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4 ADC with PLL, 192 kHz, 24-Bit Codec AD1974
FEATURES
Phase-locked loop generated or direct master clock Low EMI design 107 dB dynamic range and SNR -94 dB THD + N Single 3.3 V supply Tolerance for 5 V logic inputs Supports 24 bits and 8 kHz to 192 kHz sample rates Differential ADC input Log volume control with autoramp function SPI(R)-controllable for flexibility Software-controllable clickless mute Software power-down Right justified, left justified, I2S, and TDM modes Master and slave modes up to 16-channel input/output Available in a 48-lead LQFP
GENERAL DESCRIPTION
The AD1974 is a high performance, single-chip codec that provides four analog-to-digital converters (ADCs) with differential inputs using the Analog Devices, Inc. patented multibit sigmadelta (-) architecture. An SPI port is included, allowing a microcontroller to adjust volume and many other parameters. The AD1974 operates from 3.3 V digital and analog supplies. The AD1974 is available in a single-ended output 48-lead LQFP. The AD1974 is designed for low EMI. This consideration is apparent in both the system and circuit design architectures. By using the on-board phase-locked loop (PLL) to derive the master clock from the LR clock or from an external crystal, the AD1974 eliminates the need for a separate high frequency master clock and can also be used with a suppressed bit clock. The ADCs are designed using the latest continuous time architectures from Analog Devices to further minimize EMI. By using 3.3 V supplies, power consumption is minimized, further reducing emissions.
APPLICATIONS
Automotive audio systems Home Theater Systems Set-top boxes Digital audio effects processors
FUNCTIONAL BLOCK DIAGRAM
DIGITAL AUDIO INPUT/OUTPUT
AD1974
SERIAL DATA PORT
ADC ANALOG AUDIO INPUTS ADC ADC ADC
QUAD DEC FILTER 48kHz/ 96kHz/192kHz
SDATA OUT CLOCKS TIMING MANAGEMENT AND CONTROL (CLOCK AND PLL)
PRECISION VOLTAGE REFERENCE
CONTROL PORT SPI 12.48MHz
06614-001
CONTROL DATA INPUT/OUTPUT
Figure 1.
Rev. 0
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AD1974 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Test Conditions............................................................................. 3 Analog Performance Specifications ........................................... 3 Crystal Oscillator Specifications................................................. 4 Digital Input/Output Specifications........................................... 4 Power Supply Specifications........................................................ 5 Digital Filters................................................................................. 5 Timing Specifications .................................................................. 5 Absolute Maximum Ratings............................................................ 7 Thermal Resistance ...................................................................... 7 ESD Caution.................................................................................. 7 Pin Configuration and Function Descriptions............................. 8 Typical Performance Characteristics ........................................... 10 Theory of Operation ...................................................................... 11 Analog-to-Digital Converters (ADCs).................................... 11 Clock Signals............................................................................... 11 Reset and Power-Down ............................................................. 11 Serial Control Port ..................................................................... 12 Power Supply and Voltage Reference....................................... 12 Serial Data Ports--Data Format............................................... 12 TDM Modes................................................................................ 13 Daisy-Chain Mode ..................................................................... 15 Control Registers ............................................................................ 18 PLL and Clock Control Registers............................................. 18 AUXPORT Control Registers ................................................... 19 ADC Control Registers.............................................................. 20 Additional Modes....................................................................... 22 Application Circuits ....................................................................... 23 Outline Dimensions ....................................................................... 24 Ordering Guide............................................................................... 24
REVISION HISTORY
4/07--Revision 0: Initial Version
Rev. 0 | Page 2 of 24
AD1974 SPECIFICATIONS
TEST CONDITIONS
Performance of all channels is identical, exclusive of the interchannel gain mismatch and interchannel phase deviation specifications. Supply Voltages (AVDD, DVDD) Temperature Range 1 Master Clock Input Sample Rate Measurement Bandwidth Word Width Load Capacitance (Digital Output) Load Current (Digital Output) Input Voltage High Input Voltage Low
1
3.3 V As specified in Table 1 and Table 2 12.288 MHz (48 kHz fS, 256 x fS mode) 48 kHz 20 Hz to 20 kHz 24 bits 20 pF 1 mA or 1.5 k to 1/2 DVDD supply 2.0 V 0.8 V
Functionally guaranteed at -40C to +125C case temperature.
ANALOG PERFORMANCE SPECIFICATIONS
Specifications guaranteed at 25C (ambient). Table 1.
Parameter ANALOG-TO-DIGITAL CONVERTERS ADC Resolution Full-Scale Input Voltage (Differential) Dynamic Range No Filter (RMS) With A-Weighted Filter (RMS) Total Harmonic Distortion + Noise (THD + N) Gain Error Interchannel Gain Mismatch Offset Error Gain Drift Interchannel Isolation CMRR Input Resistance Input Capacitance Input Common-Mode Bias Voltage REFERENCE Internal Reference Voltage External Reference Voltage Common-Mode Reference Output Conditions All ADCs 20 Hz to 20 kHz, -60 dB input 98 100 -1 dBFS -10 -0.25 -10 102 105 -96 dB dB dB % dB mV ppm/C dB dB dB k pF V V V V Min Typ 24 1.9 Max Unit Bits V rms
100 mV rms, 1 kHz 100 mV rms, 20 kHz
0 100 -110 55 55 14 10 1.5 1.50 1.50 1.50
-87 +10 +0.25 +10
FILTR pin FILTR pin CM pin
1.32
1.68
Rev. 0 | Page 3 of 24
AD1974
Specifications measured at 130C (case). Table 2.
Parameter ANALOG-TO-DIGITAL CONVERTERS ADC Resolution Full-Scale Input Voltage (Differential) Dynamic Range No Filter (RMS) With A-Weighted Filter (RMS) Total Harmonic Distortion + Noise (THD + N) Gain Error Interchannel Gain Mismatch Offset Error REFERENCE Internal Reference Voltage External Reference Voltage Common-Mode Reference Output Conditions All ADCs 20 Hz to 20 kHz, -60 dB input 95 97 -1 dBFS -10 -0.25 -10 FILTR pin FILTR pin CM pin 102 105 -96 dB dB dB % dB mV V V V Min Typ 24 1.9 Max Unit Bits V rms
0 1.50 1.50 1.50
-87 +10 +0.25 +10
1.32
1.68
CRYSTAL OSCILLATOR SPECIFICATIONS
Table 3.
Parameter Transconductance Min Typ 3.5 Max Unit Mmhos
DIGITAL INPUT/OUTPUT SPECIFICATIONS
-40C < TA < +130C, DVDD = 3.3 V 10%. Table 4.
Parameter Input Voltage High (VIH) Input Voltage High (VIH) Input Voltage Low (VIL) Input Leakage High Level Output Voltage (VOH) Low Level Output Voltage (VOL) Input Capacitance Conditions/Comments MCLKI pin IIH @ VIH = 2.4 V IIL @ VIL = 0.8 V IOH = 1 mA IOL = 1 mA Min 2.0 2.2 Typ Max Unit V V V A A V V pF
0.8 10 10 DVDD - 0.60 0.4 5
Rev. 0 | Page 4 of 24
AD1974
POWER SUPPLY SPECIFICATIONS
Table 5.
Parameter SUPPLIES Voltage Conditions/Comments Min Typ Max Unit
Digital Current Normal Operation
Power-Down Analog Current Normal Operation Power-Down DISSIPATION Operation All Supplies Digital Supply Analog Supply Power-Down, All Supplies POWER SUPPLY REJECTION RATIO Signal at Analog Supply Pins
DVDD AVDD MCLK = 256 fS fS = 48 kHz fS = 96 kHz fS = 192 kHz fS = 48 kHz to 192 kHz
3.0 3.0
3.3 3.3 56 65 95 2.0 74 23
3.6 3.6
V V mA mA mA mA mA mA
MCLK = 256 fS, 48 kHz 429 185 244 83 1 kHz, 200 mV p-p 20 kHz, 200 mV p-p 50 50 mW mW mW mW dB dB
DIGITAL FILTERS
Table 6.
Parameter ADC DECIMATION FILTER Pass Band Pass-Band Ripple Transition Band Stop Band Stop-Band Attenuation Group Delay Mode All modes @ 48 kHz Factor 0.4375 fS 0.5 fS 0.5625 fS 79 22.9844 fS 479 Min Typ 21 0.015 24 27 Max Unit kHz dB kHz kHz dB s
TIMING SPECIFICATIONS
-40C < TA < +130C, DVDD = 3.3 V 10%. Table 7.
Parameter INPUT MASTER CLOCK (MCLK) AND RESET tMH tMH fMCLK fMCLK tPDR tPDRR Condition Comments Min Max Unit
MCLK duty cycle
MCLK frequency Low Recovery
ADC clock source = PLL clock @ 256 fS, 384 fS, 512 fS, 768 fS ADC clock source = direct MCLK @ 512 fS (bypass on-chip PLL) PLL mode, 256 fS reference Direct 512 fS mode Reset to active output
40 40 6.9 15 4096
60 60 13.8 27.6
% % MHz MHz ns tMCLK
Rev. 0 | Page 5 of 24
AD1974
Parameter PLL Lock Time 256 fS VCO Clock Output Duty Cycle MCLK_O Pin SPI PORT tCCH tCCL fCCLK tCDS tCDH tCLS tCLH tCLHIGH tCOE tCOD tCOH tCOTS ADC SERIAL PORT tABH tABL tALS tALH tALS tABDD AUXILIARY INTERFACE tXDS tXDH tXBH tXBL tXLS tXLH Condition MCLK and LRCLK input 40 Comments Min Max 10 60 Unit ms %
See Figure 5 CCLK high CCLK low CCLK frequency CDATA setup CDATA hold Setup Hold High COUT enable COUT delay COUT hold COUT tristate ABCLK high ABCLK low ALRCLK setup ALRCLK hold ALRCLK skew ASDATA delay AAUXDATA setup AAUXDATA hold AUXBCLK high AUXBCLK low AUXLRCLK setup AUXLRCLK hold 35 35 fCCLK = 1/tCCP; only tCCP shown in Figure 5 To CCLK rising From CCLK rising To CCLK rising From CCLK falling Not shown in Figure 5 From CCLK falling From CCLK falling From CCLK falling, not shown in Figure 5 From CCLK falling See Figure 13 Slave mode Slave mode To ABCLK rising, slave mode From ABCLK rising, slave mode From ABCLK falling, master mode From ABCLK falling See Figure 12 To AUXBCLK rising From AUXBCLK rising 10 10 10 10 10 30 30 30 30 10 10 10 5 -8 10 ns ns MHz ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
+8 18
To AUXBCLK rising From AUXBCLK rising
10 5 10 10 10 5
Rev. 0 | Page 6 of 24
AD1974 ABSOLUTE MAXIMUM RATINGS
Table 8.
Parameter Analog (AVDD) Digital (DVDD) Input Current (Except Supply Pins) Analog Input Voltage (Signal Pins) Digital Input Voltage (Signal Pins) Operating Temperature Range (Case) Storage Temperature Range Rating -0.3 V to +3.6 V -0.3 V to +3.6 V 20 mA -0.3 V to AVDD + 0.3 V -0.3 V to DVDD + 0.3 V -40C to +125C -65C to +150C
THERMAL RESISTANCE
JA represents thermal resistance, junction-to-ambient; JC represents the thermal resistance, junction-to-case. All characteristics are for a 4-layer board. Table 9.
Package Type 48-Lead LQFP JA 50.1 JC 17 Unit C/W
ESD CAUTION
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Rev. 0 | Page 7 of 24
AD1974 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
ADC2RN ADC1RN ADC2RP ADC1RP ADC2LN ADC1LN ADC2LP ADC1LP AVDD
48 47 46 45 44 43 42 41 40 39 38 37
AGND MCLKI/XI MCLKO/XO AGND AVDD NC NC NC NC
AVDD
CM
LF
1 2 3 4 5 6 7 8 9
36 35 34 33
AGND FILTR AGND AVDD AGND NC NC NC NC CLATCH CCLK DGND
AD1974
TOP VIEW (Not to Scale) SINGLE-ENDED OUTPUT
32 31 30 29 28 27 26 25
PD/RST 10 NC 11 DGND 12
13 14 15 16 17 18 19 20 21 22 23 24
CIN
AUXLRCLK
AUXBCLK
ASDATA2
AUXDATA2
AUXDATA1
ASDATA1
ALRCLK
ABCLK
COUT
DVDD
NC
NC = NO CONNECT
Figure 2. AD1974 Single-Ended Output, 48-Lead LQFP Pin Configuration
Table 10. Pin Function Description
Pin No. 1, 4, 32, 34, 36 2 3 5, 33, 37, 48 6 to 9, 11, 16, 28 to 31 10 12, 25 13 14 15 17 18 19 20 21 22 23 24 26 27 35 38 39 40 41 42 43 Type1 I I O I I I I I/O I/O I/O I/O I/O O I/O I/O I I/O I I O O I I I I I Mnemonic AGND MCLKI/XI MCLKO/XO AVDD NC PD/RST DGND DVDD AUXDATA2 AUXDATA1 AUXBCLK AUXLRCLK ASDATA2 ASDATA1 ABCLK ALRCLK CIN COUT CCLK CLATCH FILTR CM ADC1LP ADC1LN ADC1RP ADC1RN ADC2LP Description Analog Ground. Master Clock Input/Crystal Oscillator Input. Master Clock Output/Crystal Oscillator Output. Analog Power Supply. Connect to analog 3.3 V supply. No Connect. Power-Down/Reset (Active Low). Digital Ground. Digital Power Supply. Connect to digital 3.3 V supply. Auxiliary Data Input 2 (From External ADC 2). Auxiliary Data Input 1 (From External ADC 1). Auxiliary Bit Clock. Auxiliary Left-Right Framing Clock. ADC Serial Data Output 2 (ADC 2 Left and ADC 2 Right)/ADC TDM Data Input. ADC Serial Data Output 1 (ADC 1 Left and ADC 1 Right)/ADC TDM Data Output. Serial Bit Clock for ADCs. Left-Right Framing Clock for ADCs. Control Data Input (SPI). Control Data Output (SPI). Control Clock Input (SPI). Latch Input for Control Data (SPI). Voltage Reference Filter Capacitor Connection. Bypass with 10 F||100 nF to AGND. Common-Mode Reference Filter Capacitor Connection. Bypass with 47 F||100 nF to AGND. ADC1 Left Positive Input. ADC1 Left Negative Input. ADC1 Right Positive Input. ADC1 Right Negative Input. ADC2 Left Positive Input.
Rev. 0 | Page 8 of 24
06614-020
AD1974
Pin No. 44 45 46 47
1
Type1 I I I O
Mnemonic ADC2LN ADC2RP ADC2RN LF
Description ADC2 Left Negative Input. ADC2 Right Positive Input. ADC2 Right Negative Input. PLL Loop Filter, Return to AVDD.
I = input, O = output.
Rev. 0 | Page 9 of 24
AD1974 TYPICAL PERFORMANCE CHARACTERISTICS
0.10 0.08 0.06
MAGNITUDE (dB)
0 -10 -20 -30 -40 -50 -60 -70 -80 -90
06614-002
0.04
MAGNITUDE (dB)
0.02 0 -0.02 -0.04 -0.06 -0.08 -0.10 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 FREQUENCY (kHz)
0
5000 10000 15000 20000 25000 30000 35000 40000 FREQUENCY (kHz)
Figure 3. ADC Pass-Band Filter Response, 48 kHz
Figure 4. ADC Stop-Band Filter Response, 48 kHz
Rev. 0 | Page 10 of 24
06614-003
-100
AD1974 THEORY OF OPERATION
ANALOG-TO-DIGITAL CONVERTERS (ADCS)
There are four ADC channels in the AD1974 configured as two stereo pairs with differential inputs. The ADCs can operate at a nominal sample rate of 48 kHz, 96 kHz, or 192 kHz. The ADCs include on-board digital antialiasing filters with a 79 dB stopband attenuation and a linear phase response, operating at an oversampling ratio of 128 (48 kHz, 96 kHz, and 192 kHz modes). Digital outputs are supplied through two serial data output pins (one for each stereo pair) as well as a common frame (ALRCLK) and bit clock (ABCLK). Alternatively, one of the time division multiplexed (TDM) modes can be used to access up to 16 channels on a single TDM data line. The ADCs must be driven from a differential signal source for best performance. The input pins of the ADCs connect to internal switched capacitors. To isolate the external driving op amp from the glitches caused by the internal switched capacitors, each input pin should be isolated by using a series connected, external, 100 resistor together with a 1 nF capacitor connected from each input to ground. This capacitor must be of high quality, for instance, a ceramic NPO capacitor or a polypropylene film capacitor. The differential inputs have a nominal common-mode voltage of 1.5 V. The voltage at the common-mode reference pin (CM) can be used to bias external op amps to buffer the input signals (see the Power Supply and Voltage Reference section). The inputs can also be ac-coupled and do not need an external dc bias to CM. A digital high-pass filter can be switched in line with the ADCs under serial control to remove residual dc offsets. It has a 1.4 Hz, 6 dB per octave cutoff at a 48 kHz sample rate. The cutoff frequency scales directly with sample frequency. The voltage at CM can be used to bias the external op amps that buffer the output signals (see the Power Supply and Voltage Reference section). The internal clock for the ADCs is 256 x fS for all clock modes. By default, the on-board PLL generates this internal master clock from an external clock. A direct 512 x fS (referenced to 48 kHz mode) master clock can be used for the ADCs if selected in the PLL and Clock Control 1 register. Note that it is not possible to use a direct clock for the ADCs set to the 192 kHz mode. It is required that the on-chip PLL be used in this mode. The PLL can be powered down in the PLL and Clock Control 0 register. To ensure reliable locking when changing PLL modes, or if the reference clock is unstable at power-on, power down the PLL and then power it back up when the reference clock has stabilized. The internal MCLK can be disabled in the PLL and Clock Control 0 register to reduce power dissipation when the AD1974 is idle. The clock should be stable before it is enabled. Unless a standalone mode is selected (see the Serial Control Port section), the clock is disabled by reset and must be enabled by writing to the SPI or I2C port for normal operation. To maintain the highest performance possible, it is recommended that the clock jitter of the internal master clock signal be limited to less than 300 ps rms time interval error (TIE). Even at these levels, extra noise or tones can appear in the outputs if the jitter spectrum contains large spectral peaks. If the internal PLL is not being used, it is highly recommended that an independent crystal oscillator generate the master clock. In addition, it is especially important that the clock signal should not be passed through an FPGA, CPLD, DSP, or other large digital chip before being applied to the AD1974. In most cases, this induces clock jitter due to the sharing of common power and ground connections with other unrelated digital output signals. When the PLL is used, jitter in the reference clock is attenuated above a certain frequency depending on the loop filter.
CLOCK SIGNALS
The on-chip PLL can be selected to reference the input sample rate from either the LRCLK or AUXLRCK pins or 256, 384, 512, or 768 times the sample rate, referenced to the 48 kHz mode from the MCLKI/XI pin. The default at power-up is 256 x fS from MCLKI. In 96 kHz mode, the master clock frequency stays at the same absolute frequency; therefore, the actual multiplication rate is divided by 2. In 192 kHz mode, the actual multiplication rate is divided by 4. For example, if the AD1974 is programmed in 256 x fS mode, the frequency of the master clock input is 256 x 48 kHz = 12.288 MHz. If the AD1974 is then switched to 96 kHz operation (by writing to the SPI or I2C port), the frequency of the master clock should remain at 12.288 MHz (128 x fS). In 192 kHz mode, this becomes 64 x fS.
RESET AND POWER-DOWN
The reset pin sets all the control registers to their default settings. To avoid pops, reset does not power down the analog outputs. After reset is deasserted, and the PLL acquires a lock condition, an initialization routine runs inside the AD1974. This initialization lasts for approximately 256 master clock cycles. The PLL and Clock Control 0 register and the ADC Control 1 register power down their respective sections using power down bits. All other register settings are retained. The PD/RST pin should be pulled low by an external resistor to guarantee proper startup.
Rev. 0 | Page 11 of 24
AD1974
Table 11. Standalone Mode Selection
ADC Clocks Slave Master
tCLS
CLATCH
CIN 0 0
COUT 0 1
CCLK 0 0
CLATCH 0 0
tCLH tCOTS
tCCP
tCCH tCCL
CCLK
tCDS tCDH
CIN D23 D22 D9 D8 D0
COUT
tCOE tCOD
D9
D8
D0
06614-010
Figure 5. Format of the SPI Signal
SERIAL CONTROL PORT
The AD1974 has an SPI control port that permits the programming and reading back of the internal control registers for the ADCs and the clock system. There is also a standalone mode available for operation without serial control that is configured at reset using the serial control pins. All registers are set to default, except the internal MCLK enable, which is set to 1; ADC BCLK and LRCLK master/slave, which are set by COUT. Standalone mode only supports stereo mode with an I2S data format and 256 fS MCLK rate (see Table 11 for details). Using a weak pull-up resistor in applications that have a microcontroller is highly recommended. This pull-up resistor ensures that the AD1974 recognizes the presence of a microcontroller. The SPI control port of the AD1974 is a 4-wire serial control port. The format is similar to that of the Motorola SPI(R) format except that the input data-word is 24 bits wide. The serial bit clock and latch can be completely asynchronous to the sample rate of the ADCs. Figure 5 shows the format of the SPI signal. The first byte is a global address with a read/write bit. For the AD1974, the address is 0x04, shifted left one bit due to the R/W bit. The second byte is the AD1974 register address and the third byte is the data.
means of a ferrite bead in series with each supply. It is important that the analog supply be as clean as possible. All digital inputs are compatible with TTL and CMOS levels. All outputs are driven from the 3.3 V DVDD supply and are compatible with TTL and 3.3 V CMOS levels. The ADC internal voltage reference (VREF) is brought out on FILTR and should be bypassed as close as possible to the AD1974 with a parallel combination of 10 F and 100 nF. Any external current drawn should be limited to less than 50 A. VREF can be disabled in the PLL and Clock Control 1 register and FILTR can be driven from an external source. The ADC input gain varies by the inverse ratio. CM is the internal common-mode reference. It should be bypassed as close as possible to the AD1974, with a parallel combination of 47 F and 100 nF. This voltage can be used to bias external op amps to the common-mode voltage of the input and output signal pins. The output current should be limited to less than 0.5 mA source and 2 mA sink.
SERIAL DATA PORTS--DATA FORMAT
The four ADC channels use a common serial bit clock (ABCLK) and a left-right framing clock (ALRCLK) in the serial data port. The clock signals are all synchronous with the sample rate. The normal stereo serial modes are shown in Figure 11. The ADC serial data modes default to I2S. The ports can also be programmed for left justified, right justified, and TDM modes. The word width is 24 bits by default and can be programmed for 16 or 20 bits. The ADC serial formats and serial clock polarity are programmable according to the ADC Control 1 register. The ADC serial ports are programmable to become the bus masters according to the ADC Control 2 register. By default, both ADC serial ports are in the slave mode.
POWER SUPPLY AND VOLTAGE REFERENCE
The AD1974 is designed for 3.3 V supplies. Separate power supply pins (Pin 5, Pin 13, Pin 33, Pin 37, and Pin 38) are provided for the analog and digital sections. These pins should be bypassed with 100 nF ceramic chip capacitors, as close to the pins as possible, to minimize noise pickup. A bulk aluminum electrolytic capacitor of at least 22 F should also be placed on the same PC board as the codec. For critical applications, improved performance is obtained with separate supplies for the analog and digital sections. If this is not possible, it is recommended that the analog and digital supplies be isolated by
Rev. 0 | Page 12 of 24
AD1974
TDM MODES
The AD1974 serial ports also have several different TDM serial data modes. The first and most commonly used configuration is shown in Figure 6 where the ADC serial port outputs one data stream consisting of four on-chip ADCs followed by four unused slots. In this mode, ABCLK is set to 256 fS (8-channel TDM mode). The I/O pins of the serial ports are defined according to the serial mode selected. For a detailed description of the function of each pin in TDM and AUX Modes, see Table 12.
MSB MSB-1 MSB-2
put stream follow four on-chip ADC channel slots. It should be noted that due to the high ABCLK frequency, this mode is available only in the 48 kHz/44.1 kHz/32 kHz sample rate.
ALRCLK 256 BCLKs ABCLK 32 BCLKs ADATA SLOT 1 LEFT 1 SLOT 2 RIGHT 1 SLOT 3 LEFT 2 SLOT 4 RIGHT 2 UNUSED UNUSED UNUSED UNUSED
ALRCLK ABCLK ADATA
06614-016
The AD1974 allows system configurations with more than four ADC channels (see Figure 7 and Figure 8) that use 8 ADCs and 16 ADCs. In this mode, four AUX channel slots in the TDM outTable 12. Pin Function Changes in TDM and AUX Modes
Pin Name ASDATA1 ASDATA2 AUXDATA1 AUXDATA2 ALRCLK ABCLK AUXLRCLK AUXBCLK Stereo Mode ADC1 data output ADC2 data output Not used (ground) Not used (ground) ADC LRCLK input/output ADC BCLK input/output Not used (ground) Not used (ground)
Figure 6. ADC TDM (8-Channel I2S Mode.
TDM Mode ADC TDM data output ADC TDM data input Not used (ground) Not used (ground) ADC TDM frame sync input/output ADC TDM BCLK input/output Not used (ground) Not used (ground)
AUX Mode ADCTDM data output Not used (float) AUXDATA in 1 (from external ADC1) AUXDATA in 2 (from external ADC2) ADCTDM frame sync input/output ADCTDM BCLK input/output AUXLRCLK input/output AUXBCLK input/output
ALRCLK
ABCLK FOUR-ON-CHIP DAC CHANNELS ASDATA1 (TDM_OUT) ADCL1 ADCR1 ADCL2 ADCR2 AUXL1 FOUR-AUX ADC CHANNELS AUXR1 AUXL2 AUXR2
32 BITS
MSB
AUXLRCLK (AUX PORT) AUXBCLK (AUX PORT) AUXDATA1 (AUX1_IN) AUXDATA2 (AUX2_IN)
LEFT
RIGHT
MSB
MSB
06614-050
MSB
MSB
Figure 7. 8-Channel AUX ADC Mode
Rev. 0 | Page 13 of 24
AD1974
ALRCLK ABCLK
ASDATA1 (TDM_OUT)
FOUR-ON-CHIP ADC CHANNELS
ADCL1 ADCR1 ADCL2 ADCR2
AUXILIARY ADC CHANNELS
AUXL1 AUXR1 AUXL2
UNUSED SLOTS
AUXR2 UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED
32 BITS
MSB
AUXLRCLK (AUX PORT) AUXBCLK (AUX PORT) AUXDATA1 (AUX1_IN) AUXDATA2 (AUX2_IN)
LEFT
RIGHT
MSB
MSB
06614-052
MSB
MSB
Figure 8. 16-Channel AUX ADC Mode
Rev. 0 | Page 14 of 24
AD1974
DAISY-CHAIN MODE
The AD1974 also allows a daisy-chain configuration to expand the system to 8 ADCs and 16 ADCs (see Figure 9 and Figure 10). There are two configurations for the ADC port to work in daisy-chain mode. The first one is with an ABCLK at 256 fS shown in Figure 9. The second configuration is with an ABCLK at 512 fS shown in Figure 10. Note that in the 512 fS ABCLK mode, the ADC channels occupy the first eight slots, the second eight slots are empty. The TDM_IN of the first AD1974 must be grounded in all modes of operation. The second AD1974 is the device attached to the DSP TDM port.
ALRCLK
The I/O pins of the serial ports are defined according to the serial mode selected. See Table 13 for a detailed description of the function of each pin. See Figure 14 for a typical AD1974 configuration with two external stereo ADCs. Figure 11 through Figure 13 show the serial mode formats. For maximum flexibility, the polarity of LRCLK and BCLK are programmable. All of the clocks are shown with their normal polarity. The default mode is I2S.
ABCLK FOUR ADC CHANNELS OF THE SECOND IC IN THE CHAIN ADCL1 ADCR1 ADCL2 ADCR2 FOUR ADC CHANNELS OF THE FIRST IC IN THE CHAIN ADCL1 ADCR1 ADCL2 ADCR2
ASDATA1 (TDM_OUT OF THE SECOND AD1974 IN THE CHAIN) ASDATA2 (TDM_IN OF THE SECOND AD1974 IN THE CHAIN)
ADCL1
ADCR1
ADCL2
ADCR2
32 BITS FIRST AD1974 SECOND AD1974 DSP
06614-056 06614-057
MSB
Figure 9. ADC TDM Daisy-Chain Mode (256 fS ABCLK, Two AD1974 Daisy Chains)
ALRCLK
ABCLK
ASDATA1 (TDM_OUT OF THE SECOND AD1974 IN THE CHAIN)
FOUR ADC CHANNELS OF THE SECOND IC IN THE CHAIN
ADCL1 ADCR1 ADCL2 ADCR2
FOUR ADC CHANNELS OF THE FIRST IC IN THE CHAIN
ADCL1 ADCR1 ADCL2 ADCR2 UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED
ASDATA2 (TDM_IN OF THE SECOND AD1974 IN THE CHAIN)
ADCL1
ADCR1
ADCL2
ADCR2 UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED
32 BITS
FIRST AD1974
SECOND AD1974
DSP
MSB
Figure 10. ADC TDM Daisy-Chain Mode (512 fS ABCLK, Two AD1974 Daisy Chains)
Rev. 0 | Page 15 of 24
AD1974
ALRCLK ABCLK ASDATA MSB LSB MSB LSB LEFT CHANNEL RIGHT CHANNEL
LEFT JUSTIFIED MODE--16 BITS TO 24 BITS PER CHANNEL
ALRCLK ABCLK ASDATA MSB
LEFT CHANNEL
RIGHT CHANNEL
LSB
MSB
LSB
I2S MODE--16 BITS TO 24 BITS PER CHANNEL
ALRCLK ABCLK ASDATA
LEFT CHANNEL
RIGHT CHANNEL
MSB
LSB
MSB
LSB
RIGHT JUSTIFIED MODE--SELECT NUMBER OF BITS PER CHANNEL ALRCLK ABCLK ASDATA MSB LSB MSB LSB
DSP MODE--16 BITS TO 24 BITS PER CHANNEL 1/fS
06614-013
NOTES 1. DSP MODE DOES NOT IDENTIFY CHANNEL. 2. LRCLK NORMALLY OPERATES AT fS EXCEPT FOR DSP MODE WHICH IS 2 x fS. 3. BCLK FREQUENCY IS NORMALLY 64 x LRCLK BUT MAY BE OPERATED IN BURST MODE.
Figure 11. Stereo Serial Modes
tXBH
AUXBCLK
tXBL tXLS
AUXRCLK
tXLH
tXDS
AUXDATA LEFT JUSTIFIED MODE
MSB
MSB-1
tXDH
AUXDATA
tXDS
MSB
I2C JUSTIFIED MODE
tXDH tXDS
AUXDATA RIGHT JUSTIFIED MODE
tXDS
06614-014
MSB
LSB
tXDH
tXDH
Figure 12. Auxiliary Serial Timing
Rev. 0 | Page 16 of 24
AD1974
tABH
ABCLK
tABL tALS
ALRCLK
tALH
tABDD
ASDATA LEFT JUSTIFIED MODE MSB MSB-1
tABDD
ASDATA I2C JUSTIFIED MODE MSB
tABDD
LSB
06614-015
ASDATA RIGHT JUSTIFIED MODE
MSB
Figure 13. ADC Serial Timing
Table 13. Pin Function Changes in TDM and AUX Modes (Replication of Table 12)
Pin Name ASDATA1 ASDATA2 AUXDATA1 AUXDATA2 ALRCLK ABCLK AUXLRCLK AUXBCLK Stereo Mode ADC1 data output ADC2 data output Not used (ground) Not used (ground) ADC LRCLK input/output ADC BCLK input/output Not used (ground) Not used (ground) TDM Mode ADC TDM data output ADC TDM data input Not used (ground) Not used (ground) ADC TDM Frame Sync input/output ADC TDM BCLK input/output Not used (ground) Not used (ground) AUX Mode ADCTDM data output Not used (float) AUXDATA in 1 (from external ADC1) AUXDATA in 2 (from external ADC2) ADCTDM frame sync input/output ADCTDM BCLK input/output AUXLRCLK input/output AUXBCLK input/output
30MHz
FSYNC-TDM (RFS)
SHARC
SHARC IS RUNNING IN SLAVE MODE (INTERRUPT-DRIVEN)
RxDATA
RxCLK
LRCLK AUX ADC 1 BCLK DATA MCLK ASDATA1 ALRCLK ABCLK AUXBCLK AUXLRCLK LRCLK AUX ADC 2 BCLK DATA MCLK AUXDATA1 AUXDATA2 MCLK
AD1974
TDM MASTER AUX MASTER
06614-019
Figure 14. Example of AUX Mode Connection to SHARC(R) (AD1974 as TDM Master/AUX Master Shown)
Rev. 0 | Page 17 of 24
TxCLK
12.288MHz
TFS (NC)
AD1974 CONTROL REGISTERS
The format is the same for I2C and SPI ports. The global address for the AD1974 is 0x04, shifted left one bit due to the R/W bit. All registers are reset to 0. Note that the first setting in each control register parameter is the default setting. Table 14. Register Format
Global Address Bit 23:17 R/W 16 Register Address 15:8 Data 7:0
Table 15. Register Addresses Description
Address 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Function PLL and Clock Control 0 PLL and Clock Control 1 AUXPORT Control 0 AUXPORT Control 1 AUXPORT Control 2 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved ADC Control 0 ADC Control 1 ADC Control 2
PLL AND CLOCK CONTROL REGISTERS
Table 16. PLL and Clock Control 0
Bit 0 2:1 Value 0 1 00 01 10 11 00 01 10 11 00 01 10 11 0 1 Function Normal operation Power-down INPUT 256 (x44.1 kHz or 48 kHz) INPUT 384 (x44.1 kHz or 48 kHz) INPUT 512 (x44.1 kHz or 48 kHz) INPUT 768 (x44.1 kHz or 48 kHz) XTAL oscillator enabled 256 x fS VCO output 512 x fS VCO output Off MCLKI/XI AUXLRCLK ALRCLK Reserved Disable: ADC idle Enable: ADC active Description PLL power-down MCLKI/XI pin functionality (PLL active), master clock rate setting
4:3
MCLKO/XO pin, master clock rate setting
6:5
PLL input
7
Internal MCLK enable
Rev. 0 | Page 18 of 24
AD1974
Table 17. PLL and Clock Control 1
Bit 0 1 2 3 7:4 Value 0 1 0 1 0 1 0 1 0000 Function PLL clock MCLK PLL clock MCLK Enabled Disabled Not locked Locked Reserved Description AUXPORT clock source select ADC clock source select On-chip voltage reference PLL lock indicator (read only)
AUXPORT CONTROL REGISTERS
Table 18. AUXPORT Control 0
Bit 0 2:1 Value 0 1 00 01 10 11 000 001 010 011 100 101 110 111 00 01 10 11 Function Reserved Reserved 32 kHz/44.1 kHz/48 kHz 64 kHz/88.2 kHz/96 kHz 128 kHz/176.4 kHz/192 kHz Reserved 1 0 8 12 16 Reserved Reserved Reserved Stereo (normal) Reserved ADC AUX mode (ADC-, TDM-coupled) Reserved Description Reserved Sample rate
5:3
AUXDATA delay (AUXBCLK periods)
7:6
Serial format
Table 19. AUXPORT Control 1
Bit 0 2:1 Value 0 1 00 01 10 11 0 1 0 1 0 1 0 1 0 1 Function Reserved Reserved 64 (two channels) Reserved Reserved Reserved Left low Left high Slave Master Slave Master AUXBCLK pin Internally generated Normal Inverted Description
AUXBCLKs per frame
3 4 5 6 7
AUXLRCLK polarity AUXLRCLK master/slave AUXBCLK master/slave AUXBCLK source AUXBCLK polarity
Rev. 0 | Page 19 of 24
AD1974
Table 20. AUXPORT Control 2
Bit 0 2:1 Value 0 1 00 01 10 11 00 01 10 11 0 1 00 Function Reserved Reserved Reserved Reserved Reserved Reserved 24 20 Reserved 16 Reserved Reserved Reserved Description
4:3
Word width
5 7:6
ADC CONTROL REGISTERS
Table 21. ADC Control 0
Bit 0 1 2 3 4 5 7:6 Value 0 1 0 1 0 1 0 1 0 1 0 1 00 01 10 11 Function Normal Power down Off On Unmute Mute Unmute Mute Unmute Mute Unmute Mute 32 kHz/44.1 kHz/48 kHz 64 kHz/88.2 kHz/96 kHz 128 kHz/176.4 kHz/192 kHz Reserved Description Power-down High-pass filter ADC1L mute ADC1R mute ADC2L mute ADC2R mute Output sample rate
Table 22. ADC Control 1
Bit 1:0 Value 00 01 10 11 000 001 010 011 100 101 110 111 Function 24 20 Reserved 16 1 0 8 12 16 Reserved Reserved Reserved Description Word width
4:2
SDATA delay (BCLK periods)
Rev. 0 | Page 20 of 24
AD1974
Bit 6:5 Value 00 01 10 11 0 1 Function Stereo TDM (daisy chain) ADC AUX mode (TDM-coupled) Reserved Latch in midcycle (normal) Latch in at end of cycle (pipeline) Description Serial format
7
BCLK active edge (TDM_IN)
Table 23. ADC Control 2
Bit 0 1 2 3 5:4 Value 0 1 0 1 0 1 0 1 00 01 10 11 0 1 0 1 Function 50/50 (allows 32-/24-/20-/16-BCLK per channel) Pulse (32-BCLK/channel) Drive out on falling edge (DEF) Drive out on rising edge Left low Left high Slave Master 64 128 256 512 Slave Master ABCLK pin Internally generated Description LRCLK format BCLK polarity LRCLK polarity LRCLK master/slave BCLKs per frame
6 7
BCLK master/slave BCLK source
Rev. 0 | Page 21 of 24
AD1974
ADDITIONAL MODES
The AD1974 offers several additional modes for board level design enhancements. To reduce the EMI in board level design, serial data can be transmitted without an explicit BCLK. See Figure 15 for an example of an ADC TDM data transmission mode that does not require high speed ABCLK. This configuration is applicable when the AD1974 master clock is generated by the PLL with the ALRCLK as the PLL reference frequency. To relax the requirement for the setup time of the AD1974 in cases of high speed TDM data transmission, the AD1974 can latch in the data using the falling edge of ABCLK. This effectively dedicates the entire BCLK period to the setup time. This mode is useful in cases where the source has a large delay time in the serial data driver. Figure 16 shows this pipeline mode of data transmission.
ALRCLK 32 BITS INTERNAL ABCLK
ASDATA2
ALRCLK
INTERNAL ABCLK
06614-059
ASDATA2
Figure 15. Serial ADC Data Transmission in TDM Format Without ABCLK (Applicable Only If PLL Locks to ALRCLK)
ALRCLK
ABCLK DATA MUST BE VALID AT THIS BCLK EDGE
ASDATA1
MSB
Figure 16. I2S Pipeline Mode in ADC Serial Data Transmission (Applicable in Stereo and TDM Useful for High Frequency TDM Transmission)
Rev. 0 | Page 22 of 24
06614-060
AD1974 APPLICATION CIRCUITS
Typical applications circuits are shown in Figure 17 and Figure 18. Figure 17 shows a typical ADC input filter circuit. Recommended loop filters for LR clock and master clock as the PLL reference are shown in Figure 18.
120pF 600Z 100pF 5.76k 2 3 - OP275 + 5.76k 1
AUDIO INPUT
LF +
LRCLK 39nF 2.2nF 3.32k
LF
MCLK 5.6nF 390pF
06614-027
562 AVDD2
AVDD2
5.76k 120pF 4.7F 237 + 1nF NPO
ADCxN
Figure 18. Recommended Loop Filters for LRCLK or MCLK PLL Reference
100pF 6 5 5.76k - OP275 + 7 1nF NPO 4.7F 237 +
Figure 17. Typical ADC Input Filter Circuit
Rev. 0 | Page 23 of 24
06614-023
ADCxP
AD1974 OUTLINE DIMENSIONS
0.75 0.60 0.45 1.60 MAX
48 1
PIN 1
9.20 9.00 SQ 8.80
37 36
1.45 1.40 1.35
0.15 0.05
TOP VIEW
0.20 0.09 7 3.5 0 0.08 COPLANARITY
(PINS DOWN)
7.20 7.00 SQ 6.80
12 13 24
25
SEATING PLANE
VIEW A
COMPLIANT TO JEDEC STANDARDS MS-026-BBC
Figure 19. 48-Lead Low Profile Quad Flat Package [LQFP] (ST-48) Dimensions shown in millimeters
ORDERING GUIDE
Model AD1974YSTZ 1, 2 AD1974YSTZ-RL1, 2 EVAL-AD1974EB EVAL-AD1974EBZ1
1 2
Temperature Range -40C to +105C -40C to +105C
Package Description 48-Lead LQFP 48-Lead LQFP, 13" Reel Evaluation Board Evaluation Board
Z = RoHS Compliant Part. Single-ended output; SPI control port.
(c)2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06614-0-4/07(0)
Rev. 0 | Page 24 of 24
051706-A
ROTATED 90 CCW
VIEW A
0.50 BSC LEAD PITCH
0.27 0.22 0.17
Package Option ST-48 ST-48

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