APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Features • Desktop/Notebook Computers • Spread Spectrum Clock Generator (SSCG) with 1x, 2x and 4x Outputs • Printers, Copiers and MFP • Scanners and Fax • 6 to 82 MHz operating frequency range. • LCD Displays and Monitors • Modulates external clocks including crystals, crystal oscillators and ceramic resonators. • CD-ROM, VCD and DVD • Programmable modulation with simple • Automotive and Embedded Systems R-C external loop filter (LF) • Networking, LAN/WAN • Center Spread Modulation. • Digital Cameras and Camcorders • 3 - 5 Volt power supply. • Modems • TTL/CMOS compatible outputs. Benefits • Low short term jitter. • Programmable EMI Reduction • Low Power Dissipation; • Fast Time to Market 3.3 VDC = 37 mw - typical • Lower cost of compliance 5.0 VDC = 115 mw - typical • No degradation in Rise/Fall times Available in 8 pin SOIC and TSSOP packages. • Lower component and PCB layer count • Applications Product Description The Cypress FS781/2/4 are Spread Spectrum Clock Generator ICs (SSCG) designed for the purpose of reducing Electro Magnetic Interference (EMI) found in today’s high-speed digital systems. The FS781/2/4 SSCG clocks use an IMI proprietary technology to modulate the input clock frequency, FSOUT by modulating the frequency of the digital clock. By modulating the reference clock the measured EMI at the fundamental and harmonic frequencies of FSOUT is greatly reduced. This reduction in radiated energy can significantly reduce the cost of complying with regulatory requirements without degrading digital waveforms. The Cypress FS781/2/4 clocks are very simple and versatile devices to use. By programming the two range select lines, S0 and S1, any frequency from 6 to 82 MHz operating range can be selected. The FS781/2/4 are designed to operate over a very wide range of input frequencies and provides 1x, 2x and 4x modulated clock outputs. The FS78x devices have a simple frequency selection table that allows operation from 6 MHz to 82 MHz in four separate ranges. The bandwidth of the frequency spread at FSOUT is determined by the values of the loop filter components. The modulation rate is determined internally by the input frequency and the selected input frequency range. The Bandwidth of these products can be programmed from as little as 0.6% up to as much as 4.0% by selecting the proper loop filter value. Refer to the Loop Filter Selection chart on page 6 for recommended values. Due to a wide range of application requirements, an external loop filter (LF) is used on the FS78x products. The user can select the exact amount of frequency modulation suitable for the application. Using a fix internal loop filter would severely limit the use of a wide range of modulation bandwidths (Spread %) to a few discrete values. Refer to FS791/2/4 products for applications requiring 80 to 140 MHz frequency range. Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 1 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Block Diagram Loop Filter 4(6) 250 K Xin Reference Divider 1(3) 8 pF Phase Detector VCO 10 pF. Xout Modulation Control 2(4) VCO / N 8 pF VDD 8(2) Power Contol Logic Output Divider and Mux VDD Input Control Logic VSS 5(7) 3(5) 7(1) VSS S1 S0 6(8) FSOUT (TSSOP Pin #) Figure 1. Block Diagram Ordering Information Product Number FS781BZB FS782BZB FS784BZB FS781BT FS781BT FS781BT Marking Example: FM-OUT Scaling 1xFin 2xFin 4xFin 1xFin 2xFin 4xFin Package Type 8 Pin 150 mil SOIC 8 Pin 150 mil SOIC 8 Pin 150 mil SOIC 8 Pin 169 mil TSSOP 8 Pin 169 mil TSSOP 8 Pin 169 mil TSSOP Production Flow Commercial, 0 to 70°C Commercial, 0 to 70°C Commercial, 0 to 70°C Commercial, 0 to 70°C Commercial, 0 to 70°C Commercial, 0 to 70°C Date Code FS781BZB Lot Number FS78xBZB Flow (“B” Flow not indicated on TSSOP package) Packages Z = SOIC (150 Mil) T = TSSOP (169 Mil) Revisions Device Number Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 2 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Pin Configuration Xin 1 8 VDD Xout 2 7 S0 S1 3 6 FSOUT LF 4 5 VSS FS78x 8 FSOUT 7 VSS 3 6 LF 4 5 S1 S0 1 VDD 2 Xin Xout FS78x 8 Pin TSSOP Package 8 Pin SOIC Package Pin Description Pin No. 1/2 Pin Name Xin / Xout I/O I/O TYPE Analog 7/3 S0 / S1 I CMOS/TTL 4 LF I Analog 6 FSOUT O CMOS/TTL 8 5 VDD VSS P P Power Power Description Pins form an on-chip reference oscillator when connected to terminals of an external parallel resonant crystal. Xin may be connected to TTL/CMOS external clock source. If Xin connected to external clock other than crystal, leave Xout (pin 2) unconnected. Digital control inputs to select input frequency range and output frequency scaling. Refer to Tables 7 & 8 for selection. S0 has internal pulldown. S1 has internal pullup. Loop Filter. Single ended tri-state output of the phase detector. A two-pole passive loop filter is connected to Loop Filter (LF). Modulated Clock Frequency Output. The center frequency is the same as the input reference frequency for FS781. Input frequency is multiplied by 2x and 4x for FS782 and FS784 respectively. Positive Power Supply. Power Supply Ground Table 1 Output Frequency Selection Product Number FS781 FS782 FS784 FSOUT Frequency Scaling 1x 2x 4x Description 1x Modulated Frequency of Input Clock 2x Modulated Frequency of Input Clock 4x Modulated Frequency of Input Clock Table 2. FSOUT SSCG (Modulated Output Clock) Product Selection Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 3 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK This device contains circuitry to protect the inputs against damage due to high static voltages or electric fields; however, precautions should be taken to avoid application of any voltage higher than the absolute maximum rated voltages to this circuit. For proper operation, Vin and Vout should be constrained to the range, VSS < (Vin or Vout) < VDD. All digital inputs are tied high or low internally. Refers to electrical specifications for operating supply range. Absolute Maximum Ratings Item Operating Voltage Input, relative to VSS Output, relative to VSS AVDD relative to DVDD AVSS relative to DVSS Temperature, Operating Temperature, Storage Symbol VDD VIRvss VORvss ∆Vpp ∆Vss TOP TST Min 3.0 -0.3 -0.3 -100 -100 0 - 65 Table 3 Max 6.0 VDD +0.3 VDD +0.3 +100 +100 + 70 + 150 Units VDC VDC VDC mV mV 0 C 0 C Electrical Characteristics Characteristic Symbol Min Typ Max Input Low Voltage VIL 0.3 * VDD Input High Voltage VIH 0.7 * VDD Input Low Current IIL 100 Input High Current IIH 100 Output Low Voltage IOL= 10mA, VDD = 5V VOL 0.4 Output High Voltage IOH = 10mA, VDD = 5V VOH VDD-1.0 Output Low Voltage IOL= 6mA, VDD = 3.3V VOL 0.4 Output High Voltage IOH = 5mA,VDD = 3.3V VOH 2.4 Resistor, Pull Down (Pin-7) Rpd 60K 125K 200K Resistor, Pull Up (Pin-3) Rpu 60K 125K 200K Input Capacitance (Pin-1) Cxin 8 Output Capacitance (Pin-2) Cxout 10 5 Volt Dynamic Supply Current (CL = No Load) ICC 38 3.3 Volt Dynamic Supply Current (CL = No Load) ICC 20 Short Circuit Current (FSOUT) ISC 25 BW% Variations, 3.30V** BW -20 0 +20 BW% Variations, 5.00V** BW -30 0 +30 Test measurements performed at VDD = 3.3V and 5.0V ±10%, Xin = 48 MHz, Ta = 0°C to 70°C **BW% Variations in % from the BW% values give in Loop Filter Value Tables. Table 4 Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** Units VDC VDC µA µA VDC VDC VDC VDC Ω Ω pF pF mA mA mA % % 05/07/2001 Page 4 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Timing Characteristics Characteristic Symbol Min Typ Max Units Output Rise Time Measured at 10% - 90% @ 5 VDC tTLH 2.0 2.2 2.5 ns Output Fall Time Measured at 10% - 90% @ 5 VDC tTHL 1.7 2.0 2.2 ns Output Rise Time Measured at 0.8V - 2.0V @ 5 VDC tTLH 0.50 0.65 0.75 ns Output Fall Time Measured at 0.8V - 2.0 V @ 5 VDC tTHL 0.50 0.65 0.75 ns Output Rise Time Measured at 10% - 90% @ 3.3 VDC tTLH 2.6 2.65 2.9 ns Output Fall Time Measured at 10% - 90% @ 3.3 VDC tTHL 2.0 2.1 2.2 ns Output Rise Time Measured at 0.8V - 2.0V @ 3.3 VDC tTLH 0.8 0.95 1.1 ns Output Fall Time Measured at 0.8V - 2.0 V @ 3.3 VDC tTHL 0.78 0.85 0.9 ns TsymF1 45 50 55 % FSOUT, Cycle to Cycle Jitter, 48 MHz @ 3.30 VDC (Pin 6) CCJ - 320 370 pS FSOUT, Cycle to Cycle Jitter, 48 MHz @ 5.0 VDC (Pin 6) CCJ - 310 360 pS FSOUT, Cycle to Cycle Jitter, 72 MHz @ 3.30 VDC (Pin 6) CCJ - 270 325 pS FSOUT, Cycle to Cycle Jitter, 72 MHz @ 5.0 VDC (Pin 6) CCJ - 390 440 pS Output Duty Cycle Measurements performed at VDD = 3.3 and 5.0V ± 10%, Ta = 0°C to 70°C, CL = 15pF, Xin = 48 MHz. Table 5 Range Selection Table S1 (pin 3) 0 0 1 1 S0 (pin 7) 0 1 0 1 Fin (MHz) (pin 2/3) 6 - 16 16 - 32 32 - 66 66 - 82 Modulation FS781 Rate FSOUT (pin 6) Fin/120 6 – 16 MHz Fin/240 16 – 32 MHz Fin/480 32 – 66 MHz Fin/720 66– 82 MHz Table 6 Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com FS782 FSOUT (pin 6) 12 – 32 MHz 32 – 64 MHz 64 – 82 MHz N/A Document#: 38-07029 Rev. ** FS784 FSOUT (pin 6) 32 – 64 MHz 64 – 82 MHz N/A N/A 05/07/2001 Page 5 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Loop Filter Selection Chart R6 LF (pin 4) The following table provides a list of recommended loop filter values for the FS781/2/4. The FS78x is divided into 4 ranges and operates at both 3.3 and 5.0 VDC. The loop filter at the right is representative of the loop filter components in the table below. C8 C7 FS781/2/4 Recommended Loop Filter Values. C7 (pF.) @ +3.3 VDC +/- 5% (R6 = 3.3K) Input (MHz) 6 8 10 12 14 16 S 1 0 0 0 0 0 0 S 0 0 0 0 0 0 1 BW = 1.0% (note 3) 10,000/1000 10,000/330 1040 830 580 10000 BW = 1.5% (note 3) 1550 990 680 420 230 980 BW = 2.0% (note 3) 910 820 460 300 200 760 BW = 2.5% (note 3) 780 640 360 220 160 580 BW = 3.0% (note 3) 700 520 300 200 140 470 BW = 3.5% (note 3) 640 450 240 190 100 410 BW = 4.0% (note 3) 560 400 210 170 80 385 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1000 960 920 660 470 470 330 10000 2200 1500 960 940 950 900 790 730 640 400 300 230 180 170 860 820 690 600 620 680 580 440 470 410 250 220 180 140 120 640 620 520 420 380 400 270 260 390 270 210 180 150 120 100 520 470 410 340 275 250 220 210 320 230 180 150 130 100 82 430 400 340 280 230 210 190 180 220 200 160 140 100 80 68 380 330 290 220 210 190 180 160 190 180 150 120 70 60 47 330 290 240 160 180 170 165 140 52 54 56 58 60 62 64 1 1 1 1 1 1 1 0 0 0 0 0 0 1 470 470 445 430 295 270 1180 325 270 250 210 185 220 860 220 200 185 165 150 150 560 185 170 150 130 120 120 410 155 140 120 100 100 100 340 135 130 85 65 90 82 290 120 100 47 33 82 68 230 66 68 70 72 74 76 78 80 82 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1180 1180 1120 1160 1110 1000 910 900 900 760 750 740 780 770 720 670 620 540 560 500 470 470 470 440 270 260 250 350 320 370 300 280 240 210 210 210 260 260 300 250 230 210 190 190 190 220 230 240 220 210 190 170 170 170 210 210 170 190 190 170 160 156 150 Notes: 1. 2. 3. 4. If the value selected from the above chart is not a standard, use the next available larger value. All Bandwidth’s indicated above are total peak-to-peak spread. 1% = +0.5% to –0.5%. 4% = +2.0% to –2.0%. If C8 is not listed in the chart for a particular BW and Freq., it is not used in the loop filter. Contact factory for LF (Loop Filter) values less than 1.0 % BW. Table 7 Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 6 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK FS781/2/4 Recommended Loop Filter Values. C7 (pF.) @ +5.0 VDC +/- 5% (R6 = 3.3K) Input (MHz) 6 8 10 12 14 16 S 1 0 0 0 0 0 0 S 0 0 0 0 0 0 1 BW = 1.0% (note 3) 1140 1170 1030 760 450 2490 BW = 1.5% (note 3) 1030 970 660 340 240 970 BW = 2.0% (note 3) 930 740 430 230 180 730 BW = 2.5% (note 3) 830 570 350 200 140 590 BW = 3.0% (note 3) 710 460 280 180 100 480 BW = 3.5% (note 3) 610 400 210 160 70 430 BW = 4.0% (note 3) 510 280 130 130 50 370 20 22 24 26 28 30 32 0 0 0 0 0 0 1 1 1 1 1 1 1 0 1360 990 820 530 430 250 Note 4. 680 560 360 270 230 200 1000 480 330 250 210 180 150 740 370 260 200 170 150 110 570 280 230 180 150 110 100 470 190 200 160 110 100 90 410 250 190 150 90 90 80 370 36 38 40 42 44 46 48 50 52 54 56 58 60 62 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 Note 4. Note 4. Note 4. 1030 790 1110 1110 830 560 510 470 450 430 Note 4. 970 880 800 680 560 420 280 330 340 280 210 220 240 800 670 560 460 360 260 280 200 200 205 180 160 250 120 580 480 380 290 260 220 210 190 180 170 140 120 110 90 430 380 310 240 220 200 180 170 160 140 110 100 90 80 330 310 270 230 200 190 170 140 130 120 110 90 80 80 250 230 220 220 190 170 140 120 110 90 90 90 80 70 180 66 68 70 72 74 76 78 80 82 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Note 4. Note 4. Note 4. Note 4. Note 4. Note 4. Note 4. Note 4. Note 4. 630 690 650 575 500 550 600 570 540 400 365 330 340 355 330 290 240 250 320 285 250 250 245 230 220 210 200 240 225 210 210 205 200 190 185 180 150 170 190 190 180 175 170 165 160 100 140 180 170 165 160 155 150 140 Notes: 1. 2. 3. 4. If the value selected from the above chart is not a standard value, use the next available larger value. All bandwidths indicated are total peak-to-peak spread. 1% = +0.5% to –0.5%. 4% = +2.0% to –2.0%. If C8 is not listed in the chart for a particular BW and Freq., it is not used in the loop filter. Contact Factory for these Loop Filter values and bandwidths less than 1.0%. Table 8 Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 7 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK SSCG Modulation Profile The digital control inputs S0 and S1 determine the modulation frequency of FS781/2/4 products. The input frequency is divided by a fixed number, depending on the operating range that is selected. The modulation frequency of the FS78x can be determined from the Table 8. To compute the modulation frequency enter to Table 8 with selected S0 and S1 values to obtain Modulation Divider Number, and divide the input frequency by this fix number. S1 S0 0 0 1 1 0 1 0 1 Input Frequency Range (MHz) 6 to 16 16 to 32 32 to 66 66 to 82 Modulation Divider Number 120 240 480 720 Table 9 + .5% 1.0% Total Xin - .5% TIME (microseconds) Figure 5. Frequency Profile in Time Domain With the correct loop filter connected to pin 4, the following profile will provide the best EMI reduction. This profile can be seen on a Time Domain Analyzer. Theory of Operation The FS781/2/4 devices are Phase Lock Loop (PLL) type clock generators using Direct Digital Synthesis (DDS). By precisely controlling the bandwidth of the output clock, the FS781/2/4 products become a Low EMI clock generator. The theory and detailed operation of these products will be discussed in the following sections. EMI All clocks generate unwanted energy in their harmonics. Conventional digital clocks are square waves with a duty cycle that is very close to 50 %. Because of the 50/50 duty cycle, digital clocks generate most of their harmonic rd th th energy in the odd harmonics, i.e.; 3 , 5 , 7 etc. It is possible to reduce the amount of energy contained in the fundamental and harmonics by increasing the bandwidth of the fundamental clock frequency. Conventional digital Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 8 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK clocks have a very high Q factor, which means that all of the energy at that frequency is concentrated in a very narrow bandwidth, consequently, higher energy peaks. Regulatory agencies test electronic equipment by the Amount of peak energy radiated from the equipment. By reducing the peak energy at the fundamental and harmonic frequencies, the equipment under test is able to satisfy agency requirements for Electro-Magnetic Interference (EMI). Conventional methods of reducing EMI have been to use shielding, filtering, multi-layer PCB’s etc. These FS781/2 and 4 use the approach of reducing the peak energy in the clock by increasing the clock bandwidth, and lowering the Q of the clock. SSCG The FS781/2/4 products use a unique method of modulating the clock over a very narrow bandwidth and controlled rate of change, both peak to peak and cycle to cycle. The FS78x products take a narrow band digital reference clock in the range 6 - 82 MHz and produce a clock that sweeps between a controlled start and stop frequency and precise rate of change. To understand what happens to an SSCG clock, consider that we have a 20 MHz clock with a 50 % duty cycle. From a 20 MHz clock we know the following; 50% 50% Tc = 50 ns. 20 MHz Unmodulated Clock Figure 6. Clock Frequency = Fc = 20 MHz. Clock Period = Tc = 1/20 MHz=50 ns Fc = 20 MHz Consider that this 20 MHz clock is applied to the Xin input of the FS78x, either as an externally driven clock or as the result of a parallel resonant crystal connected to pins 1 and 2 of the FS78x. Also consider that the products are operating from a 5-volt DC power supply and the loop filter is set for a total bandwidth spread of 2%. Refer to table 6 on page 6. From the above parameters, the output clock at FSOUT will be sweeping symmetrically around a center frequency of 20 MHz. The minimum and maximum extremes of this clock will be +200 kHz and -200 kHz. So, we have a clock that is sweeping from 19.8 MHz to 20.2 MHz and back again. If we were to look at this clock on a spectrum analyzer we would see the picture in figure 7. Keep in mind that this is a drawing of a perfect clock with no noise. Fmin = 19.8 MHz Fmax = 20.2 MHz Figure 7. Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 9 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK We see that the original 20 MHz reference clock is at the center Frequency, Cf, and the minimum and maximum extremes are positioned symmetrically about the center frequency. This type of modulation is called Center-Spread. Figure 8 shows a 20 MHz clock, as it would be seen on an oscilloscope. The top trace is the non-modulated reference clock,. The bottom trace is the modulated clock at pin 6. From this comparison chart you can see that the frequency is decreasing and the period of each successive clock is increasing. The Tc measurements on the left and right of the bottom trace indicate the max. and min. extremes of the clock. Intermediate clock changes are small and accumulate to achieve the total period deviation. The reverse of this figure would show the clock going from minimum extreme back to the high extreme. Tc =49.50 ns. Tc = 50.50 Figure 8. Period Comparison Chart Looking at figure 7, you will note that the peak amplitude of the 20 MHz non-modulated clock is higher than the wideband modulated clock. This difference in peak amplitudes between modulated and unmodulated clocks is the reason why SSCG clocks are so effective in digital systems. This figure refers to the fundamental frequency of a clock. A very important characteristic of the SSCG clock is that the bandwidth of the fundamental frequency is multiplied by the harmonic number. In other words, if the bandwidth of a 20 MHz clock is 200 kHz, the bandwidth rd of the 3 harmonic will be 3 times 200, or 600 kHz. The amount of bandwidth is relative to the amount of energy in the clock. Consequently, the wider the bandwidth, the greater the energy reduction of the clock. Most applications will not have a problem meeting agency specifications at the fundamental frequency. It is the higher harmonics that usually cause the most problems. With an SSCG clock, the bandwidth and peak energy th reduction increases with the harmonic number. Consider that the 11 harmonic of a 20 MHz clock is 220 MHz. th With a total spread of 200 kHz at 20 MHz, the spread at the 11 harmonic would be 2.20 MHz which greatly reduces the peak energy content. It is typical to see as much as 12 to 18 dB. reduction at the higher harmonics, due to a modulated clock. The difference in the peak energy of the modulated clock and the non-modulated clock in typical applications will see a 2 - 3 dB. reduction at the fundamental and as much as 8 - 10 dB. reduction at the intermediate harmonics, rd th th 3 , 5 , 7 etc. At the higher harmonics, it is quite possible to reduce the peak harmonic energy, compared to the unmodulated clock, by as much as 12 to 18 dB. Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 10 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Application Notes and Schematic The schematic at the right is configured for the following parameters; Package selected = FS781 Xin = 20 MHz Crystal FSOUT = 20 MHz (S0=1 and S1=0) Bandwidth of the FSOUT clock is determined by the values of the loop filter connected to pin 4. Crystal is 20 MHz is 1st Order w ith 18 pF load capacitance. C2 1 If Crystal load capacitance is different than 18 pF, C1 and C2 must be re-calculated. For third overtone crystals, a parallel or series resonant trap is required. 20 M Hz 27 pF Xin VDD 8 C3 2 VDD C1 0.1 uF Y1 Xout S0 7 FS781 27 pF 3 4 Mount loop filter components as close to LF pin as possible. S1 FSOUT LF VSS 6 FSOUT 5 R6 C7 C8 ** ** Occasionally, C8 is used to create a second pole for this loop filter. Refer to Loop Filter Selection table. . Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 11 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Package Drawing and Dimensions 8 Pin SOIC Outline Dimensions INCHES SYMBOL C H NOM MILLIMETERS NOM MAX A 0.053 - 0.069 1.35 - 1.75 A1 0.004 - 0.010 0.10 - 0.25 MAX MIN A2 0.047 - 0.059 1.20 - 1.50 B 0.013 - 0.020 0.33 - 0.51 C 0.007 - 0.010 0.19 - 0.25 D 0.189 - 0.197 4.80 - 5.00 E 0.150 - 0.157 3.80 - 4.00 e L E MIN 0.050 BSC 1.27 BSC H 0.228 - 0.244 5.80 - 6.20 L 0.016 - 0.050 0.40 - 1.27 a 0º - 0º - 8º 8º 8 Pin TSSOP Outline Dimensions a D A2 A INCHES SYMBOL A A1 B e MIN - NOM - MILLIMETERS MAX 0.047 MIN - NOM MAX - 1.20 A1 0.002 - 0.006 0.05 - 0.15 A2 0.031 0.039 0.041 0.80 1.00 1.05 B 0.007 - 0.012 0.19 - 0.30 C 0.004 - 0.008 0.09 - 0.20 D 0.114 0.118 0.122 2.90 3.00 3.10 E 0.169 0.173 0.177 4.30 4.40 4.50 e 0.026 BSC 0.65 BSC H 0.244 0.252 0.260 6.20 6.40 6.60 L 0.018 0.024 0.030 0.45 0.60 0.75 a 0º - 0º - 8º 8º Cypress Semiconductor Corporation Disclaimer Cypress Semiconductor Corporation reserves the right to change or modify the information contained in this data sheet, without notice. Cypress Semiconductor Corporation does not assume any liability arising out of the application or use of any product or circuit described herein Cypress Semiconductor Corporation does not convey any license under its patent rights nor the rights of others. Cypress Semiconductor Corporation does not authorize its products for use as critical components in life-support systems or critical medical instruments, where a malfunction or failure may reasonably be expected to result in significant injury to the user. Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Document#: 38-07029 Rev. ** 05/07/2001 Page 12 of 13 APPROVED PRODUCT FS781/82/84 LOW EMI SPECTRUM SPREAD CLOCK Document Title: FS781/82/84 Low EMI Spectrum Spread Clock Document Number: 38-07029 Rev. ** ECN No. 106957 Issue Date 06/11/01 Orig. of Change IKA Cypress Semiconductor Corporation 525 Los Coches St. Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571 http://www.cypress.com Description of Change Convert from IMI to Cypress Document#: 38-07029 Rev. ** 05/07/2001 Page 13 of 13