ASM3P2853a peak emi reducing solution ?2010 scillc. all rights reserved. publication order number: february 2012 C rev. 3 ASM3P2853/d features generates an emi optimized clock signal at output. input frequency: 25mhz. frequency outputs: o usb clock (48mhz unmodulated) o 50mhz (modulated), 1% centre spread modulation rate: 39khz. spread spectrum on/off control supply voltage range 2.5v 5%. available in 8-pin soic package. product description the ASM3P2853a is a versatile spread spectrum frequency modulator. the ASM3P2853a reduces electromagnetic interference (emi) at the clock sou rce. the ASM3P2853a allows significant system cost savin gs by reducing the number of circuit board layers and shielding that are required to pass emi regulations . the ASM3P2853a modulates the output of pll in order to spread the bandwidth of a synthesized clock, thereb y decreasing the peak amplitudes of its harmonics. th is results in significantly lower system emi compared to the typical narrow band signal produced by oscillators and most clock generators. lowering emi by increasing a signals bandwidth is called spread spectrum clock generation. applications ASM3P2853a is targeted towards emi management for high speed digital applications such as pc peripher al devices, consumer electronics and embedded controll er systems. block diagram v ss v dd crystal oscillator 50mhz modulated xin xout usb clock (48mhz unmodulated) pll1 pll2 pwdnb ssonb
ASM3P2853a rev. 2 | page 2 of 7 | www.onsemi.com pin configuration pin description pin# pin name type description 1 xin i connection to crystal or external reference frequen cy input. this pin has dual functions. it can be connected either to an externa l crystal or an external reference clock. 2 xout o connection to crystal. if using an external referen ce clock, this pin must be left unconnected. 3 v dd p power supply for the analog and digital blocks. 4 v ss p ground to entire chip. 5 pwdnb i power-down control pin. pull low to enable the powe r-down mode. connect to vdd, if not used. 6 ssonb i digital logic input used to enable spread spectrum function (active low). spread spectrum is enabled when low, disabled when high. 7 usb clock o clock output-1 (48mhz unmodulated). 8 50mhz o clock output-2 (50mhz modulated). 50mhz v ss xout xin v dd 8 7 6 5 1 2 3 4 ASM3P2853a pwdnb ssonb usb clock
ASM3P2853a rev. 2 | page 3 of 7 | www.onsemi.com absolute maximum ratings symbol parameter rating unit vdd, v in voltage on any pin with respect to ground -0.5 to +4.6 v t stg storage temperature -65 to +125 c t s max. soldering temperature (10 sec) 260 c t j junction temperature 150 c t dv static discharge voltage (as per jedec std22- a114 -b) 2 kv note: these are stress ratings only and are not imp lied for functional use. exposure to absolute maxim um ratings for prolonged periods of time may affect device reliability. operating conditions parameter symbol condition / description min typ max unit supply voltage v dd 2.5v 5% 2.375 2.5 2.625 v ambient operating temperature range t a -40 - +85 c crystal resonator frequency f xin 25 mhz output driver load capacitance c l - - 15 pf crystal specifications fundamental at cut parallel resonant crystal nominal frequency 25mhz frequency tolerance 50ppm or better at 25c operating temperature range -25c to +85c storage temperature -40c to +85c load capacitance 18pf shunt capacitance 7pf maximum esr 25 w note: c y is load capacitance and rx is used to prevent osci llations at overtone frequency of the fundamental f requency. typical crystal interface circuit c y = 2*(c p C c s ), where c p = load capacitance of crystal from crystal vendor datasheet c s = stray capacitance due to c in, pcb, trace etc. c y rx c y crystal r xin xout
ASM3P2853a rev. 2 | page 4 of 7 | www.onsemi.com dc electrical characteristics parameter symbol conditions / description min typ max unit overall supply current, dynamic i dd v dd = 2.5v, f xin = 25mhz, c l = 15pf 7 13 20 ma supply current, static i ddl v dd = 2.5v, x in = 0, pwdnb = 0 - 12 - ua all input pins high-level input voltage v ih v dd = 2.5v 1.7 - - v low-level input voltage v il v dd = 2.5v - - 0.7 v high-level input current i ih - - 25 a low-level input current (pull-up) i il - - -25 a clock outputs high-level output source current i xoh v dd = 2.5v ,v(x in ) = 0, v o = 2v - -15 - ma low-level output sink current i xol v dd = v(x in ) = 2.5v, v o = 0.4v - 15 - ma high-level output source current i oh v o = 2v - 8 - ma low-level output sink current i ol v o = 0.4v - 8 - ma output impedance z o - 42 -
ASM3P2853a rev. 2 | page 5 of 7 | www.onsemi.com ac electrical characteristics parameter symbol conditions / description min typ max unit rise time 1 t r measured from 20% to 80% of the signal level - 2 - ns fall time 1 t f measured from 80% to 20% of the signal level - 1.5 - ns jitter (cycle-to-cycle) t jc - 250 - ps jitter (period) t p - 175 - ps clock duty cycle t d ratio of pulse width (as measured from rising edge to next falling edge at v dd /2) to one clock period 45 50 55 % power-up time t on first locked cycle after power-up (with stable v dd and valid input clock) - - 5 ms note: 1. c l = 15 pf, input clock frequency = 25mhz typical application schematic using ASM3P2853a devi ce modulated 50mhz output 1 2 3 4 xin xout v dd v ss usb clock 5 6 7 8 pwdnb ssonb b 50mhz 25mhz fundamental crystal + 2.5 v ASM3P2853a un-modulated 48mhz output 27pf 27pf 0.1u f
ASM3P2853a rev. 2 | page 6 of 7 | www.onsemi.com package information 8-pin soic package d e h d a1 a2 a q l c b e symbol dimensions inches millimeters min max min max a1 0.004 0.010 0.10 0.25 a 0.053 0.069 1.35 1.75 a2 0.049 0.059 1.25 1.50 b 0.012 0.020 0.31 0.51 c 0.007 0.010 0.18 0.25 d 0.193 bsc 4.90 bsc e 0.154 bsc 3.91 bsc e 0.050 bsc 1.27 bsc h 0.236 bsc 6.00 bsc l 0.016 0.050 0.41 1.27 0 8 0 8 coplanarity 4 mil
ASM3P2853a on semiconductor and are registered trademarks of semiconductor componen ts industries, llc (scillc). scillc reserves the ri ght to make changes without further notice to any products herein. sci llc makes no warranty, representation or guarantee regarding the suitability of its products for any p articular purpose, nor does scillc assume any liability arisi ng out of the application or use of any product or circuit, and specifically disclaims any and all lia bility, including without limitation special, consequential or incidental damages. typical parameters which may be provided in scillc data sheets and/or specifications can and do vary in different applica tions and actual performance may vary over time. al l operating parameters, including typicals must b e validated for each customer application by customer 's technical experts. scillc does not convey any l icense under its patent rights nor the rights of ot hers. scillc products are not designed, intended, or auth orized for use as components in systems intended fo r surgical implant into the body, or other applicat ions intended to support or sustain life, or for any oth er application in which the failure of the scillc p roduct could create a situation where personal inju ry or death may occur. should buyer purchase or use scillc pro ducts for any such unintended or unauthorized appli cation, buyer shall indemnify and hold scillc and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs , damages, and expenses, and reasonable attorney fe es arising out of, directly or indirectly, any claim of person al injury or death associated with such unintended or unauthorized use, even if such claim alleges tha t scillc was negligent regarding the design or manufacture o f the part. scillc is an equal opportunity/affirmat ive action employer. u.s patent pending; timing-sa fe and active bead are trademarks of pulsecore semicon ductor, a wholly owned subsidiary of on semiconduct or. this literature is subject to all applicable copyright laws and is not for resale in any manner. publication ordering information literature fulfillment: literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone: 303-675-2175 or 800-344-3860 toll free usa/canada fax: 303-675-2176 or 800-344-3867 toll free usa/canada email: orderlit@onsemi.com n. american technical support: 800-282-9855 toll free usa/canada europe, middle east and africa technical support: phone: 421 33 790 2910 japan customer focus center phone: 81-3-5773-3850 on semiconductor website: www.onsemi.com order literature: http://www.onsemi.com/orderlit for additional information, please contact your local sales representative ordering code part number marking package configuration temperature range ASM3P2853ag-08sr aec 8-pin soic, tape & reel, green 0c to +70c a microdot placed at the end of last row of marki ng or just below the last row toward the center of package indicates pb-free.
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