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alliance semiconductor 2575 augustine drive ? santa clara ca ? tel: 408-855-4900 ? fax: 408-855-4999 ? www.alsc.com rev 1.0 october 2003 asm3p2508 a features generates an emi optimized clocking signal at output. input frequency ? 14.31818 mhz. frequency outputs: o 120 mhz (modulated) - default. o 72 mhz (modulated) or 48 mhz (modulated) selectable via i2c 1% centre spread. modulation rate: 40 khz. byte write via i2c supply voltage range 3.3v ( 0.3v). available in 8-pin soic package. commercial and industrial temperature range. product description the asm3p2508a is a versatile spread spectrum frequency modulator. the asm3p2508a reduces electromagnetic interference (emi) at the clock source. the asm3p2508a allows significant system cost savings by reducing the number of circuit board layers and shielding that are required to pass emi regulations. the asm3p2508a modulates the output of pll in order to spread the bandwidth of a synthesized clock, thereby decreasing the peak amplitu des of its harmonics. this 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 signal?s bandwidth is called spread spectrum clock generation. the asm3p2508a has a feature to power down the 72mhz / 48mhz output by writing data into specific registers in the device via i2c. by writing a ?0? into bit 1 of byte 0, the pll block generating 72 mhz / 48mhz can be powered down. writing ?0? into bit ?7? of byte 1 selects an output of 72 mhz on fout2clk while a ?1? at the same location selects a 48 mhz clo ck output. however, the i2c block, crystal oscillator, and the pll block generating 120mhz would be always running. block diagram sda crystal oscillator pll 1 scl fout2clk (72 mhz / 48 mhz) xin xout v ss v dd fout1clk (120 mhz) i2c interface pll 2
peak reducing emi solution 2 of 13 rev 1.0 october 2003 asm3p2508 a pin configuration pin description pin name type description xin i connection to crystal xout o connection to crystal v dd p power supply for the analog and digital blocks fout1clk o clock output-1 (120 mhz) - default fout2clk o clock output -2 ( 72 mhz / 48 mhz) sda i/o i2c data scl i i2c clock v ss p ground to entire chip fout1clk 8 7 6 5 fout2clk sda scl v ss xout 1 2 3 4 xin v dd asm3p2508a
peak reducing emi solution 3 of 13 rev 1.0 october 2003 asm3p2508 a absolute maximum ratings symbol parameter rating unit v dd supply voltage, dc (v ss ? 0.5) to 7 v v i input voltage, dc (v ss -0.5) to (v dd +0.5) v v o output voltage, dc (v ss -0.5) to (v dd + 0.5) v i ik input clamp current (v i <0 or v i >v dd ) -50 to +50 ma i ok output clamp current (v i <0 or v i >v dd ) -50 to +50 ma t s storage temperature -65 to +125 c t a ambient temperature range, under bias -55 to 125 c t j junction temperature 150 c lead temperature (soldering 10 sec) 260 c input static discharge voltage protection (mil ?std 883e, method 3015.7) 2 kv note: these are stress ratings only and functional oper ation is not implied. exposure to absolute maximum ratings for extended periods may affect device reliability. operating conditions parameter symbol condition / description min typ max unit supply voltage v dd 3.3v 10% 3 3.3 3.6 v ambient operating temperature range t a -10 +70 c crystal resonator frequency f xin 14.31818 mhz output driver load capacitance c l 15 pf
peak reducing emi solution 4 of 13 rev 1.0 october 2003 asm3p2508 a dc electrical characteristics parameter symbol conditions / description min typ max unit overall supply current, dynamic i dd v dd =3.3v, f clk =14.31818mhz, c l =15pf 43 ma supply current, static i ddl v dd = 3.3v, software power down tbd ma all input pins high-level input voltage v ih v dd =3.3v 2.0 v dd +0.3 v low-level input voltage v il v dd =3.3v v ss -0.3 0.8 v high-level input current i ih -1 1 clock outputs (fout1clk, fout2clk) high-level output source current i oh v o =2.4v -20 ma low-level output sink current i ol v o =0.4v 23 ma output impedance z oh v o =0.5v dd ; output driving high 29 ? z ol vo=0.5v dd ; output driving low 27
peak reducing emi solution 5 of 13 rev 1.0 october 2003 asm3p2508 a ac electrical characteristics parameter symbol conditions/ description min typ max unit rise time t r v o = 0.3v to 3.0v; cl = 15pf 2.1 ns fall time t f v o = 3.0v to 0.3v; cl = 15pf 1.9 ns clock duty cycle ratio of pulse width (as measured from rising edge to next falling edge at 2.5v) to one clock period 45 55 % on rising edges 500 us apart at 2.5 v relative to an ideal clock, pll b inactive * 45 ps jitter, long term tj (lt) on rising edges 500 us apart at 2.5 v relative to an ideal clock, pll b active * 165 from rising edge to next rising edge at 2.5 v, pll b inactive * 110 ps jitter, peak to peak tj ( ? t) from rising edge to next rising edge at 2.5 v, pll b active * 390 clock stabilization time t stb output active from power up, run mode via software power down 125 us * cl = 15 pf, fxin = 14.31818 mhz, fout = 50 mhz crystal specifications fundamental at cut parallel resonant crystal nominal frequency 14.31818 mhz frequency tolerance +/- 50 ppm or better at 25c operating temperature range -20c to +85c storage temperature -40c to +85c load capacitance 18pf shunt capacitance 7 pf maximum esr 25 ?
peak reducing emi solution 6 of 13 rev 1.0 october 2003 asm3p2508 a general i2c serial interface information the information in this section assumes familiarity with i2c programming. how to write through i2c: ? master (host) sends a start bit. ? master (host) sends the write address xx (h) ? asm3p2508a device will acknowledge ? master (host) sends the beginning byte location (=n) ? asm3p2508a device will acknowledge ? master (host) sends a dummy byte count ? asm3p2508a device will acknowledge ? master (host) starts sending byte n through byte n+x ? 1* ? asm3p2508a device will acknowledge each byte one at a time. ? master (host) sends a stop bit controller (host) asm3p2508a (slave/receiver) start bit slave address xx(h) ack beginning byte location (=n) ack dummy byte count ack beginning byte (byte n) ack next byte (byte n+1) ack ------- ---- last byte (bye n+x-1) ack stop bit how to read through i2c: ? master (host) will send start bit. ? master (host) sends the write address xx (h) ? asm3p2508a device will acknowledge ? master (host) sends the beginning byte location (=n) ? asm3p2508a device will acknowledge ? master (host) will send a separate start bit ? master (host) sends the read address xx (h) ? asm3p2508a device will acknowledge ? asm3p2508a device will send the dummy byte count ? master (host) acknowledges ? asm3p2508a device sends byte n through byte n+x ? 1* ? master (host) will need to acknowledge each byte ? master (host) will send a stop bit (* x is the number of bytes) controller (host) asm3p2508a (slave/receiver) start bit slave address xx(h) ack beginning byte = n ack repeat start slave address ack dummy byte count ack beginning byte n ack next byte n+1 ack ---- ------- last byte (byte n+x-1) not acknowledge stop bit
peak reducing emi solution 7 of 13 rev 1.0 october 2003 asm3p2508 a software a demonstration board and software is available for the asm3p2508a. the software can operate under windows 95 and windows nt. the opening screen of the software is shown in figure 2. opening screen by pressing the drop down arrow of port id toolbar button, any of the three parallel ports ( lpt1 lpt2 or lpt3 ) can be selected. the selected parallel port is used for the i2c data transfer.
peak reducing emi solution 8 of 13 rev 1.0 october 2003 asm3p2508 a programming the plls: select the cgen check box to enable the pll and the emi reduction check box to enable the spread spectrum on. enter the input frequency (in mhz), output frequency (mhz) , percentage error and modulation rate (khz) in the respective input boxes. to enable the out1 out2 and refout click the respective check box. to tristate all the outputs click the tristate check box. select the type of the modulation between the center or down and enter the deviation (percentage) in the respective input box. profile type can be selected between the sine triangular or lexmark. emi reduction enable/disable option is only available for the pll1. writing the data to the chip: there are two different ways of writing data to the chip. 1. writing through the file. 2. enter the required data in the respective forms and calculate and then write. for example: 1. enter the input freq say 15 mhz, in the input frequency box. 2. enter the required output frequency say 65 mhz, in the out1 frequency box. 3. enter the percentage error say 0.01 in the error box. 4. enter the modulation rate say 30 khz in the modulation rate box. 5. select the second output frequency by pressing the pull down menu of the out2 frequency. the value of out2 frequency can be selected as vco/2, vco/3, vco/4, vco/5, vco/6, vco/8, vco/9, vco/10, vco/12, vco/15, vco/18, vco/24 or vco/30. 6. select the type of the deviation, percentage deviation and type of the profile. 7. enter the data for pll2 in a similar manner. 8. press the calcresult button to load the data in the rom data panel. 9. to write this data to the chip press the i2cwrite button.
peak reducing emi solution 9 of 13 rev 1.0 october 2003 asm3p2508 a results window reading the data from the chip 1. to read the data from the chip through i2c, press the i2cread button. 2. the data can be seen in the rom data field. 3. this data which is read from the chip can be saved in the file by clicking the save button. an example of a byte write via i2c to partially ?power down? the device: asm3p2508a can be partially ?powered down? using bit 1 of byte 0. the organization of the register bits for byte ?0? is given with default values below: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 resv. resv. resv. resv. resv. resv. pll2 enable pll1 enable 0 1 0 1 0 1 1 1 the function of partial power down of the device is of interest to us - that is bit 1 of byte 0. in the default mode this bit is logic ?1?. as such, the byte 0 default value is 57 (h). to put asm3p 2508a in ?power down? mode, the bit 0 of byte 0 is to be changed to logic ?0?. hence writing a 55 (h) via i2c into byte 0 would put the device in partial ?power down? mode where the pll block generating 72 mhz / 48 mhz would be powered down while i2c block, crystal oscillator, and the pll block generating 120 mhz would still be active. the organization of the register bits is as below: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 resv. resv. resv. resv. resv. resv. pll2 enable pll1 enable 0 1 0 1 0 1 0 1
peak reducing emi solution 10 of 13 rev 1.0 october 2003 asm3p2508 a package information 8-pin soic symbol dimensions in inches dimensions in millimeters min max min max a 0.053 0.069 1.35 1.75 a1 0.004 0.010 0.10 0.25 b 0.013 0.022 0.33 0.53 c 0.007 0.012 0.18 0.27 d 0.188 0.197 4.78 5.00 e 0.150 0.158 3.80 4.01 h 0.228 0.244 5.80 6.20 e 0.050 bsc 1.27 bsc l 0.016 0.035 0.40 0.89 0 8 0 8
peak reducing emi solution 11 of 13 rev 1.0 october 2003 asm3p2508 a ordering codes part number package configuration asm3p2508a-08-st 8-pin soic tube asm3p2508a-08-sr 8-pin soic tape and reel asm3i2508a-08-st 8-pin soic tube ASM3I2508A-08-SR 8-pi n soic tape and reel
peak reducing emi solution 12 of 13 rev 1.0 october 2003 asm3p2508 a ? copyright 2003 alliance semiconductor corporation. all rights reserved. our three-point logo, our name and intelliwatt are trademarks or registered trademarks of alliance. all other brand and product names may be the trademarks of their respective companies. alliance reserves the right to make ch anges to this document and its products at any time without notice. alliance assumes no responsibility for any errors t hat may appear in this document. the data contained herein represents alliance's best data and/or estimate s at the time of issuance. alliance rese rves the right to change or correct this data at any time, without notice. if the product described herein is under development, significant changes to these specifications are possible. the information in this product data sheet is intended to be general descriptive information for potential customers and users, and is not in tended to operate as, or provide, any guarantee or warrantee to any user or customer. alliance does not assume any responsibility or lia bility arising out of the applic ation or use of any product described herein, and disclaims any express or implied warrant ies related to the sale and/or use of alliance products including liability or warranties related to fitness for a particular purpose, mercha ntability, or infringement of any intellec tual property rights, except as express agreed to in alliance's terms and conditions of sale (which are available from alliance). all sales of alliance products are made exclusively according to alliance's terms and conditions of sale. the purchase of products from alliance does not convey a license under any pa tent rights, copyrights; mask works rights, trademarks, or any other intellectual property rights of alli ance or third parties. alliance does not aut horize its products for use as critical components in life-supporting systems where a malfunction or fa ilure may reasonably be expected to result in significant injury to the user, and the inclusion of alliance products in such life-supporting systems implies that the manufacturer assumes all risk of such use and agrees to indemnify alliance against all claims arising from such use. alliance semiconductor corporation 2595, augustine drive, santa clara, ca 95054 tel# 408-855-4900 fax: 408-855-4999 www.alsc.com copyright ? alliance semiconductor all rights reserved preliminary information part number: asm3p2508a document version: v1.0
peak reducing emi solution 13 of 13 rev 1.0 october 2003 asm3p2508 a

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