DS1083L PLL WITH CENTER- SPREAD DITHERING CLOCK RATE DETECT CONFIGURATION DECODE AND CONTROL

Transcription

1 Rev ; 5/7 1MHz to 13MHz Spread-Spectrum General Description The is a spread-spectrum clock modulator IC that reduces EMI in high-clock, frequency-based, digital electronic equipment. Using an integrated phase-locked loop (PLL), the accepts an input clock signal in the range of 1MHz to 13MHz and delivers a spread-spectrum modulated output clock signal. The PLL modulates, or dithers, the output clock about the center input frequency at a pin-selectable magnitude. The automatically adjusts the dither rate based on the input clock frequency to maximize the EMI reduction. By dithering the system clock, all the address, data, and timing signals generated from this signal are also dithered so that the measured EMI at the fundamental and harmonic frequencies is greatly reduced. This is accomplished without changing clock rise/fall times or adding the space, weight, design time, and cost associated with mechanical shielding. The is provided in a low-cost, space-saving, -lead thin SOT3 package and operates over a full automotive temperature range of - C to +15 C. Applications LCD Panels for TVs, Desktop Monitors, Notebook and Tablet PCs Automotive Telematics and Infotainment Printers Pin Configuration and Typical Operating Circuit appear at end of data sheet. Features Modulates a 1MHz to 13MHz Clock with Center Spread-Spectrum Dithering Selectable Spread-Spectrum Modulation Magnitudes of: ±.5% ±1% ±1.5% ±% Low 75ps Cycle-to-Cycle Jitter Automatic Dither Cycle Rate Adjustment to Maximize EMI Reduction Low Cost Low Power Consumption 3.3V Single Voltage Supply - C to +15 C Operating Temperature Range Small -Lead Thin SOT3 Package Ordering Information PART TEMP RANGE PIN-PACKAGE R+T - C to +15 C Thin SOT3 +Denotes a lead-free package. T = Tape and reel. Block Diagram f IN = 1MHz TO 13MHz PLL WITH CENTER- SPREAD DITHERING f = 1MHz to 13MHz (DITHERED) VCC SMSEL1 SMSEL R PU R PU CLOCK RATE DETECT CONFIGURATION DECODE AND CONTROL Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1--9-, or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS Voltage Range on VCC Relative to...-.5v to +3.3V Voltage Range on Any Lead Relative to...-.5v to ( +.5V), not to exceed +3.3V Operating Temperature Range...- C to +15 C Storage Temperature Range C to +15 C Soldering Temperature...Refer to the IPC/JEDEC J-STD- Specification. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. RECOMMENDED OPERATING CONDITIONS (TA = - C to +15 C, unless otherwise noted.) Supply Voltage (Note 1) V SMSEL1/SMSEL Input Logic 1 V IH.7 x x SMSEL1/SMSEL Input Logic V IL -.3 f < MHz 15 Load C L MHz f < 13MHz 7 Frequency f IN 1 13 MHz Duty Cycle f INDC % Power-Up Time t PV to MIN ms V V pf DC ELECTRICAL CHARACTERISTICS ( = +3.V to +3.V, T A = - C to +15 C, unless otherwise noted.) Supply Current I CC C L = 7pF, f IN = 13MHz 15 ma SMSEL1/SMSEL Pullup Resistance R PU T A = +5 C 1 1 k SMSEL1/SMSEL Input Leakage I IL V < V IN < ± μa Low-Level Output Voltage () V OL I OL = ma. V High-Level Output Voltage () V OH I OH = -ma. V AC ELECTRICAL CHARACTERISTICS ( = +3.V to +3.V, T A = - C to +15 C, unless otherwise noted.) Duty Cycle f DC Measured at / % Rise Time t R C L = 7pF 1 ns Fall Time t F C L = 7pF 1 ns Peak Cycle-to-Cycle Jitter t J T A = - C to +5 C, 1, cycles 75 ps Note 1: All voltages referenced to ground. Currents into the IC are positive and currents out of the IC are negative.

3 (T A = +5 C, unless otherwise noted.) SUPPLY CURRENT vs. SUPPLY VOLTAGE 1 = 13MHz 1 = 1MHz toc1 1 1 SUPPLY CURRENT vs. TEMPERATURE = 13MHz = 1MHz Typical Operating Characteristics toc SUPPLY CURRENT vs. FREQUENCY 1 1 = 3.V = 3.V toc SUPPLY VOLTAGE (V) TEMPERATURE ( C) FREQUENCY (MHz) DUTY CYCLE (%) DUTY CYCLE vs. TEMPERATURE toc DUTY CYCLE (%) DUTY CYCLE vs. SUPPLY VOLTAGE toc5 ATTENUATION (db) SPECTRUM ATTENUATION vs. FREQUENCY AT DIFFERENT DITHER AMPLITUDES ±1% ±1.5% ±%.5% f OUT = MHz 3dB.5dB db toc - - TEMPERATURE ( C) SUPPLY VOLTAGE (V) f OUT = MHz RBW = 1kHz CENTER DITHER FREQUENCY (MHz) 3

4 PIN NAME DESCRIPTION 1 Clock Input. 1MHz to 13MHz clock input (f IN ). Ground 3 SMSEL 5 SMSEL1 VCC Supply Voltage Pin Description Spread-Spectrum Clock Output. Outputs a center-dithered spread-spectrum version of the clock input at. Spread-Spectrum Magnitude Select Inputs. These digital inputs select the desired spread-spectrum magnitude as shown in the table below. Both inputs contain pullup resistors (R PU ) to. SMSEL SMSEL1 MAGNITUDE SELECTED (%) ± 1 ±1.5 1 ±1 1 1 ±.5 Detailed Description The modulates an input clock to provide a center-dithered spread-spectrum output. A 1MHz to 13MHz clock is applied to the pin. The PLL dithers the output clock about its center frequency at a user-selectable magnitude. The user is required to cycle power to the device each time there is a change in the input frequency, for the PLL to lock correctly. This ensures proper output frequency and dither rate. The desired spread-spectrum magnitude is selected using input pins SMSEL1 and SMSEL (see the Pin Description for details). The is capable of generating spread-spectrum clocks from 1MHz to 13MHz. Dither-Rate Selection The output spread-spectrum dither rate is automatically adjusted depending on the input frequency, to maximize EMI reduction. The dither cycle rate is: f IN /51, if f IN is between 1MHz and 33MHz f IN /1, if f IN is between 33MHz and MHz f IN /, if f IN is between MHz and 13MHz On power-up, the output clock () remains threestated until it reaches a stable frequency (f ). The dither rate is selected by sampling the input clock at power-up. Applications Information Power-Supply Decoupling To achieve best results, it is highly recommended that a decoupling capacitor is used on the IC power-supply pins. Typical values of decoupling capacitors are.1µf and.1µf. Use a high-quality, ceramic, surfacemount capacitor, and mount it as close as possible to the VCC and pins of the IC to minimize lead inductance. Chip Information SUBSTRATE CONNECTED TO GROUND

5 f IN + (.5%, 1%, 1.5%, OR % OF f IN ) f IN f IN - (.5%, 1%, 1.5%, OR % OF f IN ) f 1 DITHER CYCLE RATE* IF DITHER AMOUNT = % DITHER AMOUNT (±.5%, ±1%, ±1.5%, OR ±%) *DITHER CYCLE RATE = f IN /51, IF f IN = 1MHz TO 33MHz f IN /1, IF f IN = 33MHz TO MHz f IN /, IF f IN = MHz TO 13MHz TIME Figure 1. Spread-Spectrum Frequency Modulation Typical Operating Circuit f IN = 1MHz TO 13MHz VCC SMSEL1 DECOUPLING CAPACITOR f DITHERED SMSEL NOTE: IN THE ABOVE CONFIGURATION WITH SMSEL1 CONNECTED TO VCC AND SMSEL CONNECTED TO, THE DEVICE WILL HAVE A SPREAD-SPECTRUM MAGNITUDE OF ±1.5%. TOP VIEW Pin Configuration Package Information For the latest package outline information, go to VCC PACKAGE TYPE DOCUMENT NO. Thin SOT SMSEL1 3 SMSEL THIN SOT3 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 1 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.