Spread Spectrum Clock Generator

Transcription

1 Spread Spectrum Clock Generator DESCRIPTION is a clock generator for EMI (Electro Magnetic Interference) reduction. The peak of unnecessary (EMI) can be attenuated by making the oscillation frequency slightly modulate periodically with the internal modulator. accepts an input clock either from a fundamental Crystal or from an external reference (AC ordc coupled to XIN/CLKIN) and locks on to it delivering a 1x modulated clock output. FEATURE Power down pin : 4 µa (Typ-sample) consumption current at power down Input frequency : 10.0 MHz to 94.0 MHz Output frequency : 10.0 MHz to 94.0 MHz (One-fold input frequency) Analog Deviation Selection Modulation clock output Duty : 40% to 60% Modulation clock Cycle-Cycle Jitter : Less than 50 ps Power supply voltage : 2.5V--3.3 V Package : 8-pin TDFN Operating temperature : 40 C to +85 C Application Applications including USB and SATA. Can be usde for EMI reduction suchas GPS,LCD panel Etc. 1/14

2 BLOCK DIAGRAM VDD 8 XIN / CKIN 1 Clock input FREQ0 2 3 Clock out Frequency setting PLL block Modulation clock output 5 ModCK OUT ADS 7 Analog Deviation setting FREQ1 6 Frequency setting 4 GND 1 M Frequency setting Reference clock 1 N Phase compare Charge pump V/I conversion IDAC ICO Modulation clock output Loop filter 1 L PLL block Modulation logic Modulation rate setting/ Modulation enable setting A glitchless IDAC (current output D/A converter) provides precise modulation, thereby dramatically reducing EMI. 2/14

3 PIN ASSIGNMENT TOP VIEW XIN / CKIN 1 8 VDD FREQ ADS FREQ1 GND 4 5 ModCK OUT TDFN-8P PIN DESCRIPTION Pin name I/O Pin no. Description XIN / CKIN I 1 Clock input pin (or External reference clock input). 1 2 Crystal connection( external reference, this pin should be left open) FREQ0 1 3 Frequency setting pin GND GND pin ModCK OUT O 5 Modulation clock output FREQ1 I 6 Frequency setting pin ADS I 7 Analog Deviation Selection through external resistor to GND. VDD Power supply voltage pin 3/14

4 PIN SETTING When changing the pin setting, the stabilization wait time for the modulation clock required. The stabilization wait time for the modulation clock takes the maximum value of Lock-Up time in ELECTRICAL CHARACTER- ISTICS AC Characteristics. ADS modulation enable setting Resistance(K ohm) Deviation(+/-%) 0-500K Note : Analog Deviation Selection through external resistor to GND. Spectrum is spread (modulated) by centering on the input frequency. FREQ0, FREQ1 frequency setting FREQ0 FREQ1 Input frequency range L H 10 MHz to 30 MHz L L 20 MHz to 54 MHz H H 60 MHz to 94 MHz H L 40 MHz to 60 MHz Note : It is set according to the frequency of the clock input to the device. Set FREQ0 pin to H for the pin opened because FREQ0 pin has pull-up resistor. 4/14

5 ABSOLUTE MAXIMUM RATINGS Parameter Symbol Rating Min Max Unit Power supply voltage* VDD V Input voltage* VI VSS 0.5 VDD V Output voltage* VO VSS 0.5 VDD V Storage temperature TST C Operation junction temperature TJ C Outut p current IO ma Overshoot VIOVER VDD (tover 50 ns) V Undershoot VIUNDER VSS 1.0 (tunder 50 ns) V * : The parameter is based on VSS = 0.0 V. WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings. Overshoot/Undershoot VIOVER VDD V tunder 50 ns VDD Input pin VSS tover 50 ns VIUNDER VSS 1.0 V 5/14

6 ELECTRICAL CHARACTERISTICS DC Characteristics Parameter Symbol Pin Conditions Output voltage VOH H level output IOH = 4 ma (Ta = 40 C to + 85 C, VDD = 3.3 V ± 0.3 V, VSS = 0.0 V) Value Min Typ Max Unit VDD 0.5 VDD V VOL L level output IOL = 4 ma VSS 0.4 V Output impedance ZO 10 MHz to 94 MHz 35 Ω Input capacitance CIN CKIN, FREQ0, FREQ1, Ta = + 25 C, VDD = VI = 0.0 V, f = 1 MHz 16 pf Load capacitance CL Input Pull-up resistance 10 MHz to 30 MHz 10 30MHz to 60 MHz 15 60MHz to 94 MHz 7 RPUE FREQ0 VIL = 0.0 V Power supply current ICC VDD No load capacitance at 27 MHz output ma Power down current Ipd VDD Input clock stopping 4 µ A AC Characteristics (Ta = 40 C to + 85 C, VDD = 3.3 V ± 0.3 V, VSS = 0.0 V) Parameter Symbol Pin Conditions Value Min Typ Max Unit Input frequency fin CKIN MHz Output frequency fout MHz Output slew rate SR Load capacitance 15 pf 0.4 V to 2.4 V V/ns Output clock duty cycle tdcc 1.5 V % Output Rise Time between 20% to 80% 1.3 ns Output Fall Time between 80% to 20% 1.0 ns pf kω 6/14

7 (Continued) Parameter Symbol Pin Conditions (Ta = 40 C to + 85 C, VDD = 3.3 V ± 0.3 V, VSS = 0.0 V) Value Min Typ Max Lock-up time tlk 10.0 MHz to 60 MHz 2 5 ms 60 MHz to 94 MHz 3 8 Cycle-cycle jitter tjc No load capacitance, Ta = + 25 C, VDD = 3.3 V Note : The modulation clock stabilization wait time is required after the power is turned on, the IC recovers from power saving, or after FREQ (frequency range) or ENS (modulation ON/OFF) setting is changed. For the modulation clock stabilization wait time, assign the maximum value for lock-up time. Unit 100 ps-rms <Definition of modulation frequency and number of input clocks per modulation> f (Output frequency) t Modulation wave form fmod (Min) fmod (Max) Clock count nmod (Max) Clock count nmod (Min) t contains the modulation period to realize the efficient EMI reduction. The modulation period fmod depends on the input frequency and changes between fmod (Min) and fmod (Max). Furthermore, the average value of fmod equals the typical value of the electrical characteristics. 7/14

8 OUTPUT CLOCK DUTY CYCLE (tdcc = tb/ta) ta tb 1.5 V INPUT FREQUENCY (fin = 1/tin) tin 0.8 VDD CKIN OUTPUT SLEW RATE (SR) 2.4 V 0.4 V tr tf Note : SR = ( ) /tr, SR = ( ) /tf 8/14

9 MODULATION WAVE FORM ±1.5% modulation rate, Example of center spread output frequency % Frequency at modulation OFF Time 1.5 % fmod 1.0% modulation rate, Example of down spread output frequency Frequency at modulation OFF Time 0.5 % 1.0 % fmod 9/14

10 SPECTRUM EXAMPLE CHARACTERISTICS The condition of the examples of the characteristic is shown as follows: Input frequency = 24 MHz (Output frequency = 24 MHz), use for Power-supply voltage = 3.3 V, None load capacity. Modulation rate = ± 1.5% (center spread). Avg 4 CH B Spectrum 10 db /REF 0 dbm No modulation 8.86 dbm ±1.5% modulation dbm RBW# 1 khz VBW 1 khz ATT 6 db CENTER 20 MHZ SWP s SPAN 4 MHZ 10/14

11 Center spread Spectrum is spread (modulated) by centering on the input frequency. Radiation level 3.0% modulation width 1.5% +1.5% Frequency Input frequency Center spread example of ± 1.5% modulation rate Diagram of CLK spread IC1 CLK IC2 CLK LCD CLK 1107AF MCU SDRAM CLK HDMI-CSI CLK 11/14

12 TDFN COL 2x2 8L package Outline drawing Dimensions Symbol Inches Millimeters Min Max Min Max A A BSC BSC b D BSC 2.00 BSC E BSC 2.00 BSC e BSC 0.50 BSC L /14

13 Typical Application Schematic 13/14

14 Ordering Code Part Number Package Temperature -08-CR 8- pin 2-mm TDFN COL - TAPE & REEL, Green -40 C to +85 C Device Ordering Information -08-CR R = Tape & Reel, T = Tube or Tray O = TSOT23 U = MSOP J=TSOT26 S = SOIC E = TQFP C=TDFN (2X2) COL T = TSSOP L = LQFP A = SSOP U = MSOP V = TVSOP P = PDIP B = BGA D = QSOP Q = QFN X = SC-70 DEVICE PIN COUNT F = LEAD FREE AND RoHS COMPLIANT PART G = GREEN PACKAGE, LEAD FREE, and RoHS PART NUMBER I= Industrial P or n/c = Commercial (-40 C to +85 C ) (0 C to +70 C) A = Clock Generator B = Non PLL based C = EMI Reduction D = DDR support products E = STD Zero Delay Buffer F = Power Management G = Power Management H = Power Management I = Hi Performance J = Reserved Spread Spectrum Device CO.,LTD 14/14