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Rev 0; 11/07
20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels
General Description
The DS1181L 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 DS1181L 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, 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 DS1181L output to be three-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 DS1181L is provided in an 8-pin TSSOP package and operates over a full automotive temperature range of -40C to +125C.
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 -40C to +125C Temperature Range Small 8-Pin TSSOP Package
DS1181L
Applications
LCD Panels for TVs, Desktop Monitors, and Notebook and Tablet PCs Automotive Telematics and Infotainment Printers
Typical Operating Circuit appears at end of data sheet.
PART DS1181LE+ DS1181LE+T
Ordering Information
TEMP RANGE -40C to +125C -40C to +125C PIN-PACKAGE 8 TSSOP 8 TSSOP
+Denotes a lead-free package. T = Tape and reel.
Block Diagram
VCC
Pin Configuration
DS1181L
CLKIN fIN = 20MHz TO 134MHz PLL WITH CENTERDITHERED SPREADSPECTRUM
VCC SSO fSSO = 20MHz to 134MHz (DITHERED)
TOP VIEW +
CLKIN SMSEL1 SMSEL2 1 2 3 8 7 VCC CRSEL SSO SSEN
ENABLE LOGIC CRSEL SMSEL1 SMSEL2
SSEN
DS1181L
6 5
GND 4
CONFIGURATION DECODE AND CONTROL GND
TSSOP
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels DS1181L
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 .........................-40C to +125C Storage Temperature Range .............................-55C to +125C 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 = -40C to +125C, unless otherwise noted.)
PARAMETER Supply Voltage Input Logic 1 Input Logic 0 Input Logic Float (SSEN, CRSEL) SSO Load CLKIN Frequency CLKIN Duty Cycle SYMBOL VCC VIH VIL IFLOAT CL f IN f INDC 0V < VIN < VCC SSO < 80MHz 80MHz SSO < 134MHz 20 40 (Note 1) CONDITIONS MIN 3.0 0.8 x VCC -0.3 TYP MAX 3.6 VCC + 0.3 0.2 x VCC 1 15 7 134 60 UNITS V V V A pF MHz %
DC ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to +3.6V, TA = -40C to +125C, unless otherwise noted.)
PARAMETER Supply Current SMSEL1/SMSEL2/CLKIN Input Leakage CRSEL/SSEN Input Leakage Output Leakage (SSO) Low-Level Output Voltage (SSO) High-Level Output Voltage (SSO) SYMBOL ICC I IL:1 IIL:2 I OZ VOL VOH CONDITIONS CL = 7pF, f IN = 134MHz 0V < VIN < VCC 0V < VIN < VCC SSEN = float I OL = 4mA I OH = -4mA 2.4 -1 -100 -1 MIN TYP MAX 18 +1 +100 +1 0.4 UNITS mA A A A V V
AC ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to +3.6V, TA = -40C to +125C, unless otherwise noted.)
PARAMETER SSO Duty Cycle SSO Rise Time SSO Fall Time Peak Cycle-to-Cycle Jitter Power-Up Time SYMBOL f SSODC tR tF tJ t POR CL = 7pF CL = 7pF TA = -40C to +85C, 10,000 cycles (Note 2) CONDITIONS Measured at VCC/2 MIN 40 1 1 75 50 TYP MAX 60 UNITS % ns ns ps ms
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 _______________________________________________________________________________________
20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
DS1181L
SUPPLY CURRENT vs. SUPPLY VOLTAGE
DS1181L toc01
SUPPLY CURRENT vs. TEMPERATURE
CLKIN = 134MHz 10 CLKIN = 66MHz 8 ICC (mA) 8 CLKIN = 20MHz ICC (mA)
DS1181L toc02
SUPPLY CURRENT vs. FREQUENCY
DS1181L toc03
12 CLKIN = 134MHz 10 CLKIN = 66MHz 8 ICC (mA) 6 4 2 CL = 7pF 0 3.0 3.1 3.2 3.3 VCC (V) 3.4 3.5 CLKIN = 20MHz
12
12 10 VCC = 3.6V VCC = 3.0V 6 4 2
6 4 2
CL = 7pF 0 3.6 -40 10 60 110 TEMPERATURE (C) 0 20 40 60 80
CL = 7pF 100 120
FREQUENCY (MHz)
DUTY CYCLE vs. SUPPLY VOLTAGE
DS1181L toc04
DUTY CYCLE vs. TEMPERATURE
DS1181L toc05
SPECTRUM ATTENUATION vs. FREQUENCY AT DIFFERENT DITHER AMPLITUDES
fOUT = 72MHz 0.5% 1% 1.5% 2% ATTENUATION (dB) 10dB 13dB
DS1181L toc06
60 58 56 DUTY CYCLE (%) 54 52 50 48 46 44 42 40 3.0 3.1 3.2 3.3 VCC (V) 3.4 3.5 CLKIN = 72MHz
60 58 56 DUTY CYCLE (%) 54 52 50 48 46 44 42 40 CLKIN = 72MHz
15dB 17dB
RBW = 120KHz CENTER DITHER -40 10 60 110 FREQUENCY (MHz)
3.6
TEMPERATURE (C)
_______________________________________________________________________________________
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20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels DS1181L
Pin Description
PIN 1 NAME CLKIN 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 0 0 3 SMSEL2 1 1 4 GND Ground Spread-Spectrum Enable. Three-level input to enable/disable spread-spectrum and to three-state the output. 0 = Power-up/spread-spectrum enabled. Float = SSO three-stated. 1 = Power-up/spread-spectrum disabled (not a bypass mode). 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 CRSEL 0 Float 1 8 VCC Supply Voltage CLKIN RANGE (MHz) 66 to 134 33 to 80 20 to 38 f IN/832 DITHER RATE SMSEL1 0 1 0 1 MAGNITUDE SELECTED (%) 2.0 1.5 1.0 0.5
2
SMSEL1
5
SSEN
6
SSO
Detailed Description
The DS1181L 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 Rate
The output spread-spectrum dither rate is fixed at fIN/832.
Table 2. Dither Rate
CRSEL 0 Float 1 CLKIN RANGE (MHz) 66 to 134 33 to 80 20 to 38 f IN/832 DITHER RATE
Spread-Spectrum Dither Magnitude
The DS1181L 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. Dither Magnitude
SMSEL2 0 0 1 1 SMSEL1 0 1 0 1 MAGNITUDE SELECTED (%) 2.0 1.5 1.0 0.5
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20MHz to 134MHz Spread-Spectrum Clock Modulator for LCD Panels
Spread-Spectrum Enable
On power-up, the output clock (SSO) remains three-stated until the internal PLL reaches a stable frequency. The SSEN input can be used to disable the spread-spectrum modulation and to three-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 is three-stated.
Application 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 0.01F and 0.1F. 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
DS1181L
fIN + (0.5%, 1.0%, 1.5%, OR 2.0% OF fIN) fIN fIN - (0.5%, 1.0%, 1.5%, OR 2.0% OF fIN) DITHER AMOUNT (0.5%, 1.0%, 1.5%, OR 2.0%)
1 fSSO DITHER CYCLE RATE
TIME CLKIN RANGE (MHz) 20 TO 134 DITHER RATE fIN/832
Figure 1. DS1181L Spread-Spectrum Frequency Modulation
Typical Operating Circuit
VCC fIN = 20MHz TO 134MHz VCC CRSEL SMSEL1 SMSEL2 GND SSEN DITHERED DECOUPLING CAPACITOR fSSO
CLKIN
DS1181L
SSO
NOTE: IN THE ABOVE CONFIGURATION WITH SMSEL1, SMSEL2, AND SSEN CONNECTED TO GND AS WELL AS CRSEL CONNECTED TO VCC, 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.) PACKAGE TYPE 8 TSSOP DOCUMENT NO. 56-G2021-000
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
(c) 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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