller), the 73m1903 is the master of the serial port. it generates a serial bit clock, sclk, from a system clock, syscl k, which is normally an output from an on - chip pll that is programmed by the user . the serial bit clock is derived by dividin g the system clock by 18. the s clk rate, fsclk, is related to the frame synchronization rate, fs, by the relationship fsclk = 256 x fs or fs = fsclk / 256 = fsys / 18 / 256 = fsys / 4608, where fsys is the frequency of sysclk. fs is also the rate at which both the transmit and receive data bytes are sent (received) to (by) the host. throughout this document two pairs of sample ra te s , fs, and crystal frequency, fxtal, will be often cited to facilitate discussions. they are: 1. fxtal 1 = 27 mhz , fs 1 = 7.2 khz 2. fxtal 2 = 18.432 mhz , fs 2 = 8 khz . 3. fxtal 3 = 24.576 mhz , fs 3 = 9.6 khz ? chip default. upon reset, until a switch to the pll b ased clock, pllclk, occurs, the system clock will be at the crystal frequency, fxtal, and therefore the serial bit clock will be s clk = fsys/18 = fxtal/18. examples: 1. if fxtal 1 = 27.000 mhz , then sclk=1.500 mhz and fs=sclk/256 = 5.859375 khz . 2. if fxta l 2 = 18.432 mhz , then sclk=1.024 mhz and fs=sclk /256 = 4.00 khz . 3. if fxtal 3 = 24.576 mhz , then sclk=1.3653 mhz and fs=sclk/256 = 5.33 khz . when 73m1903 is programmed through the serial port to a desired fs and the pll has settled out, the system clock will transition to the pll - based clock in a glitch - le ss manner. examples: 1. if fs 1 = 7.2 khz , fsys = 4608 * fs = 33.1776 mhz and sclk = fsys / 18 = 1.8432 mhz . 2. if fs 2 = 8.0 khz , fsys = 4608 * fs = 36.8640 mhz and sclk = fsys / 18 = 2.048 mhz . 3. if fs 3 = 9.6 khz , fsys = 4608 * fs = 44.2368 mhz and sclk = fsys / 18 = 2.4576 mhz . this transition is entirely controlled by the host . upon reset or power down of pll and/or analog front end, the chip will automatically run off the crystal until the host forces the transition by setting a bit in a designated serial port register ? location bit 7, 0eh. the transition is forced on or after the second frame synch period following the write to a designated pl l programming register (0dh). when reprogramming the pll the host should first transition the system clock to the crystal before reprogramming the pll so that any transients associated with it will not adversely impact the serial port communication. power saving is accomplished by disabling the analog front end by clearing bit 7 of ctrl1 (address 00h), enfe=0 . during the normal operation, a data fs is generated by the 73m 1903 at the rate of fs. for every data fs there are 16 bits transmitted and 16 bits received. the frame synchronization ( fs ) signal is pin prog rammable for type. fs can either be early or late determined by the state of the type input pin. when the type pin is left open, an early fs is generated in the bit clock prior to the first data bit transmitted or received. when held low, a late fs oper ates as a chip select; the fs signal is active for all bits that are transmitted or received. the type input pin is sampled when the reset pin is active (low) and ignored at all other times. the final state of the type pin as the reset pin is de - asserted determines the f rame synchronization mode used.
73m1903 data sheet ds_1903_032 6 rev. 2.1 the bits transmitted on the sdout pin are defined as follows: bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rx15 rx14 rx13 rx12 rx11 rx10 rx9 rx8 rx7 rx6 rx5 rx4 r x3 rx2 rx1 rx0 if the hardware control bit (bit 0 of register 01h) is set to zero, the 16 bits that are received on the sdin are defined as follows: bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 tx15 tx14 tx13 tx12 tx11 tx10 tx9 tx8 tx7 tx6 tx5 tx4 tx3 tx2 tx1 ctl in this case tx0=0 is forced. if the hardware control bit (bit 0 of register 01h) is set to one, the 16 bits that are received on the sdin input are defined as follows: bit15 bit14 bit13 bit12 bit1 1 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 tx15 tx14 tx13 tx12 tx11 tx10 tx9 tx8 tx7 tx6 tx5 tx4 tx3 tx2 tx1 tx0 bit 15 is transmitted/received first . bits rx15:0 are the receive code word. bits tx15:0 are the transmit code word. if th e hardware control bit is set to one, a control frame is initiated between every pair of data frames. if the hardware control bit is set to zero, ctl (tx bit 0) is used by software to request a control frame. if ctl is high, a control frame is initiated before the next data frame. a control frame allows the controller to read or write status and control to the 73m1903. the control word received on the sdin pin is defined as follows: bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 r/w a6 a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 the control word transmitted on the sdout pin is defined as follows: bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 0 0 0 0 0 0 0 0 d7 d6 d5 d4 d3 d2 d1 d0 if the r/w bit is set to a 0, the data byte transmitted on the sdout pin is all zeros and the data received on the sdin pin is written to the register pointed to by the received address bits; a6 - a0. if the r/w bit is set to a 1, there is no wri te to any register and the data byte transmitted on the sdout pin is the data contained in the register pointed to by address bits a6 - a0. only one control frame can occur between any two data frames. writes to unimplemented registers are ignored. readin g an unimplemented register returns a value of 0. the position of a control data frame is controlled by the spos; bit 1 of register 01h. if spos is set to a 0 the control frames occur mid way between data frames, i.e., the time between data frames is eq ual. if spos is set to a 1, the control frame is ? of the way between consecutive data frames, i.e., the control frame is closer to the first data frame. this is illustrated in figure 2 . new to the 73m1903 modem afe ic is a feature that shuts off the se rial clock (sclk) after 32 cycles of sclk following the frame synch ( figure 1 ). this feature is unavailable in the 20 tssop package option . this mode is controlled by the sckmode pin. if this pin is left open, the clock will run continuously. if sckmod e is low the clock will be gated on for 32 clocks for each fs . the sdout and fs pins change values following a rising edge of sclk. the sdin pin is sampled on the falling edge of sclk. figure 4 shows the timing diagrams for the serial port.
ds_1903_0 32 73m1903 data sheet rev. 2.1 7 sclk and fs in mode 1 sclk fs (mode1) 32 cycles of sclk sclk and fs in mode 0 fs (mode0) sclk 32 cycles of sclk figure 1 : effect of the type (fs mode) pin on fs with sckmode = 0 figure 2 : control frame p osition versus spos
73m1903 data sheet ds_1903_032 8 rev. 2.1 2 control and status registers table 2 sh ows the memory map of addressable registers in the 73m1903. each register and its bits are described in detail in the following sections. table 2 : memory map ad d ress default bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 00 08h enfe u nused txbst1 txbst0 txdis rxg1 rxg0 rxgain 01 00h tmen diglb analb intlb r eserved rxpull spos hc 02 ffh gpio7 gpio 6 gpio 5 gpio 4 gpio 3 gpio 2 gpio 1 gpio 0 03 ffh dir7 dir6 dir5 dir4 dir3 dir2 dir1 dir0 04 00h res erved reserved reserved reserved reserved reserved reserved reserved 05 00h reserved reserved reserved reserved reserved reserved reserved reserved 06 10h rev3 rev2 rev1 rev0 u nused r eserved r eserved r eserved 07 00h u nused r eserved r eserved r eserved r es erved r eserved r eserved r eserved 08 00h pseq7 pseq6 pseq5 pseq4 pseq3 pseq2 pseq1 pseq0 09 0ah prst2 prst1 prst0 pdvsr4 pdvsr3 pdvsr2 pdvsr1 pdvsr0 0a 22h ichp3 ichp2 ichp1 ichp0 fl kvco2 kvco1 kvco0 0b 12h u nused ndvsr6 ndvsr5 ndvsr4 ndvsr3 ndvsr2 ndv sr1 ndvsr0 0c 00h nseq7 nseq6 nseq5 nseq4 nseq3 nseq2 nseq1 nseq0 0d c0h xtal1 xtal0 r eserved r eserved u nused nrst2 nrst1 nrst0 0e 00h frcvco pwdnpll r eserved u nused u nused u nused u nused u nused 0f - 7f u nused u nused u nused u nused u nused u nused u nused u n used to prevent unintended operation, do not write to reserved or unused locations. these locations are for factory test or future use only and are not intended for customer programming.
ds_1903_032 73m1903 data sheet rev. 2.1 9 fs (mode1) tx15 tx12 tx11 tx10 tx9 tx13 tx8 tx7 tx6 tx5 tx4 tx3 tx2 tx1 ctl tx14 rx15 rx12 rx11 rx10 rx9 rx13 rx8 rx7 rx6 rx5 rx4 rx3 rx2 rx1 rx0 rx14 data frame with early frame sync sclk sdin sdout r/w a4 a3 a2 a1 a5 a0 di7 di6 di5 di4 di3 di2 di1 di0 a6 zero zero zero zero zero zero zero do7 do6 do5 do4 do3 do2 do1 do0 zero control frame with early frame sync sclk sdin sdout fs (mode1) r/w a4 a3 a2 a1 a5 a0 di7 di6 di5 di4 di3 di2 di1 di0 a6 zero zero zero zero zero zero zero do7 do6 do5 do4 do3 do2 do1 do0 zero control frame with late frame sync sclk sdin sdout fs (mode0) sclk fs sdin sdout tx tx tx tx tx 1 rx rx rx rx rx rx r a a di di di 0 0 0 do do do a 0 tx tx tx tx tx 0 rx rx rx rx rx rx 7.2khz (8khz) data frame control frame data frame relation between the data and control frames figure 3 : serial port tim i ng diagram
73m1903 data sheet ds_1903_032 10 rev. 2.1 2.1 gpio the 73m1903 modem afe device provides 8 user defined i/o pins . each pin is programmed separately as either an input or an output by a bit in a direction register . if the bit in the direction register is set high, the corresponding pin is an input whose value is read from the gpio data register . if it is low, the pin will be treated as an output whose value is set by the gpio data register. to avoid unwanted current contention and consumption in the system from the gpio port before the g pio is configured after a reset, the gpio port i/os are initialized to a high impedance state . the input structures are protected from floating inputs, and no output levels are driven by any of the gpio pins . the gpio pins are configured as inputs or ou tputs when the host controller (or dsp) writes to the gpio direction register. the gpio direction and data registers are initialized to all ones (ffh) upon reset . 2.1.1 gpio data (gpio): address 02h reset state ffh bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 b it 0 gpio7 gpio6 gpio5 gpio4 gpio3 gpio2 gpio1 gpio0 bits in this register will be asserted on the gpio(7:0) pins if the corresponding direction register bit is a 0. reading this address will return data reflectin g the values of pins gpio(7:0). 2.1.2 gpio di rection (dir): address 03h reset state ffh bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 dir7 dir6 dir5 dir4 dir3 dir2 dir1 dir0 this register is used to designate the gpio pins as either inputs or outputs . if the register bit is low, the correspon ding gpio pin is programmed as an output . if the register bit is a 1, the corresponding p in will be treated as an input. 2.2 analog i/o figure 4 shows the block diagram of the analog front end. the analog interface circuit uses differential transmit and receive signals to and from the external circuitry. t he hybrid driver in the 73m1903 ic is capable of connecting directly, but not limited to, a transformer - based direct access arrangement (daa). the hybrid driver i s capable of driving the daa?s line coupling transformer, which carries an impedance on the primary side that is typically rated at 600 , depending on the transformer and matching network . the hybrid drivers can also drive high impedance loads without modification . the class ab behavior of the amplifiers provides lo ad dependent power consumption. an on - chip band gap voltage is used to provide an internal voltage reference and bias currents for the analog receive and transmit channels. the reference derived from the bandgap, nominally 1.25 volts, is multiplied to 1.36 volts and output at the vref pin. several voltage references, nomina lly 1.25 volts, are used in the analog circuits. the band gap and reference circuits are disabled after a chip reset since the enfe bit is reset to a default state of zero. when enfe=0, the band gap voltage and the analog bias currents are disabled. in this case all of the analog circuits are powered down and draw less than 5 a of current. a clock generator (ckgn) is used to create all of the non - overlapping phase clocks needed for the time sampled switched - capacitor circuits, asdm, dac1 , and tlpf. th e ckgn input is two times the analog/digital interface sample rate or 3.072 mhz clock for fs=8 khz .
ds_1903_032 73m1903 data sheet rev. 2.1 11 figure 4 : analog block d iagram table 3 : pll loop filter settings fl pllloop filter s ettings 0 r1=32 k, c1=100 pf,c2=2.5 pf 1 r1=16 k, c1=100 pf,c2=2.5 pf 2.2.1 control register (ctrl 11): address 0bh reset state 12h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 ndvsr6 ndvsr5 ndvsr4 ndvsr3 ndvsr2 ndvsr1 ndvsr0 ndvsr[6:0] represents the divisor. if nrst {2:0 ] =0 this register is ignored. 2.2.2 control register (ctrl 12): address 0ch reset state 00h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 nseq7 nseq6 nseq5 nseq4 nseq3 nseq2 nseq1 nseq0 nseq[7:0] represents the divisor sequence.
73m1903 data sheet ds_1903_032 12 rev. 2.1 2.2.3 control register (ct rl 13): address 0dh reset state 48h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 xtal1 xtal0 r eserved r eserved u nused nrst2 nrst1 nrst0 xtal[1:0] : 00 = xtal osc. bias current at 120 a 01 = xtal osc. bias current at 180 a 10 = xtal osc. bias current at 270 a 11 = xtal osc. bias current at 450 a if oscin is used as a clock input, ?00? setting should be used to save power(=167 a at 27.648 mhz ). nrst[3:0] represents the rate at which the nco sequence register is reset. the address 0d h must be the last register to be written to when effecting a change in pll. 2.2.4 control register (ctrl 14): address 0eh reset state 00h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 frcvco pwdnpll r eserved u nused u nused u nused u nused u nused frcvco = 1 forces vco as system clock. this is reset upon rst , pwdnpll = 1 or enfe = 0. both pwdnpll and enfe are delayed coming out of digital section to keep pll alive long enough to transition the system cl ock to crystal clock when frcvco is reset by pwdnpll or enfe. pwdnpll = 1 forces power down of pll analog section.
ds_1903_032 73m1903 data sheet rev. 2.1 13 3 c lock generation 3.1 crystal oscillator and pre - scaler nco the crystal oscillator operates over wide choice of crystals (from 9 mhz to 27 mhz) a nd it is first input to an nco based pre - scaler (divider) prior to being passed onto an on - chip pll appendix b . the intent of the pre - scaler is to convert the crystal oscillator frequency, fxtal, to a convenient frequency to be used as a reference frequency, fref, f or the pll. the nco pre - scaler requires a set of three numbers to be entered through the serial port (pseq[7:0], prst[2:0] and pdvsr[2:0]. the pll also requires 3 numbers as for programming; ndvsr[6:0], nseq[7:0], and nrst[2:0]. the following is a brief description of the registers that control the ncos, plls, and sample rates for the 73m1903 ic. the tables show some examples of the register settings for different clock and sample rates. a more detailed discussion on how these values are derived can be found in . 3.1.1 control register (ctrl 8): address 08h reset state 00h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 pseq7 pseq6 pseq5 pseq4 pseq3 pseq2 pseq1 pseq0 this corresponds to the sequence of divisor. if p rst{2:0] =0 this register is ignored . 3.1.2 control register (ctrl 9): address 09h reset state 0ah bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 prst2 prst1 prst0 pdvsr4 pdvsr3 pdvsr2 pdvsr1 pdvsr0 prst[2:0] represents the rate at which th e sequence regist er is reset. pdvsr[4:0] represents the divisor. 3.1.3 control register (ctrl 10): address 0ah reset state 22h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 ichp3 ichp2 ichp1 ichp0 fl kvco2 kvco1 kvco0 kvco2:0 represents the magnitude of kvco associated with the vco within pll . this indicates the center frequency of the vco when the control voltage is 1.6 volts and the slope of the vco freq versus control voltage (i.e., kvco.) . fl represents the pll loop filter settings. table 4 : kv co v ersus settings at vc=1.6 v, 25 c kvco2 kvco1 kvco0 fvco kvco 0 0 0 33 mhz 38 mhz/v 0 0 1 36 mhz 38 mhz/v 0 1 0 44 mhz 40 mhz/v 0 1 1 48 mhz 40 mhz/v 1 0 0 57 mhz 63 mhz/v 1 0 1 61 mhz 63 mhz/v 1 1 0 69 mhz 69 mhz/v 1 1 1 73 mhz 69 mhz/v
73m1903 data sheet ds_1903_032 14 rev. 2.1 tabl e 5 : pll power down addr. 00h bit 7 enfe addr. 0eh bit 6 pwdnpll pll 0 x pll power off 1 0 pll power on 1 1 pll power off table 6 : examples of nco settings fs (khz) dnco1 nnco1 psdiv psseq(7:0) psrs t =dnco1 - 1 dnco2 nnco2 plldiv pllseq(7:0) pllr st =dnco2 - 1 fvco (mhz) ppm fxtal(mhz)=27.0 7.2 8/125 15 11011010 7 5/96 19 xxx10000 4 33.177600 0 8.0 8/125 15 11011010 7 3/64 21 xxxxx100 2 36.864000 0 2.4*8/7*3 =8.22857142858 8/169 21 10000000 7 3/ 89 29 xxxxx110 2 37.917160* - 3 8.4 8/125 15 11011010 7 5/112 22 xxx10100 4 38.707200 0 9.0 8/125 15 11011010 7 1/24 24 xxxxxxxx 0 41.472000 0 9.6 8/125 15 11011010 7 5/128 25 xxx11010 4 44.236800 0 2.4*10/7*3 =10.2857142857 8/125 15 11011010 7 7/19 2 27 x1010110 6 47.396571 0 2.4*8/7*4 =10.9714285714 7/50 7 x1000000 6 8/107 13 10100100 7 50.557500* 23 11.2* 7/52 7 x1010100 6 5/71 14 xxx10000 4 51.611538* 38 12.0 8/125 15 11011010 7 1/32 32 xxxxxxxx 0 55.296000 0 12.8* 8/65 8 10000000 7 4/71 1 7 xxxx1110 3 58.984615* 38 2.4*10/7*4 =13.7142857143 7/80 11 x1010100 6 4/107 26 xxxx1110 3 63.196875* 23 14.4 8/125 15 11011010 7 5/192 38 xxx10100 4 66.355200 0 fxtal(mhz)=24.576 7.2 1/10 10 xxxxxxxx 0 2/27 13 xxxxxx10 1 33.177600 0 8.0 1/10 10 xxxxxxxx 0 1/15 15 xxxxxxxx 0 36.864000 0 2.4*8/7*3 =8.22857142858 4/35 8 xxxx1110 3 2/27 13 xxxxxx10 1 37.917257? 0 8.4 1/10 10 xxxxxxxx 0 4/63 15 xxxx1110 3 38.707200 0 9.0 1/10 10 xxxxxxxx 0 8/135 16 11111110 7 41.472000 0 9.6 1/10 10 xxxxxxxx 0 1 /18 18 xxxxxxxx 0 44.236800 0 2.4*10/7*3 =10.2857142857 3/28 9 xxxxx100 2 1/18 18 xxxxxxxx 0 47.3965714.. 0 2.4*8/7*4 =10.9714285714 4/35 8 xxxx1110 3 1/18 18 xxxxxxxx 0 50.5563429.. 0 11.2 1/10 10 xxxxxxxx 0 1/21 21 xxxxxxxx 0 51.609600 0 12 1/ 10 10 xxxxxxxx 0 2/45 22 xxxxxx10 1 55.296000 0 12.8 1/10 10 xxxxxxxx 0 1/24 24 xxxxxxxx 0 58.982400 0 2.4*10/7*4 =13.7142857143 1/7 7 xxxxxxxx 0 1/18 18 xxxxxxxx 0 63.19542? 0 14.4 1/10 10 xxxxxxxx 0 1/27 27 xxxxxxxx 0 66.355200 0 fxtal(mhz)=9.21 6 7.2 1/4 4 xxxxxxxx 0 5/72 14 xxx10100 4 33.177600 0 8.0 1/4 4 xxxxxxxx 0 1/16 16 xxxxxxxx 0 36.864000 0 8.4 1/4 4 xxxxxxxx 0 5/84 16 xxx11110 4 38.707200 0 9.0 1/4 4 xxxxxxxx 0 1/18 18 xxxxxxxx 0 41.472000 0 9.6 1/4 4 xxxxxxxx 0 5/96 19 xxx10000 4 44.236800 0 2.4*8/7*4 =10.9714285714 2/7 6 xxxxxx10 4 5/96 19 xxx10000 4 50.556343 0 11.2 1/4 4 xxxxxxxx 0 5/112 22 xxx10100 4 51.609600 0 12 1/4 4 xxxxxxxx 0 1/24 24 xxxxxxxx 0 55.296000 0
ds_1903_032 73m1903 data sheet rev. 2.1 15 fs (khz) dnco1 nnco1 psdiv psseq(7:0) psrs t =dnco1 - 1 dnco2 nnco2 plldiv pllseq(7:0) pllr st =dnco2 - 1 fvco (mhz) ppm 12.8 1/4 4 xxxxxxxx 0 5/128 25 xxx11010 4 58.982400 0 14.4 1/8 8 xxxxxxxx 0 5/288 57 xxx11010 4 66.355200 0 fxtal(mhz)=24.000 7.2 8/125 15 11011010 7 5/108 21 xxx11010 4 33.1776 0 8.0 2/25 12 xxxxxx10 1 5/96 19 xxx10000 4 36.864 0 2.4*8/7*3 =8.22857142858 4/73 18 xxxx1000 3 6/173 28 xx111110 5 37.91781* 15 8.4 8/125 15 11011010 7 5/126 25 xxx10000 4 38.7072 0 9.0 4/25 6 xxxx1000 3 5/54 10 xxx11110 4 41.472 0 9.6 8/125 15 11011010 7 5/144 28 xxx11110 4 44.2368 0 2.4*10/7*3 =10.2857142857 8/125 15 11011010 7 7/216 30 x1111110 6 47.39657 0 2.4*8/7* 4 =10.9714285714 6/59 9 xx111110 5 7/145 20 x1110110 6 50.5569* 12 11.2 8/125 15 11011010 7 5/168 33 xxx11010 4 51.6096 0 12.0 4/25 6 xxxx1000 3 5/72 14 xxx10100 4 55.296 0 12.8 8/125 15 11011010 7 5/192 38 xxx10100 4 58.9824 0 2.4*10/7*4 =13.71428 57143 5/61 12 xxx10000 4 8/257 32 10000000 7 63.19672* 21 14.4 7/73 10 x1010100 6 6/173 28 xx111110 5 66.35616* 15 fxtal(mhz)= 25.35 7.2 8/163 20 10010010 7 3/80 26 110 2 33.177914* 10 table 7 : clock generation register setting s for fxtal = 27 mhz reg address fs (khz) 8h 9h ah bh ch dh * ichp (a) kvco [2:0] 7.2 da ef 20 13 10 c4 8 0 8.0 da ef 31 15 04 c2 10 1 2.4*8/7*3 =8.22857142858 80 f5 41 1d 06 c2 12 1 8.4 da ef 31 16 14 c4 10 1 9.0 da ef 31 18 xx c0 10 1 9.6 da ef 32 19 1a c4 10 2 2.4*10/7*3 =10.2857142857 da ef 43 1b 54 c6 12 3 2 .4*8/7*4 =10.9714285714* 40 c7 23 0d a4 c7 8 3 11.2* 54 c7 23 0e 10 c4 8 3 12.0 da ef 24 20 xx c0 8 4 12.8* 80 e8 15 11 0e c3 6 5 2.4*10/7*4 =13.7142857143 54 cb 26 1a 0e c3 8 6 14.4 da ef 46 26 14 c4 12 6
73m1903 data sheet ds_1903_032 16 rev. 2.1 table 8 : clock gene ration register settings for fxtal = 24.576 m hz reg address fs (khz) 8h 9h ah bh ch dh* ichp (a) kvco [2:0] 7.2 xx 0a 10 0d 02 c1 6 0 8.0 xx 0a 11 0f xx c0 6 1 2.4*8/7*3 =8.22857142858 0e 68 11 0d 02 c1 6 1 8.4 xx 0a 21 0f 0e c3 8 1 9.0 xx 0a 21 10 fe c7 8 1 9.6 xx 0a 22 12 xx c0 8 2 2.4*10/7*3 =10.2857142857 04 49 23 12 xx c0 8 3 2.4*8/7 *4 =10.9714285714 0e 68 23 12 xx c0 8 3 11.2 xx 0a 23 15 xx c0 8 3 12 xx 0a 14 16 02 c1 6 4 12.8 xx 0a 15 18 xx c0 6 5 2.4*10/7*4 =13.7142857143 xx 07 16 12 xx c0 6 6 14.4 xx 0a 26 1b xx c0 8 6 table 9 : clock generation regis ter settings for fxtal = 9.216 mhz reg address fs (khz) 8h 9h ah bh ch dh* ichp (a) kvco [2:0] 7.2 xx 04 20 0e 14 c4 8 0 8.0 xx 04 31 10 xx c0 10 1 8.4 xx 04 31 10 1e c4 10 1 9.0 xx 04 31 12 xx c0 10 1 9.6 xx 04 32 13 10 c4 10 2 2.4*8/7*4 =10.9714285714 02 23 33 13 10 c4 10 3 11.2 xx 04 33 16 14 c4 10 3 12 xx 04 24 18 xx c0 8 4 12.8 xx 04 35 19 1a c4 10 5 14.4 xx 08 66 39 1a c4 16 6
ds_1903_032 73m1903 data sheet rev. 2.1 17 table 10: clock generation register settings for fxtal = 24.000 mh z reg address fs (khz) 8h 9h ah bh ch dh* ichp (a) kvco [2:0] 7.2 da ef 30 15 1a c4 10 0 8. 0 02 2c 31 13 10 c4 10 1 2.4*8/7*3 =8.22857142858 08 72 41 1c 3e c5 12 1 8.4 da ef 41 19 10 c4 12 1 9.0 08 66 11 0a 1e c4 6 1 9.6 da ef 42 1c 1e c4 12 2 2.4*10/7*3 =10.2857142857 da ef 43 1e 7e c6 12 3 2.4*8/7*4 =10.9714285714 3e a9 33 14 76 c6 10 3 11.2 da ef 53 21 1a c4 14 3 12 08 66 14 0e 14 c4 6 4 12.8 da ef 45 26 14 c4 12 5 2.4*10/7*4 =13.7142857143 10 8c 46 20 80 c7 12 6 14.4 54 ca 46 1c 3e c5 12 6 table 11 : clock generation register settings for fxtal = 25.35 m hz reg address fs (kh z) 8h 9h ah bh ch dh* ichp (a) kvco [2:0] 7.2 92 f4 50 1a 06 c2 14 0 0 1 xtal oscillator system clock nco kd up dn ichp control vco locked 2 2 fref fvco kvco control fxtal nco prescaler vco kvco pfd charge pump mux frcvco r1 c1 c2 loop filter control 2 figure 5 : clock generation
73m1903 data sheet ds_1903_032 18 rev. 2.1 4 modem receiver a differential receive signal applied at the rxap and rxan pins or the output signal at txap and txan pass through a multiplexer, which selects the inputs to the adc. in normal mode, rxap/rxan are selected. in analog loopback mode, txap/txan are selected. the dc bias for the rxap/rxan inputs is supplied from txap/txan through the external daa in normal conditions. (see appendix a ) it can be supplied internally, in the absence of the external daa, by setting rxpull bit in control register 2. the output of the multiplexer goes into a second - order continuous time, sallen - key, low - pass filter (aaf) with a 3 db point at approximately 40 khz . the filtered output signal is the input to an analog sigma - delta modulator (asdm), clocked at an over sampling frequency of 1.536 mhz for fs = 8 khz , which converts the analog signal to a serial bit stream with a pulse density that is proportional to the amplitude of the analog input signal. there are three gain con trol bits for the receive path. the rxgain bit in control register one results in a +20 db gain of the receive signal when set to a ?1?. this 20 db of gain compensates for the loss through the daa while on hook. it is used for caller id reception. this gain is realized in the front end of asdm. the other gain bits in control register 1, rxg1 :0, compensate for differences in loss through the receive path. table 12: receive gain rxg1 rxg0 receive gain setting 0 0 6 db 0 1 9 db 1 0 12 db 1 1 0 db the output of asdm is a serial bit stream that feeds three digital si nc 3 filters . each filter has a [sin(x)/x] 3 frequency response and provides a 16 bit sample every 288 clock cycles . the filters are synchronized so that there is one sample available after every 96 analog samples or at a rate of 16 khz for fs=8 khz . the output of the sinc 3 filter is a 17 bit, two?s compliment number representing the amplitude of the input signal. the sinc 3 filter, by virtue of holding action (for 96 sample period), introduces a droop in the passband that is later corrected for by a 48 ta p fir filter that follows. the maximum digital word that can be output from the filter is 0d800h . the minimum word is 12800h. the output of the sinc 3 filter is input to another 48 tap digital fir filter that provides an amplitude correction in the pas sband to the output of the sinc 3 filter as well as rejecting noise above fs/2 or 4 khz for fs=8 khz . the output of this filter is then decimated by a factor of 2; so, the final output is 16 bit, two?s complim ent samples at a rate of 8 khz. figure 6 and figure 7 depict the sinc 3 filter?s frequency response of asdm along with the 48 tap digital fir response that compensates for it and the resulting overall response of the re ceiver.
ds_1903_032 73m1903 data sheet rev. 2.1 19 figure 6 : overall receiver frequency response figure 7 : rx passband response it is important to keep in mind that the receive signal should not exceed 1.16 vpk - diff for proper performance f or rxg=11 (0 db). in particular, if the input level exceeds a value such that one?s density of rbs exceeds 99.5%, sinc 3 filter output will exceed the maximum input range of the decimation filter and consequently the data will be corrupted . also for stabi lity reasons, the receive signal should not exceed 1.16 vpk differentially. this value is set at around 65% of the full receive signal of 1.791 vpkdiff at rxap/rxan pins that ?would? corresponds to asdm putting out all ones. figure 8 and figure 9 show the spectrum of 1 khz tone received at rxap/rxan of 1.16 vpk - diff and 0.5 khz and 1.0 khz tones of 0.6 vpk - diff each, respectively for fs=8 khz . note the effect of fir supp ressing the noise above 4 khz but at the same time enhancing (in order to compensate for the passband droop of sinc 3 filter) it near the passband edge of 4 khz .
73m1903 data sheet ds_1903_032 20 rev. 2.1 figure 8 : rxd spectrum of 1 khz t one figure 9 : rxd spectrum of 0.5 khz , 1 khz , 2 khz , 3 khz and 3.5 khz t ones of equal amplitudes
ds_1903_032 73m1903 data sheet rev. 2.1 21 5 modem transmitter the modem transmitter begins with an 48 tap transmit interpolation filter (tif) that takes in the 16 - bit, two?s compliment numbers (txd) at sdin p in at fs=8 khz rate. it up - samples (interpolates) the data to 16 khz rate rejecting the images at multiples of 8 khz that exist in the original txd data stream and outputs 16 - bit, two?s compliment numbers to a digital sigma - delta modulator. the gain of t he interpolation filter is 0.640625 ( ? 3.8679 db ) at dc. the digital sigma - delta modulator (dsdm) takes 16 - bit, two?s compliment numbers as input and generates a 1?s bit stream which feeds into a d to a converter (dac1). the gain through dsdm is 1.0. ds dm takes 16 - bit, two?s compliment numbers as input and generates a 1?s bit stream that feeds into a d to a converter (dac1). dac1 consists of a 5 - tap fir filter and a first order switched capacitor low pass filter both operating at 1.536 mhz . it possesse s nulls at multiples of 384 khz to allow decimation by the succeeding filter. dac1?s differential output is fed to a 3rd - order switched - capacitor low pass filter (tlpf). the output of tlpf drives a continuous time smoothing filter. the sampling nature o f the transmitter leads to an additional filter response that affects the in - band signals. the response is in the form of sin(x)/x and can be expressed as 20*log [(sin(pi*f/fs))/(pi*f/fs)] where f = signal frequency and fs = sample frequency = 16 khz. figure 10 shows the frequency response of the transmit path from txd to txap/txan for a dc to 4 khz in - band signal including the effect of this sampling process plus those of dac1, tlpf and smflt. it is important to note that as txd is sampled at 8 khz , it be band - limited to 4 khz . figure 10 : frequency response of tx path for dc to 4 khz in band signal
73m1903 data sheet ds_1903_032 22 rev. 2.1 5.1 transmit levels the 16 - bit transmit code word written by the dsp to the digital sigma - d elta modulator (dsdm) (via tif) has a linear relationship with the analog output signal. so, decreasing a code word by a factor of 0.5 will result in a 0.5 ( - 6 db ) gain change in the analog output signal. the following formula describes the relationship between the transmit code word and the output level at the transmit pins (txap/txan): vout (v) = 2 * code/32,767 * dsdmgain * dacgain * vref * tlpfgain * smfltgain * freqfctr vout is the differential peak volt age at the txap and txan pins. code is th e 16 - bit, two?s compliment transmit code word written out by the dsp to the dsdm (via tif). the code word falls within a range of 32,767. for a sinusoidal waveform, the peak code word should be used in the formula to obtain the peak output voltage. ds dmgain is the scaling factor used on the transmit code word to reduce the possibility of saturating the modulator. this value is set to 0.640625 ( ? 3.555821 db ) at dc in the 48 tap transmit interpolation fi lter (tif) that precedes dsdm. dacgain is the gai n of the dac . the value dacgain is calculated based on capacitor values inside dac1 and dacgain =8/9=0.8889. the number 32,767 refers to the code word that generates an 82% ?1?s? pulse density at the output of the dsdm. as one can see from the formula, t he d to a conversion is dependent on the level of vref . also when txbst1 bit is set, vref is increased from 1.36 v to 1.586 v to allow higher transmit level or 16.6% increase in gain . this bit is intended for enhancing the dtmf transmit level and should not be used in data mode . tlpfgain is the gain of tlpf and nominally equals to 0.00 db or 1.0. smfltgain is the gain of smflt and nominally equal to 1.445 or 3.2 db. when txbst0 bit is set, the gain is further increased by 1.65 db (1.21) for the total of 4.85 db. this is to accommodate greater hybrid insertion loss en countered in some applications. freqfctr shows dependency of the entire transmit path on frequency. see figure 10. with the transmit code word o f +/ - 32,767, the nominal differential swing at the transmit pins at dc is: vout (v) = 2 * code/32,767 * dsdmgain * dacgain * vref * tlpfgain * smfltgain * freqfctr = 2 * 32,767/32767 * 0.6640625 * 0.8889 * 1.36 * 1.0 * 1.4454 * 1.0 = 2.31vpk di ff. when txbst1 bit is set, vout (v) = 1.166 * 2.31= 2.693 vpk diff. when txbst0 bit is set, vout (v) = 1.21 * 2.31= 2.795 vpk diff , i f not limited by power supply or internal reference . when both txbst1 and txbst0 are set to 1, vout (v) = 1.166 * 1.21 * 2.31 = 3.259 vpk diff.
ds_1903_032 73m1903 data sheet rev. 2.1 23 5.2 transmit power - dbm to calculate the analog output power, the peak voltage is calculated and the peak to rms ratio (crest factor) must be known . the following formula is used to calculate the output pow er, in dbm referenced to 600 . pout (dbm) = 10 * log [ ( vout (v) / cf ) 2 / ( 0.001 * 600 ) ] the following example demonstrates the calculation of the analog output power given a 1.2 khz fsk tone (sine wave) with a peak code word value of 11,878 sent out by the dsp. the different ial output voltage at txap - txan will be: with freqfctr = 1.02, (see figure 10 ) vout (v) = 2 * (11,878/32,767) * 0.6640625 * 0.888 9 * 1.36 * 1.0 * 1.4454 * 1.02 = 0.841 v pk . the output signal power will be: pout (dbm) = 10 * log [(0.841 / 1.41) 2 / (0.001 * 600) ] = - 2.29 dbm . table 13: peak to rms ratios for various modulation types transmit type crest f actor max line l evel v.90 4.0 - 12 dbm qam 2.31 - 9 dbm dpsk 1.81 - 9 dbm fsk 1 .41 - 9 dbm dtmf 1.99 - 5.7 dbm 5.3 control register (ctrl1): address 00h reset state 08h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 enfe u nused txbst1 txbst0 txdis rxg1 rxg0 rxgain enfe 1 = enable the digital filters and analog front end. 0 = disable the analog blocks shut off the clocks to the digital and an alog receive/transmit circuits. txbst1 1 = add a gain of 1.335 db (16.6%) to the transmitter; also the common mode voltage of the transmit path is increased to 1.375 v. this is intended f or enhancing dtmf transmit power only and should not be used in data mode. 0 = no gain is added txbst0 1 = a gain of 1.65 db (21%) is added to the transmitter 0 = the gain of the transmitter is nominal txdis 1 = tri - state the txap and txan pins, pro vides a bias of vbg into 80 k ? for each output pin rxg1:0 these bits contr ol the receive gain as shown in table 12. rxgain 1 = increase the gain of the receiver by 20 db.
73m1903 data sheet ds_1903_032 24 rev. 2.1 5.4 control register (ctrl2): address 01h reset state 00h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 tmen diglb analb intlb ckouten rxpull spos hc tmen 1 = enable test modes. diglb 1 = tie the serial bit stream from the digital transmit filter output to the digital receive filter inpu t. digital loopback analb 1 = tie the analog output of the transmitter to the analog input of the receiver . analog loopback intlb 1 = tie the digital serial bit stream from the analog receiver output to the analog transmitter input. int ernal loopback ckouten 1 = enable the clkout output; 0 = clkout tri - stated. for test purposes only; do not use in normal operation. rxpull 1 = pulls dc bias to rxap/rxan pins, through 100 k ? each, to vref, to be used in testing rx path. 0 = no dc b ias to rxap/rxan pins . spos 1 = control frames occur after one quarter of the time between data frames has elapsed. 0 = control frames occur half way between data frames. hc 1 = fs is under hardware control, bit 0 of data frames on sdin is bit 0 of the transmit word and control frames happen automatically after every data frame. 0 = fs is under software control, bit 0 of data frames on sdin is a control frame request bit and control frames happen only on request. 5.5 revision register: address 06h res et state 30h bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 rev3 rev2 rev1 rev0 unused r eserved r eserved r eserved bits 7 - 4 contain th e revision level of the 73m1903 device. the rest of this register is for chip development purposes only and is not int ended for customer use. do not write to shaded locations.
ds_1903_032 73m1903 data sheet rev. 2.1 25 6 test modes there are two loop back test modes that affect the configuration of the analog front end. the internal loop back mode connects the serial bit stream generated by the analog receiver to the input of the analog transmitter. this loop back mode is similar to a remote analog loop back mode and can be used to evaluate the operation of the analog circuits. when using this loop back mode, the txan/txap pins should not be externally coupled t o the rxap/rxan pins . set bit 4 (intlb) in register 1h (ctrl2) to enter this loop back mode. the second loop back test mode is the external loop back mode, or local analog loop back mode. in this mode, the analog transmitter outputs are fed back into th e input of the analog receiver. set bit 5 (analb) in register 1h (ctrl2) to enter this loop back mode. in this mode, tbs must be kept to below a value that corresponds to less than 1.16 v /2.31 v x - 6 db = 25% of the full scale code of +/ - 32768 at txd i n order to ensure that the receiver is not overdriven beyond the maximum of 1.16 v pkpk diff for rxg=11(0 db ) setting. see table 16 for the maximum allowed transmit levels. check the transmitted data against received data via serial interface. this tests the functionality of essentially all blocks, both digital and analog, of the chip. there is a third loopback mode that bypasses the analog circuits entirely. digital loop back forces the transmitter digital serial bit stream (from dsdm) to be routed i nto the digital receiver?s sinc 3 filters. set bit 6 (diglb) in register 1h (ctrl2 ) to enter this loop back mode. 7 power saving modes the 73m1903 has only one power conservation mode. when the enfe, bit 7 in register 0h, is zero the clocks to the filters and the analog are turned off. the transmit pins output a nominal 80 k ? impedance. the clock to the serial port is running and the gpio and other registers can be read or updated.
73m1903 data sheet ds_1903_032 26 rev. 2.1 8 electrical specifications 8.1 absolute maximum ratings operation above maximum rating may permanently damage the device. parameter rating supply voltage - 0.5 v to +4.0 v pin input voltage (except oscin) - 0.5 v to 6.0 v pin input voltage (oscin) - 0.5 v to vdd + 0.5 v 8.2 recommended operating conditions parameter rating supply vol tage (vdd) with respect to vss 3.0 v to 3.6 v oscillator frequency 24.576 mhz 100ppm operating temperature - 40 c to +85 c
ds_1903_032 73m1903 data sheet rev. 2.1 27 8.3 digital specifications 8.3.1 dc characteristics parameter symbol conditions min nom max unit input low voltage vil - 0.5 0.2 * vdd v input high voltage (except oscin) vih1 0.7 vdd 5.5 v input high voltage oscin vih2 0.7 vdd vdd + 5.5 v output low voltage (except oscout, fs , sclk, sdout) vol iol = 4 ma 0.45 v output low voltage oscout volosc iol = 3.0 ma 0.7 v output low v oltage fs,sclk,sdout vol iol = 1 ma 0.45 v output high voltage (except oscout, fs , sclk, sdout) voh ioh = - 4 ma vdd - 0.45 v output high voltage oscout vohosc ioh = - 3.0 ma vdd - 0.9 v output high voltage fs , sclk, sdout voh ioh = - 1 ma vdd - 0.45 v input low leakage current (except oscin) iil1 vss < vin < vil1 1 a input high leakage current (except oscin) iih1 vih1 < vin < 5.5 1 a input low leakage current oscin iil2 vss < vin < vil2 1 30 a input high leakage current oscin iih2 vih2 < vin 73m1903 data sheet ds_1903_032 28 rev. 2.1 8.3.2 ac timing table 14: serial i/f timing parameter min nom max unit sclk period (tsclk) (fs=8 khz) ? 1/2.048 mhz ? ns sclk to fs delay (td1) ? mode1 ? ? 20 ns sclk to fs delay (td2) ? mode1 ? ? 20 ns sclk to sdout delay (td3) (with 10pf load) ? ? 20 ns setup time sdin to sclk (tsu) 15 ? ? ns hold time sdin to sclk (th) 10 ? ? ns sclk to fs delay (td4) ? mode0 ? ? 20 ns sclk to fs delay (td5) ? mode0 ? ? 20 ns sclk fs (mode1) sdout sdin td1 td2 tsu td3 td5 fs (mode0) td4 rx0 rx15 rx14 rx1 th tx15 tx14 tx1 tx0 tsclk figure 11 : serial port data timing
ds_1903_032 73m1903 data sheet rev. 2.1 29 8.4 analog specifications 8.4.1 dc specifications vref should be connected to an external bypass capacitor with a minimum value of 0.1 f . this pin is not intended for any other external use. table 15: reference voltage specifications parameter test condition min nom max units vref vdd= 3.0 v - 3.6 v. 1.36 v vref noise 300hz - 3.3 khz - 86 - 80 dbm 600 vref psrr 300hz - 30 khz 40* db 8.4.2 ac specifications table 16 shows the maximum transmit levels that the output drivers can deliver before distortion through the daa starts to become significant. the loss though the daa t ransmit path is assumed to be 7 db. the signals presented at txap and txan are symmetrical. the transmit levels can be increased by setting either txbst0 (+1.5 db ) or/and txbst1 (+0.83 db ) for the combined total gain of 2.33 db . these can be used where higher - level dtmf tones are required. table 16 : maximum transmit levels transmit type maximum different line level (dbm0) maximum single - ended level at txa pins (dbm) peak to rms ratio s ingle - ended rms voltage at txa pins (v) single - ended peak voltage at txa pins (v) vpa=2.7 v to 3.6 v . all rms and peak voltages are relat ive to vref. v.90 - 12.0 - 11.0 4 0.2175 0.87 qam - 7.3 - 6.3 2.31 0.377 0.87 dpsk - 5.1 - 4.1 1.81 0.481 0.87 fsk - 3.0 - 2.0 1.41 0.616 0.87 dtmf (high tone) - 7.8 - 6.8 1.41 0.354 0.500 dt mf (low tone) - 9.8 - 8.8 1.41 0.283 0.400
73m1903 data sheet ds_1903_032 30 rev. 2.1 8.5 performance 8.5.1 receiver tabl e 17 : receiver performance specifications parameter test conditions min nom max units input impedance measured at rxap/n relative to vref rxpull=hi 230 k? measured at rxap/n relative to vref rxpull=lo 1.0 m ? receive gain boost rxgain = 1; 1 khz ; rxap/n=0.116 v pk -diff gain measured relative to rxgain=0 rxgain=1 for fs=8 khz rxgain =1 for fs=12 khz rxgain =1 for fs=14.4 khz 17.0 16.2 15.7 18.5 17.4 17.2 20.0 18.7 18.7 db db db total harmonic distortion (thd) thd = 2 nd and 3 rd harmonic. rxgain =1 64 70 rxg gain gain measured re lative to rxg[1:0]=11 (0 db ) @1 k hz rxg[1:0]=00 rxg[1:0]=01 rxg[1:0]=10 5.8 8.8 11.8 6 9 12 6.2 9.2 12.2 db db db passband gain input 1.16 v pk -diff at rxa . measure gain at 0.5 khz , and 2 khz . normalized to 1 khz . gain at 0.5 khz gain at 1 khz (normalized) gain at 2.0 khz - 0.29 - 0.067 - 0.042 0.000 0.183 0.21 0.43 db db db input offset short rxap to rxan . measure input voltage relative to vref - 30 0 30 mv sigma - delta adc modulation gain normalized to vbg=1.25 v . includes the effect of aaf( - 0.4 db ) with bits 1, 0 of ctrl2 register (01h) = 00. 41 v/bit maximum analog signal level at rxap/rxan peak voltage measured differentially across rxap/rxan. 1.16 v pk -diff total harmonic distortion (thd) 1 khz 1.16 v pk -diff at rxa with rxg=11 thd = 2 nd and 3 rd harmonic. 80 85 db noise transmit v.22bis low band; fft run on adc samples . noise in 0 to 4 khz band - 85 - 80 dbm crosstalk 0 db m 1000hz sine wave at txap; fft on rx adc samples, 1 st four harmonics reflected back to receiver inputs. - 100 db note: rxg[1:0] and rxgain are assumed to have settings of ?0? unless they are s pecified otherwise.
ds_1903_032 73m1903 data sheet rev. 2.1 31 8.5.2 transmitter table 18: transmitt er performance specifications parameter test condition min nom max units dac gain (transmit path gain) c ode word of 32,767 @1 khz ; txbst0=0; txbst1=0 70 v/bit dc offset ? di fferential mode across txap and txan for dac input = 0 - 100 100 mv dc offset - common mode average of txap and txan for dac input = 0; relative to vref - 80 80 mv txbst0 gain code word of 32,767 @1 khz ; relative to txbst0=0; txbst1=0 1.65 db txbst 1 gain code word of 32,767 @1 khz ; relative to txbst0=0; txbst1=0 1.335 db total harmonic distortion (thd) code word of 32,767 @1 khz ; relative to txbst0=0;txbst1=0 thd = 2 nd and 3 rd harmonic. - 75 - 85 db code word of ( 32,767*0.8) @1 kh z; relative to txbst0=0;txbst1=0 thd = 2 nd and 3 rd harmonic. - 80 - 85 db 1200 ?5hvlvwru across tnan/txap code word of ( 32,767*0.9) @1 khz ; relative to txbst0=1;txbst1=1 thd = 2 nd and 3 rd harmonic. - 60 - 70 db code word of 32,767 @1 khz ; relativ e to txbst0=1;txbst1=1 thd = 2 nd and 3 rd harmonic - 70 intermod distortion at output (txap - txan): dtmf 1.0 khz , 1.2 khz sine waves, summed 2.0 v pk ( - 2 db m tone summed with 0 db m tone) refer to tbr 21 specifications for description of complete requirem ents. 70 db below low tone idle channel noise 200 hz - 4.0 khz 110 9 psrr - 30 dbm signal at vpa 300 hz ? 30khz 40 db passband ripple 300 hz - 3.2khz - 0.125 0.125 db transmit gain flatness code word of 32,767 @1 khz . measure gain at 0.5 khz, and 2 k hz relative to 1 khz . gain at 0.5 khz gain at 1 khz (normalized) gain at 2.0 khz gain at 3.3 khz 0.17 0 0.193 - 0.12 db db db db
73m1903 data sheet ds_1903_032 32 rev. 2.1 parameter test condition min nom max units txap/n output impedance differentially (txdis=1) txdis=1 measure impedance differentially between txap and txan. 160 k? txap/n common output offset (txdis=1) txdis=1 short txap and txan. measure the voltage respect to vbg. - 20 0 20 mv note: txbst0 and dtmfbs are assumed to have setting 0?s unless they are specified otherwise.
ds_1903_032 73m1903 data sheet rev. 2.1 33 9 p inouts 9.1 32- pin qfn pinout figure 12 : 32 - pin qfn pinout table 19 : 32 - pin qfn pin definitions pin name pin name 1 vnd 17 vnpll 2 vpd 18 oscout 3 gpio0 19 oscin 4 gpio1 20 vppll 5 gpio2 21 clkout 6 gpio3 22 vnd 7 fs 23 gpio4 8 sclk 24 gpio5 9 rst 25 vpd 1 0 vpa 26 n/c 11 txan 27 type 12 txap 28 sckmode 13 vref 29 sdin 14 rxan 30 gpio6 15 rxap 31 gpio7 16 vna 32 sdout 6 7 8 9 5 4 3 2 1 17 18 19 20 24 23 22 21 1 0 1 1 1 2 1 3 1 4 1 5 1 6 3 2 3 1 3 0 2 9 2 8 2 7 2 6 2 5 vnd vpd gpio 0 gpio 1 gpio 2 gpio 3 fs sclk gpio 5 gpio 4 vnd n / c vppll oscin oscout vnpll r s t v p a t x a n t x a p v r e f r x a n r x a p v n a teridian 73m 1903 v p d s d o u t g p i o 7 g p i o 6 s d i n s c k m o d e n / c t y p e
73m1903 data sheet ds_1903_032 34 rev. 2.1 9.2 20- pin tssop pinout 73m1903 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 sdout vpd sclk vref vpa txap rxan type vppll vnd oscout rxap vna vnpll sdin txan fs vnd rst oscin figure 13 : 20 - pin tssop pin out table 20: 20 - pin tssop pin definitions pin name pin name 1 sdout 11 rxan 2 vnd 12 rxap 3 vpd 13 vna 4 fs 14 vnpll 5 sclk 15 oscout 6 vref 16 oscin 7 rst 17 vppll 8 vpa 18 vnd 9 txan 19 type 10 txap 20 sdin
ds_1903_032 73m1903 data sheet rev. 2.1 35 r2 20k r48 210, 1% r49 210, 1% r16 100 sdo hook f rom host r17 38.3k, 1% r20 61.9k, 1% r22 38.3k, 1% r23 61.9k, 1% c3 0.15uf vcca sdi 27mhz or other sy sclk fs\ sclk + c7 10uf c11 0.1uf c13 0.1uf vccd c21 0.1uf c4 2.2nf u1 73m1903-20vt sdout 1 vnd 2 vpd 3 fs 4 sclk 5 vbg 6 rst 7 vpa 8 txan 9 txap 10 rxan 11 rxap 12 vna 13 vnpll 14 oscout 15 oscin 16 vpll/ppd 17 vnd 18 sclkm 19 sdin 20 reset\ reset ti p ring - + br1 hd04 4 1 3 2 isolation barrier u2 tlp627 1 2 4 3 c22 220pf, 250v c20 220pf, 3kv c23 220pf, 3kv l2 nlv32t-4r7 e1 tisp4350t3bjr bourns thy ristor 1 2 t1 mit4115v sumida 1 4 2 3 c19 0.22uf 250v r9 63k l1 nlv32t-4r7 f1 mf-r015/600 bourns ptc f use + c9 3.3uf c10 0.1uf vccd 10 73m1903 schematic and bill of material figure 14 : 7 3m1903 schematic
73m1903 data sheet ds_1903_032 36 rev. 2.1 table 21 : bill of materials item qty reference part sources 1 1 br1 400 v, 500 ma bridge rectifier diodes, inc, on semi 2 1 c3 0.15 f 25 v panasonic, a vx, tdk 3 1 c4 2.2 nf 25 v panasonic, avx, tdk 4 1 c7 10 f 6.3 v panasonic, avx, tdk 5 1 c9 3.3 f 6.3 v panasonic, avx, tdk 6 4 c10,c11,c13,c21 0.1 f 25 v panasonic, avx, tdk 7 1 c19 0.22 f 250 v panasonic, avx, tdk 8 2 c20,c23 220 pf, 3 kv avx, tdk, yageo 9 1 c22 220 pf, 250 v vishay, murata, tdk 10 1 e1 275 v, 200 a bourns, tyco, littel fuse 11 1 f1 150 ma, 600 v bourns, tyco, vishay 12 2 l1,l2 4.7 h, 200 ma tdk, allied 13 1 r2 20 k panasonic, yageo, vishay 14 1 r9 63 k panasonic, yageo, vishay 15 1 r16 100 panasonic, yageo, vishay 16 2 r17,r22 38.3 k, 1% panasonic, yageo, vishay 17 2 r20,r23 61.9 k, 1% panasonic, yageo, vishay 18 2 r48,r49 210 k , 1% panasonic, yageo, vishay 19 1 t1 600 ? , 100 madc, 1:1 sumida, datatronics, allied 20 1 u1 73m1903 - 20vt teridian 21 1 u2 darlington optocoupler, 300 v vceo toshiba, solid state optronics
ds_1903_032 73m1903 data sheet rev. 2.1 37 11 mechanical specifications 11.1 32- pin qfn mechanical drawings dimensions in mm. 2.5 5 2.5 5 top view 1 2 3 figure 15 : 32 - pin qfn mechanical specifications 0.85 nom. / 0.9max. 0.00 / 0.005 0.20 ref. seating plane side view 0.2 min. 0.35 / 0.45 1.5 / 1.875 3.0 / 3.75 0.18 / 0.3 bottom view 1 2 3 0.25 0.5 0.5 0.25 3.0 / 3.75 1.5 / 1.875 0.35 / 0.45 chamfered 0.30
73m1903 data sheet ds_1903_032 38 rev. 2.1 11.2 20- pin tssop mechanical drawings dimensions in mm. figure 16 : 20 - pin tssop mechanical specifications
ds_1903_032 73m1903 data sheet rev. 2.1 39 12 ordering information table 22 : ordering information part description order number package mark 73m1903 32 - lead qfn lead free 73m1903 - im/f 73m1903 - m 73m1903 32 - lead qfn, tape and reel, lead free 73m1903 - imr/f 73m1903 - m 73m1903 20 - lead tssop lead free 73m1903 - ivt/f 73m 190ivt 73m1903 20 - lead tssop, tape and reel, lead free 73m1903 - ivtr/f 73m190ivt
73m1903 data sheet ds_1903_032 40 rev. 2.1 appendix a ? 73m1903 daa resistor calculation guide the following procedure is used to approximate the component values for the daa . the optimal values will be somewhat different due to the effects of the reactive components in the daa (this is a dc approximation). simulations with the reactive components accurately modeled will yield optimal values. the procedures for calculating the component values in the daa are as follows. first set up r1. the daa should be designed to reflect 600 ? when looking in at tip/ring. if the transformer is 1 to 1, the holding coil and ring detect circuit are high impedance, cblock is a high value so in the frequency band of interest it is negligible, the sum of r2 and r3 is much greater than r1, and the output impedance of the drivers driving txap/txan are low then: rin 2 r1 rw rohswitch 2 rbead rw is the sum of the winding resistance of both sides of the transformer. measure each side of the transformer with an ohmmeter and sum them. rohswitch is the on resistance of the off hook switch. mechanical relay switches are ignored, but solid state relays sometimes have an appreciable on resistance. rbead is the dc resistance of whatever series rf blocking devices m ay be in the design. for rin equal to 600 ?: r1 600 rw rohswitch 2 rbead 2 to maximize thl (trans - hybrid loss), or to minimize the amount of transmit signal that shows up back on the receive pins . the rxap/rxan pins get their dc bias from the txap/txan pins. by capacitively coup ling the r3 resistors with the c1 caps, the dc offset is minimized from the txap/txan to the rxap/rxan because the dc offset will be divided by the ratio of the r1 resistors to the winding resistance on the one side of the transformer. next make the sum o f r2 + r3 much h igher than 600 ?. make sure they are lower than the input impedance of the rxap/rxan pins; otherwise they can move the frequency response of the input filter. so let r2 + r3 = 100 k.
ds_1903_032 73m1903 data sheet rev. 2.1 41 r3 100 k 1 rwtot 600 1200 where rwtot rw rohswitch 2 rbead . r2 100 k r3 use 1% resistors for r1, r2, and r3 . to select the valu e for c1, make the z ero at around 10 hz. 1 2 . 100 . k c1 . 10 c1 1 2 . 100 . k 10 . c1 0.15 uf the blocking cap cblock should also have the same frequency response, but due to the low impedance, its value will be much higher, usually requiring a polarized cap. a blocking cap may also be needed on the modem side of the transformer if the dc offset current of the transmit pins will exceed the current rating for a dry transformer circuit . cblock 1 2 . 600 . 10 . cblock 27 uf if you are using a wet transformer design, as in the following figure: the only difference is that the blocking capacitor, cblock, it is removed. all other equations still hold true. trans - hybrid loss (thl) trans - hybrid loss is by definition the loss of transmit signal from tip/ring to the receive inputs on the modem ic. this definition is on ly valid when driving a specific phone line impedance. in reality, phone line impedances are never perfect, so this definition isn?t of much help. instead, as an alternate definition that helps in analysis for this modem design, thl is the loss from the transmit pins to the receive pins.
73m1903 data sheet ds_1903_032 42 rev. 2.1 a ppendix b ? crystal oscillator the crystal oscillator is designed to operate over wide choice of crystals (from 9 mhz to 27 mhz ) . the crystal oscillator output is input to an nco based pre - scaler (divider) prior to b eing passed onto an on - chip pll . the intent of the pre - scaler is to convert the crystal oscillator frequency, fxtal, to a convenient frequency to be used as a reference frequency, fref, for the pll. a set of three numbers ? pdvsr (5 bit), prst (3 bit) and p seq (8 bit) must be entered through the serial port as follows: pdvsr = integer [fref/fxtal]; prst = denominator of the ratio (fref/fxtal) minus 1 when it is expressed as a ratio of two smallest integers = nnco1/dnco1; pseq = divide sequence fxtal mux count ctrl overflow counter pdvsr pdvsr +1 sequence register rst sequence counter fref pseq[7:0] prst[2:0] figure 17 : nco block diagram n ote that in all cases, pre - scaler should be designed such that pre - scaler output frequency, fref, is in the range of 2 ~ 4 mhz . in the first example below, the exact divide ratio required is fxtal/fref = 15.625 =125/8. if a divide sequence of { 16, 16, 15, 16, 16, 15, 16, 15} is repeated, the effective divide ratio would be exactly 15.625. consequently, pdvsr of 15, the length of the repeating pattern, prst = 8 ? 1 =7, and the pa ttern, {1,1,0,1,1,0,1,0}, where 0 means pdvsr, or 15, and 1 means pdvsr +1, or 16 must be entered as below. example 1: fxtal = 27 mhz , fref = 1.728 mhz . pdvsr = integer [fxtal/fref] = 15 =0fh prst[2:0] = 8 ? 1 = 7 from fxtal/fref = 15.625 =125/8; pse q = 16, 16, 15, 16, 16, 15, 16, 15 => {1,1,0,1,1,0,1,0} =dah. in the second example, fxtal/fref =4.0. this is a constant divide by 4. thus pdvsr is 4, prst = 1 ? 1 =0 and pseq = {x,x,x,x,x,x,x,x).
ds_1903_032 73m1903 data sheet rev. 2.1 43 example 2: fxtal = 18.432 mhz , fref = 2.304 mhz . pdvsr = integer [fxtal/fref] = 8 = 8h; prst[2:0] = 1 - 1 = 0 from fref/fxtal = 18.43 2/2.304 = 8/1; pseq = {x,x,x,x,x,x,x,x} = xxh example 3: fx tal = 24.576 mh z , fref = 2.4576 mh z. pdvsr = integer [ fxtal/fref] = 10 = ah; prst[2:0] = 1 - 1 = 0 from fref/fxtal = 24.576/2.4576 = 10/1; pseq = {x,x,x,x,x,x,x,x} = xxh it is also important to note that when fxtal/fref is an integer the output of the pre - scaler is a straight frequency divider (example 2). as such there will be no jitter generated at fref. however if fxtal/fref is a fractional number, fref, at the output of the pre - scaler nco would be exact only in an average sense (example 1) and there will be a certain amount of fixed pattern (repeating) jitter associated with fref which can be filtered out by the pll that follows by appropriately programming the pll. it is important to note, however, that the fixed pattern jitter does not degrade the performance of the sigma delta modulators so long as its frequency is >> 4 khz . pll vco kvco nco prescaler pfd charge pump nco kd up dn r1 c1 c2 divide by 2/1 ichp control 3 3 fref kvco control figure 18 : pll block diagram 1903b has a built in pll circuit to allow an operation over wide range of fs. it is of a conventional design with the exception of a n nco based feedback divider. se e figure 18 . the architecture of the 73m1903 dictates that the pll output frequency, f vco, be related to the sampling rate, fs, by fvco = 2 x 2304 x fs. the nco must function as a div ider whose divide ratio equals fref/f vco. just as in the nco pr e - scaler, a set of three nu mbers ? ndvsr (7 bits), nrst (3 bit ) and nseq ( 8 bits ) must be entered through a serial port to effect this divide: ndvsr = integer [ fref/fxtal ] ; nr st = denominator of the ratio (fvco/fref), d nco1, minus 1, when it is expr essed as a ra tio of two smallest integers = nnco1/d nco1; nseq = divide sequence example 1: fs = 7.2 khz or fvco = 2 x 2304 x 7.2 khz =33.1776 mhz , fref = 1.728 mhz . ndvsr = integer [ fvco/fref ] = 19 nrst = 5 ? 1 = 4 from fvco/fref = 19.2 = 96/5; nseq = 19, 19, 19, 19, 20 => {0,0,0,0,1} =xxx00001 = 01h.
73m1903 data sheet ds_1903_032 44 rev. 2.1 example 2: fs = 8.0 khz or fvco = 2 x 2304 x 8 khz =36.864 mhz , fref = 2.304 mhz . ndvsr = integer [fvco/fref] = 16 = 10h; nrst= 1 - 1 = 0 from fvco/fref = 16/1; nseq = {x,x,x,x,x,x,x,x} = xxh. e xample 3: fs = 9.6 khz or fvco = 2 x 2304 x 9.6 khz =44.2368 mhz , fref = 2.4576 mhz . ndvsr = integer [fvco/fref] = 18 = 16h; nrst= 1 - 1 = 0 from fvco/fref = 18/1; nseq = {x,x,x,x,x,x,x,x} = xxh. it is important to note that in general the nco based feedb ack divider will generate a fixed jitter pattern who se frequency components are at fref/a ccreset2 and its integer multiples. the overall jitter frequency will be a nonlinear combination of jitte rs from both pre - scaler and pll nco . the fundamental frequency component of this jitte r is at fref/prst/n rst. the pll parameters should be selected to remove this jitter. three separate controls are provided to fine tune the pll as shown in the followin g sections. to ensure quick settli ng of pll , a feature was designed into the 73m1903 where i chp is kept at a higher value until lokdet becomes active or f rcvco bit is set to 1, w hichever occurs first. thus pll is guaranteed to have the settling time of less than one frame syn ch period aft er a new set of nco parameters had been writte n to the appropriate registers. the serial port register writes for a particular sample rate should be done in sequence starting from regis ter 08h ending in register 0dh. 0dh register should be the last one t o be written to. this will be followed by a write to the next register in sequence (0 eh) to force the transition of sysclk from xtal to p llclk. upon the system reset , the system clock is reset to f xtal/9. t he system clock will remain at f xtal/9 until th e host forces the transition, but no sooner the second frame synch period after the write to 0dh. when this happens, the system clock will transition to pllclk without any glitches through a specially designed deglitch mux. examples of nco s ettings exam ple 1: crystal frequency = 24.576 mhz ; desired sampling rate, fs = 13.714 khz (=2.4 khz x 10/7 x 4) step 1. first compute the required vco frequency, fvco, corresponding to fs = 2.4 khz x 10/7 x 4 = 13.714 khz , or fvco = 2 x 2304 x fs = 2 x 2304 x 2.4 kh z x 10/7 x 4 = 63.19543 mhz . step 2. express the required vco frequency divided by the crystal frequency as a ratio of two intege rs. this is initially given by : mhz fxtal fvco 576 . 24 4 10/7 2.4khz 2304 2 / ? ? ? ? = . after a few rounds of simplification this ratio reduces to: 18 1 7 1 dnco2 nnco2 dnco1 nnco1 ) 1 18 ( ) 7 1 ( 7 18 / = = ? = = fxtal fvco
ds_1903_032 73m1903 data sheet rev. 2.1 45 where nnco1 and nnco2 must be < or equal to 8. the ratio, nnco1/dnco1 = 1/7, is used to form a divide ratio for the nco in prescaler and nnco2/dnco2 = 1/18 for the nco in the pll. prescaler nco: from nnco1/dnco1 = 1/7, pdvsr = intege r [ dnco1/nnco1 ] = 7; prst[2:0] = nnco1 ? 1 = 0; this means no fractional divide. it always does 7. thus pseq becom es ?don?t care? and is ignored. pseq = {x,x,x,x,x,x,x,x} = xxh. pll nco: from nnco2/dnco2 = 1/18, ndvsr = integer [ dnco2/nnco2 ] = 18; nrst[2:0] = nnco2 ? 1 = 0; this means no fractional divide. it always does 18. thus pseq becom es ?don?t care? and is ignored. nseq = {x,x,x,x,x,x,x,x} = xxh. example 2: crystal frequency = 24.576 mhz ; desired sampling rate, fs = 10.971 khz =2.4 khz x 8 /7 x4 step 1. first compute the required vco frequency, fvco, corresponding to fs = 2.4 khz x 8/7 x 4 =10.971 khz . fvco = 2 x 2304 x fs = 2 x 2304 x 2.4 khz x 8/7 x 4 = 50.55634 mhz . step 2. express the required vco frequency divided by the crystal fr equency as a ratio of two intege rs. this is initially given by : mhz fxtal fvco 576 . 24 4 8/7 2.4khz 2304 2 / ? ? ? ? = . after a few rounds of simplification this ratio reduces to: 18 1 35 4 dnco2 nnco2 dnco1 nnco1 ) 1 18 ( ) 35 4 ( / = = ? = fxtal fvco , where nnco1 and nnco2 must be < or equal to 8. the ratio, nnco1/dnco1 = 4/35, is used to form a divide ratio for the nco in pre - scaler and nnco2/dnco 2 =1/18 for the nco in the pll. pre - scaler nco: from nnco1/dnco1 = 4/35, pdvsr = integer [ dnco1/nnco1 ] = 8; prst[2:0] = nnco1 ? 1 = 3; dnco1/nnco1 = 35/4 = 8.75 suggests a divide sequence of { 9, 9, 9, 8}, or pseq = {x,x,x,x,1,1,1,0} = xdh. pll nco: from nnco2/dnco2 = 1/18, ndvsr = integer [ dnco2/nnco2 ] = 18; nrst[2:0] = nnco2 ? 1 = 0; this means no fractional divide. it always does 18. thus pseq becomes ?don?t care?. nseq = {x,x,x,x,x,x,x,x} = xxh.
73m1903 data sheet ds_1903_032 46 rev. 2.1 example 3: crystal frequency = 27 mhz ; desired sampling rate, fs = 7.2 khz step 1. first compute the required vco frequency, fvco, corresponding to fs = 2.4 khz x 3 = 7.2 khz . fvco = 2 x 2304 x fs = 2 x 2304 x 2.4 khz x 3 = 33. 1776 mhz . step 2. express the required vco frequency divided by the crystal frequency as a ratio of two intege rs. this is initially given by : mhz fxtal fvco 27 3 2.4khz 2304 2 / ? ? ? = . after a few rounds of simplification this reduces to: 96 5 125 8 dnco2 nnco2 dnco1 nnco1 ) 5 96 ( ) 125 8 ( / = = ? = fxtal fvco the t wo ratios are not unique and many other possibilities exist. but for this particular application, they are found to be the best set of choices within the constraints of prst and nrst allowed. (nnco1, nnco2 must be less than or equal to 8.) the ratio, nn co1/dnco1 = 8/125, is used to form a divide ratio for the nco in prescaler and nnco2/dnco 2 =5/96 for the nco in the pll. pre - scaler nco: from nnco1/dnco1 = 8/125, pdvsr = integer [ dnco1/nnco1 ] = 15; prst[2:0] = nnco1 ? 1 = 7; dnco1/nnco1 = 125/8 = 15. 625 suggests a divide sequence of { 16, 16, 15, 16, 16, 15, 16, 15}, or pseq = {1,1,0,1,1,0,1,0} = dah. pll nco: from nnco2/dnco2 = 5/96, ndvsr = integer [ dnco2/nnco2 ] = 19; nrst[2:0] = nnco2 ? 1 = 4; dnco2/nnco2 = 19.2 suggests a divide sequence of { 19, 19, 19, 19, 20}, or nseq = {x,x,x,0,0,0,0,1} = x1h.
ds_1903_032 73m1903 data sheet rev. 2.1 47 revision history rev. # date comments 1.0 4/16/2004 first publication . 1.1 12/13/2004 minor format modification . 1.2 7/15/2005 company logo c hange and minor format modification . 1.4 9/14/2006 c orrected qfn pin - out drawing. 1.5 5/23/2007 added 20 - vt package information. 1.6 12/14/2007 changed 32 - qfn from punched to sawn. removed the leaded package option. 1.7 1/17/2008 changed the bottom view package dimension for 32 - qfn package . 2.0 2/23 /200 9 removed all references to the 32 - pin tqfp package . formatted to the new corporate standard. 2.1 3/9 /2010 added the schematic and bill of mate r i al s in section 10 . formatted to the new corporate standard. ? 2010 teridian semiconductor corporation. all rights reserved. teridian semiconductor corporation is a registered trademark of ter idian semiconductor corporation. simplifying system integration is a trademark of teridian semiconductor corporation. microdaa is a registered trademark of teridian semiconductor corporation. all other trademarks are the property of their respective owners . teridian semiconductor corporation makes no warranty for the use of its products, other than expressly contained in the company?s warranty detailed in the teridian semiconductor corporation standard terms and conditions. the company assumes no responsi bility for any errors which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice and does not make any commitment to update the information contained herein. accordingly, the reader is cautioned to verify that this document is current by comparing it to the latest version on http://www.teridian.com or by checking with your sales representative. teridian semiconductor corp., 6440 oak canyon, suite 100, irvine, ca 92618 tel (714) 508 - 8800, fax (714) 508 - 8877, http://www.teridian.com

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