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| W183 Full Feature Peak Reducing EMI Solution Features * Cypress PREMISTM family offering * Generates an EMI optimized clocking signal at the output * Selectable output frequency range * Single 1.25%, 3.75% down or center spread output * Integrated loop filter components * Operates with a 3.3 or 5V supply * Low power CMOS design * Available in 14-pin SOIC (Small Outline Integrated Circuit) Table 1. Modulation Width Selection SS% 0 1 W183 Output Fin Fout Fin - 1.25% Fin Fout Fin - 3.75% W183-5 Output Fin + 0.625% Fin - 0.625% Fin + 1.875% Fin -1.875% Table 2. Frequency Range Selection FS2 0 0 1 1 FS1 0 1 0 1 Frequency Range 28 MHz FIN 38 MHz 38 MHz FIN 48 MHz 46 MHz FIN 60 MHz 58 MHz FIN 75 MHz Key Specifications Supply Voltages: ........................................... VDD = 3.3V5% or VDD = 5V10% Frequency Range: ............................ 28 MHz Fin 75 MHz Crystal Reference Range:................. 28 MHz Fin 40 MHz Cycle to Cycle Jitter: ....................................... 300 ps (max.) Selectable Spread Percentage: ....................1.25% or 3.75% Output Duty Cycle: ............................... 40/60% (worst case) Output Rise and Fall Time: .................................. 5 ns (max.) Simplified Block Diagram 3.3V or 5.0V Pin Configuration SOIC FS2 CLKIN or X1 NC or X2 GND GND SS% FS1 1 2 3 4 5 6 14 13 12 11 10 9 8 REFOUT OE# SSON# Reset VDD VDD CLKOUT W183/W183-5 X1 XTAL Input X2 40 MHz Max W183 Spread Spectrum Output (EMI suppressed) 7 3.3V or 5.0V Oscillator or Reference Input W183 Spread Spectrum Output (EMI suppressed) PREMIS is a trademark of Cypress Semiconductor Corporation. Cypress Semiconductor Corporation * 3901 North First Street * San Jose * CA 95134 * 408-943-2600 July 25, 2000, rev.*B W183 Pin Definitions Pin Name CLKOUT REFOUT Pin No. 8 14 Pin Type O O Pin Description Output Modulated Frequency: Frequency modulated copy of the input clock (SSON# asserted). Non-Modulated Output: This pin provides a copy of the reference frequency. This output will not have the Spread Spectrum feature regardless of the state of logic input SSON#. Crystal Connection or External Reference Frequency Input: This pin has dual functions. It may either be connected to an external crystal, or to an external reference clock. Crystal Connection: Input connection for an external crystal. If using an external reference, this pin must be left unconnected. Spread Spectrum Control (Active LOW): Asserting this signal (active LOW) turns the internal modulation waveform on. This pin has an internal pull-down resistor. Modulation Width Selection: When Spread Spectrum feature is turned on, this pin is used to select the amount of variation and peak EMI reduction that is desired on the output signal. This pin has an internal pull-up resistor. Output Enable (Active LOW): When this pin is held HIGH, the output buffers are placed in a high-impedance mode. This pin has an internal pull-down resistor. Modulation Profile Restart: A rising edge on this input restarts the modulation pattern at the beginning of its defined path. This pin has an internal pull-down resistor. Frequency Selection Bits: These pins select the frequency range of operation. Refer to Table 2. These pins have internal pull-up resistors. Power Connection: Connected to 3.3V or 5V power supply. Ground Connection: Connect all ground pins to the common ground plane. CLKIN or X1 2 I NC or X2 SSON# 3 12 I I SS% 6 I OE# 13 I Reset 11 I FS1:2 VDD GND 7, 1 9, 10 4, 5 I P G 2 W183 Overview The W183 product is one of a series of devices in the Cypress PREMIS family. The PREMIS family incorporates the latest advances in PLL spread spectrum frequency synthesizer techniques. By frequency modulating the output with a low frequency carrier, peak EMI is greatly reduced. Use of this technology allows systems to pass increasingly difficult EMI testing without resorting to costly shielding or redesign. In a system, not only is EMI reduced in the various clock lines, but also in all signals which are synchronized to the clock. Therefore, the benefits of using this technology increase with the number of address and data lines in the system. The Simplified Block Diagram shows a simple implementation. times the reference frequency. (Note: For the W183 the output frequency is equal to the input frequency.) The unique feature of the Spread Spectrum Frequency Timing Generator is that a modulating waveform is superimposed at the input to the VCO. This causes the VCO output to be slowly swept across a predetermined frequency band. Because the modulating frequency is typically 1000 times slower than the fundamental clock, the spread spectrum process has little impact on system performance. Frequency Selection With SSFTG In Spread Spectrum Frequency Timing Generation, EMI reduction depends on the shape, modulation percentage, and frequency of the modulating waveform. While the shape and frequency of the modulating waveform are fixed for a given frequency, the modulation percentage may be varied. Using frequency select bits (FS2:1 pins), the frequency range can be set (see Table 2). Spreading percentage is set with pin SS% as shown in Table 1. A larger spreading percentage improves EMI reduction. However, large spread percentages may either exceed system maximum frequency ratings or lower the average frequency to a point where performance is affected. For these reasons, spreading percentages between 0.5% and 2.5% are most common. Functional Description The W183 uses a phase-locked loop (PLL) to frequency modulate an input clock. The result is an output clock whose frequency is slowly swept over a narrow band near the input signal. The basic circuit topology is shown in Figure 1. The input reference signal is divided by Q and fed to the phase detector. A signal from the VCO is divided by P and fed back to the phase detector also. The PLL will force the frequency of the VCO output signal to change until the divided output signal and the divided reference signal match at the phase detector input. The output frequency is then equal to the ratio of P/Q VDD Clock Input Freq. Divider Q Phase Detector Charge Pump Reference Input VCO Post Dividers CLKOUT (EMI suppressed) Modulating Waveform Feedback Divider P PLL GND Figure 1. Functional Block Diagram 3 W183 Spread Spectrum Frequency Timing Generation The device generates a clock that is frequency modulated in order to increase the bandwidth that it occupies. By increasing the bandwidth of the fundamental and its harmonics, the amplitudes of the radiated electromagnetic emissions are reduced. This effect is depicted in )LJXUH . As shown in )LJXUH , a harmonic of a modulated clock has a much lower amplitude than that of an unmodulated signal. The reduction in amplitude is dependent on the harmonic number and the frequency deviation or spread. The equation for the reduction is: dB = 6.5 + 9*log10(P) + 9*log10(F) Where P is the percentage of deviation and F is the frequency in MHz where the reduction is measured. The output clock is modulated with a waveform depicted in )LJXUH . This waveform, as discussed in "Spread Spectrum Clock Generation for the Reduction of Radiated Emissions" by Bush, Fessler, and Hardin produces the maximum reduction in the amplitude of radiated electromagnetic emissions.)LJXUH details the Cypress spreading pattern. Cypress does offer options with more spread and greater EMI reduction. Contact your local Sales representative for details on these devices. EMI Reduction SSFTG Typical Clock Amplitude (dB) Amplitude (dB) Spread Spectrum Enabled NonSpread Spectrum Frequency Span (MHz) Center Spread Frequency Span (MHz) Down Spread Figure 2. Clock Harmonic with and without SSCG Modulation Frequency Domain Representation MAX. FREQUENCY 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 10% 20% 30% 40% 50% 60% 70% 80% 90% MIN. Figure 3. Typical Modulation Profile 4 100% W183 Absolute Maximum Ratings Stresses greater than those listed in this table may cause permanent damage to the device. These represent a stress rating only. Operation of the device at these or any other conditions . above those specified in the operating sections of this specification is not implied. Maximum conditions for extended periods may affect reliability. Rating -0.5 to +7.0 -65 to +150 0 to +70 -55 to +125 0.5 Unit V C C C W Parameter VDD, VIN TSTG TA TB PD Description Voltage on any pin with respect to GND Storage Temperature Operating Temperature Ambient Temperature under Bias Power Dissipation DC Electrical Characteristics: 0C < TA < 70C, VDD = 3.3V 5% Parameter IDD tON VIL VIH VOL VOH IIL IIH IOL IOH CI RP ZOUT Description Supply Current Power Up Time Input Low Voltage Input High Voltage Output Low Voltage Output High Voltage Input Low Current Input High Current Output Low Current Output High Current Input Capacitance Input Pull-Up Resistor Clock Output Impedance 500 25 Note 1 Note 1 @ 0.4V, VDD = 3.3V @ 2.4V, VDD = 3.3V 15 15 7 2.4 -50 50 2.4 0.4 First locked clock cycle after Power Good Test Condition Min. Typ. 18 Max. 32 5 0.8 Unit mA ms V V V V A A mA mA pF k Note: 1. Inputs FS1:2 have a pull-up resistor, Input SSON# has a pull-down resistor. 5 W183 DC Electrical Characteristics: 0C < TA < 70C, VDD = 5V 10% Parameter IDD tON VIL VIH VOL VOH IIL IIH IOL IOH CI RP ZOUT Description Supply Current Power Up Time Input Low Voltage Input High Voltage Output Low Voltage Output High Voltage Input Low Current Input High Current Output Low Current Output High Current Input Capacitance Input Pull-Up Resistor Clock Output Impedance 500 25 Note 2 Note 2 @ 0.4V, VDD = 5V @ 2.4V, VDD = 5V 24 24 7 2.4 -50 50 0.7VDD 0.4 First locked clock cycle after Power Good Test Condition Min. Typ. 30 Max. 50 5 0.15VDD Unit mA ms V V V V A A mA mA pF k AC Electrical Characteristics: TA = 0C to +70C, VDD = 3.3V 5% or 5V10% Symbol fIN fOUT fXOSC tR tF tOD tID tJCYC Parameter Input Frequency Output Frequency Crystal Oscillator Frequency Output Rise Time Output Fall Time Output Duty Cycle Input Duty Cycle Jitter, Cycle-to-Cycle Harmonic Reduction fout = 40 MHz, third harmonic measured, reference board, 15-pF load 8 15-pF load, 0.8V-2.4V 15-pF load, 2.4V-0.8V 15-pF load 40 40 250 Test Condition Input Clock Spread Off Min. 28 28 28 2 2 Typ. Max. 75 75 40 5 5 60 60 300 Unit MHz MHz MHz ns ns % % ps dB Note: 2. Inputs FS2:1 have a pull-up resistor, Input SSON# has a pull-down resistor. 6 W183 Application Information Recommended Circuit Configuration For optimum performance in system applications the power supply decoupling scheme shown in Figure 4 should be used. VDD decoupling is important to both reduce phase jitter and EMI radiation. The 0.1-F decoupling capacitor should be placed as close to the VDD pin as possible, otherwise the increased trace inductance will negate its decoupling capability. The 10-F decoupling capacitor shown should be a tantalum type. For further EMI protection, the VDD connection can be made via a ferrite bead, as shown. Recommended Board Layout Figure 5 shows a recommended a 2-layer board layout Xtal Connection or Reference Input Xtal Connection or NC GND 1 2 3 4 5 6 7 W183 14 13 12 11 10 9 8 R1 Clock Output C1 0.1 F C3 0.1 F 3.3V or 5V System Supply FB C2 10 F Tantalum Figure 4. Recommended Circuit Configuration C1, C3 = High frequency supply decoupling capacitor (0.1-F recommended). C2 = Common supply low frequency decoupling capacitor (10-F tantalum recommended). R1 = Match value to line impedance FB = Ferrite Bead = Via T GND Plane o Xtal Connection or Reference Input Xtal Connection or NC G G C3 G C1 G G Clock Output R1 G Power Supply Input (3.3V or 5V) FB C2 Figure 5. Recommended Board Layout (2-Layer Board) Ordering Information Ordering Code W183 W183-5 Document #: 38-00798-B Package Name G Package Type 14-Pin Plastic SOIC (150-mil) 7 W183 Package Diagram 14-Pin Small Outline Integrated Circuit (SOIC, 150-mil) (c) Cypress Semiconductor Corporation, 2000. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges. |
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