Rev 0; 4/07 20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels The DS1081L 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 DS1081L accepts an input clock signal in the range of 20MHz to 134MHz 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 and dither rate, allowing direct EMI control and optimization. In addition, through an enable pin the dithering can be enabled or disabled for easy comparison of system performance during EMI testing. This same input pin also allows the DS1081L output to be tri-stated. 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 DS1081L is provided in an 8-pin TSSOP package and operates over a full automotive temperature range of -40°C to +125°C. Features ♦ Modulates a 20MHz to 134MHz Clock with Center Spread-Spectrum Dithering ♦ Selectable Spread-Spectrum Modulation Magnitudes of: ±0.5% ±1.0% ±1.5% ±2.0% ♦ Low 75ps Cycle-to-Cycle Jitter ♦ Spread-Spectrum Disable Mode ♦ Pin Compatible with Alliance/PulseCore Semiconductor P2040 Series Devices ♦ Clock Output Disable ♦ Low Cost ♦ Low Power Consumption ♦ 3.3V Single Voltage Supply ♦ -40°C to +125°C Temperature Range ♦ Small 8-Pin TSSOP Package Ordering Information Applications LCD Panels for TVs, Desktop Monitors, and Notebook and Tablet PCs Automotive Telematics and Infotainment Printers Pin Configuration and Typical Operating Circuit appear at end of data sheet. PART TEMP RANGE -40°C to +125°C 8 TSSOP DS1081LE+T -40°C to +125°C 8 TSSOP +Denotes lead-free package. T Denotes tape-and-reel. Pin Configuration Block Diagram VCC DS1081L CLKIN fIN = 20MHz TO 134MHz TOP VIEW VCC PLL WITH CENTERDITHERED SPREAD SPECTRUM SSO fSSO = 20MHz to 134MHz (DITHERED) ENABLE LOGIC SSEN CLKIN 1 8 VCC SMSEL1 2 7 CRSEL SMSEL2 3 6 SSO 5 SSEN DS1081L GND 4 CRSEL SMSEL1 SMSEL2 PIN-PACKAGE DS1081LE+ CONFIGURATION DECODE AND CONTROL GND TSSOP (4.40mm) ______________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 DS1081L General Description DS1081L 20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels ABSOLUTE MAXIMUM RATINGS Voltage Range on VCC Relative to GND .............-0.5V to +3.63V Voltage Range on Any Lead Relative to GND ................-0.5V to (VCC + 0.5V), not to exceed +3.63V Operating Temperature Range .........................-40°C to +125°C Storage Temperature Range .............................-55°C to +125°C Soldering Temperature...................See J-STD-020 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 = -40°C to +125°C, unless otherwise noted.) PARAMETER SYMBOL MAX UNITS 3.0 3.6 V VIH 0.8 x VCC VCC + 0.3 V VIL -0.3 0.2 x VCC V μA Supply Voltage VCC Input Logic 1 Input Logic 0 Input Logic Float (SSEN, CRSEL) SSO Load VFLOAT CL CONDITIONS (Note 1) MIN TYP 0V < VIN < VCC ±1 SSO < 80MHz 15 80MHz SSO < 134MHz 7 pF CLKIN Frequency f IN 20 134 MHz CLKIN Duty Cycle f INDC 40 60 % MAX UNITS 15 mA -1 +1 μA -100 +100 μA -1 +1 μA 0.4 V DC ELECTRICAL CHARACTERISTICS (VCC = +3.0V to +3.6V, TA = -40°C to +125°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP CL = 7pF f IN = 134MHz Supply Current ICC SMSEL1/SMSEL2/CLKIN Input Leakage I IL:1 CRSEL/SSEN Input Leakage IIL:2 0V < VIN < VCC 0V < VIN < VCC Output Leakage (SSO) I OZ SSEN = float Low-Level Output Voltage (SSO) VOL I OL = 4mA High-Level Output Voltage (SSO) VOH I OH = -4mA 2.4 V AC ELECTRICAL CHARACTERISTICS (VCC = +3.0V to +3.6V, TA = -40°C to +125°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS TYP UNITS 60 % SSO Rise Time tR CL = 7pF 1 ns SSO Fall Time tF CL = 7pF 1 ns Peak Cycle-to-Cycle Jitter tJ TA = -40°C to +85°C, 10,000 cycles 75 ps t POR 40 MAX f SSODC Power-Up Time Measured at VCC/2 MIN SSO Duty Cycle (Note 2) Note 1: All voltages referenced to ground. Currents into the IC are positive and out of the IC are negative. Note 2: Time between power applied to device and stable output. 2 _____________________________________________________________________ 50 ms 20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels SUPPLY CURRENT vs. SUPPLY VOLTAGE 8 CLKIN = 20MHz 6 4 3.1 3.2 3.3 3.4 3.5 CLKIN = 33MHz 6 4 VCC = 3.6V 10 8 VCC = 3.0V 6 4 2 0 -40 -20 3.6 0 20 40 60 80 100 120 20 36 56 76 96 116 134 FREQUENCY (MHz) DUTY CYCLE vs. TEMPERATURE DUTY CYCLE vs. SUPPLY VOLTAGE SPECTRUM ATTENUATION vs. FREQUENCY AT DIFFERENT DITHER AMPLITUDES 60 56 52 50 48 52 50 48 46 44 44 42 42 0 20 40 60 80 TEMPERATURE (°C) 100 120 fOUT = 40MHz 0.5% 3dB 6dB 4.5dB fOUT = 40MHz RBW = 120KHz CENTER DITHER 40 -40 -20 ±1% ±1.5% ±2% 54 46 40 CLKIN = 66MHz 56 DUTY CYCLE (%) 54 58 ATTENUATION (dB) CLKIN = 66MHz DS1081L toc06 TEMPERATURE (°C) DS1081L toc05 SUPPLY VOLTAGE (V) DS1081L toc04 3.0 DUTY CYCLE (%) 8 0 0 58 CLKIN = 66MHz 12 2 2 60 10 DS1081L toc03 CLKIN = 66MHz CLKIN = 134MHz SUPPLY CURRENT (mA) 10 12 14 DS1081L toc02 CLKIN = 134MHz DS1081L toc01 12 SUPPLY CURRENT vs. FREQUENCY SUPPLY CURRENT vs. TEMPERATURE 14 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 14 3.0 3.1 3.2 3.3 3.4 SUPPLY VOLTAGE (V) 3.5 3.6 FREQUENCY (MHz) _____________________________________________________________________ 3 DS1081L Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) 20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels DS1081L Pin Description PIN NAME 1 CLKIN 2 SMSEL2 FUNCTION Clock Input. 20MHz to 134MHz clock input (fIN). Spread-Spectrum Magnitude Select Inputs. These digital inputs select the desired spread-spectrum magnitude as shown in the table below. SMSEL2 SMSEL1 MAGNITUDE SELECTED 0 0 ±2.0% 0 1 1 0 ±1.5% ±1.0% 1 1 ±0.5% 3 SMSEL1 4 GND Ground 5 SSEN Spread-Spectrum Enable. Three-level input to enable/disable spread-spectrum and to tri-state the output. 0 = Power-up/spread-spectrum enabled. Float = SSO tri-stated. 1 = Power-up/spread-spectrum disabled (not a bypass mode). 6 SSO Spread-Spectrum Clock Output. Outputs a center-dithered spread-spectrum version of the clock input at CLKIN. Clock Range and Dither Rate Select. Three-level input that determines the dither rate. See the Detailed Description section for details. 7 CRSEL 8 VCC CRSEL CLKIN RANGE DITHER RATE 0 66MHz to 134MHz f IN/2048 Float 33MHz to 80MHz f IN/1024 1 20MHz to 38MHz f IN/512 Supply Voltage Detailed Description The DS1081L modulates an input clock to generate a center-dithered spread-spectrum output. A 20MHz to 134MHz clock is applied to the CLKIN pin. An internal PLL dithers the output clock about its center frequency at a user-selectable magnitude. Spread-Spectrum Dither Magnitude The DS1081L can generate dither magnitudes up to ±2%. The desired magnitude is selected using input pins SMSEL1 and SMSEL2 as shown in Table 1. Table 1. 4 SMSEL2 SMSEL1 MAGNITUDE 0 0 ±2.0% 0 1 ±1.5% 1 0 ±1.0% 1 1 ±0.5% Spread-Spectrum Dither Rate The output spread-spectrum dither rate is determined by the input frequency to maximize EMI reduction and to ensure that the dither rate is always above the audio frequency range. The user must configure CRSEL, based on Table 2, depending on the input frequency (fIN) so that the appropriate dither rate is programmed. Table 2. CRSEL CLKIN RANGE DITHER RATE 0 66MHz to 134MHz f IN/2048 Float 33MHz to 80MHz f IN/1024 1 20MHz to 38MHz f IN/512 _____________________________________________________________________ 20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels 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 0.01µF and 0.1µF. Use a high-quality, ceramic, surface-mount capacitor, and mount it as close as possible to the VCC and GND pins of the IC to minimize lead inductance. IF SSEN = 1 fIN + (0.5%, 1.0%, 1.5%, OR 2.0% OF fIN) DITHER AMOUNT (±0.5%, ±1.0%, ±1.5%, OR ±2.0%) fIN fIN - (0.5%, 1.0%, 1.5%, OR 2.0% OF fIN) 1 fSSO DITHER CYCLE RATE TIME CLKIN RANGE (MHz) 66 TO 134 33 TO 80 20 TO 38 DITHER RATE fIN/2048 fIN/1024 fIN/512 Figure 1. DS1081L Spread-Spectrum Frequency Modulation Typical Operating Circuit VCC fIN = 20MHz TO 134MHz VCC CLKIN DECOUPLING CAPACITOR CRSEL SMSEL1 DS1081L SSO fSSO SMSEL2 SSEN GND DITHERED NOTE: IN THE ABOVE CONFIGURATION WITH SMSEL1, SMSEL2, AND SSEN CONNECTED TO GND AS WELL AS CRSEL CONNECTED TO VCC AND SSEN CONNECTED TO GND, THE DEVICE IS CONFIGURED WITH A SPREAD-SPECTRUM MAGNITUDE OF ±2.0%, AND ALLOWS A CLKIN BETWEEN 20MHz and 38MHz. Package Information For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo. 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, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 5 © 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. is a registered trademark of Dallas Semiconductor Corporation. DS1081L Application Information Spread-Spectrum Enable On power-up, the output clock (SSO) remains tri-stated until the internal PLL reaches a stable frequency. The SSEN input can be used to disable the spread-spectrum modulation and to tri-state the SSO output. If the SSEN pin is pulled high, the spread-spectrum modulation is turned off, but the device still uses the internal PLL to generate the clock signal at SSO. If the SSEN pin is floated, the output will be tri-stated.