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DS1081LE+T
Spread-Spectrum Clock Modulator for LCD Panels
DS1081L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
General DescriptionThe 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 mod-
ulated 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 test-
ing. This same input pin also allows the DS1081L 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 asso-
ciated 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.
ApplicationsLCD Panels for TVs, Desktop Monitors, and
Notebook and Tablet PCs
Automotive Telematics and Infotainment
Printers
FeaturesModulates a 20MHz to 134MHz Clock with Center
Spread-Spectrum DitheringSelectable Spread-Spectrum Modulation
Magnitudes of:
±0.5%
±1.0%
±1.5%
±2.0%Low 75ps Cycle-to-Cycle JitterSpread-Spectrum Disable ModePin Compatible with Alliance/PulseCore
Semiconductor P2040 Series DevicesClock Output DisableLow Power Consumption3.3V Single Voltage Supply-40°C to +125°C Temperature RangeSmall 8-Pin TSSOP Package19-6013; Rev 1; 10/11
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Ordering Information
PARTTEMP RANGEPIN-PACKAGEDS1081LE+-40°C to +125°C8 TSSOP
DS1081LE+T-40°C to +125°C8 TSSOP
Block DiagramGND
SSOPLL WITH CENTER-
DITHERED
SPREAD
SPECTRUM
CONFIGURATION
DECODE AND
CONTROL
SMSEL1
CLKIN
SMSEL2
fSSO = 20MHz to
134MHz (DITHERED)
VCC
VCC
fIN = 20MHz TO
134MHz
CRSEL
SSENENABLE
LOGICDS1081L
Typical Operating Circuit appears at end of data sheet.SSO
GNDCRSELSMSEL1
SMSEL2
CLKIN
TOP VIEW
VCC
SSEN
DS1081L
Pin Configuration
DS1081L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING CONDITIONS(TA= -40°C to +125°C, unless otherwise noted.)
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.
Voltage Range on VCCRelative to GND.............-0.5V to +3.63V
Voltage Range on Any Pin Relative
to GND................-0.5V to (VCC+ 0.5V), not to exceed +3.63V
Operating Temperature Range.........................-40°C to +125°C
Continuous Power Dissipation (TA= +70°C)
TSSOP (derate 8.1mW/°C above +70°C)..................646.7mW
Storage Temperature Range.............................-55°C to +125°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow).......................................+260°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSupply Voltage VCC (Note 1) 3.0 3.6 V
Input Logic 1 VIH0.8 x
VCC
VCC +
0.3 V
Input Logic 0 VIL -0.3 0.2 x
VCCV
Input Logic Open (SSEN, CRSEL) IOPEN0V < (Voltage applied to SSEN or
CRSEL) < VCC ±1 μA
SSO < 80MHz 15 SSO Load CL
80MHz SSO< 134MHz 7
pF
CLKIN Frequency fIN 20 134 MHz
CLKIN Duty Cycle fINDC 40 60 %
DC ELECTRICAL CHARACTERISTICS(VCC= +3.0V to +3.6V, TA= -40°C to +125°C, unless otherwise noted.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSupply Current ICCCL = 7pF
fIN = 134MHz 15 mA
SMSEL1/SMSEL2/CLKIN Input Leakage IIL:1 0V < VIN < VCC -1 +1 μA
CRSEL/SSEN Input Leakage IIL:2 0V < VIN < VCC -100 +100 μA
Output Leakage (SSO) IOZSSEN = open -1 +1 μA
Low-Level Output Voltage (SSO) VOL IOL = 4mA 0.4 V
High-Level Output Voltage (SSO) VOH IOH = -4mA 2.4 V
AC ELECTRICAL CHARACTERISTICS(VCC= +3.0V to +3.6V, TA= -40°C to +125°C, unless otherwise noted.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSSO Duty Cycle fSSODC Measured at VCC/2 40 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
Power-Up Time tPOR (Note 2) 50 ms
Note 1:All voltages referenced to ground. Currents into the IC are positive and out of the IC are negative.
DS1081L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
Typical Operating Characteristics(TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGEDS1081L toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
CLKIN = 134MHz
CLKIN = 20MHz
CLKIN = 66MHz
SUPPLY CURRENT vs. TEMPERATUREDS1081L toc02
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
CLKIN = 134MHz
CLKIN = 33MHz
CLKIN = 66MHz
SUPPLY CURRENT vs. FREQUENCY
DS1081L toc03
FREQUENCY (MHz)
SUPPLY CURRENT (mA)
VCC = 3.6V
VCC = 3.0V
DUTY CYCLE vs. TEMPERATUREDS1081L toc04
TEMPERATURE (°C)
DUTY CYCLE (%)
CLKIN = 66MHz
DUTY CYCLE vs. SUPPLY VOLTAGEDS1081L toc05
SUPPLY VOLTAGE (V)
DUTY CYCLE (%)
CLKIN = 66MHz
SPECTRUM ATTENUATION vs. FREQUENCY
AT DIFFERENT DITHER AMPLITUDESDS1081L toc06
FREQUENCY (MHz)
ATTENUATION (dB)
fOUT = 40MHz
±2%
±1.5%
0.5%
6dB
4.5dB
3dB
±1%
fOUT = 40MHz
RBW = 120KHz
CENTER DITHER
DS1081L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
Detailed DescriptionThe 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 MagnitudeThe DS1081L can generate dither magnitudes up to
±2%. The desired magnitude is selected using input pins
SMSEL1 and SMSEL2 as shown in Table 1.
Spread-Spectrum Dither RateThe 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.
Pin Description
PIN NAME FUNCTION CLKIN 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 2 SMSEL1
0 0 ±2.0%
0 1 ±1.5%
1 0 ±1.0% 3SMSEL2
1 1 ±0.5% GND GroundSSEN
Spread-Spectrum Enable. Three-level input to enable/disable spread-spectrum and to three-state the
output.
0 = Power-up/spread-spectrum enabled.
Open = SSO three-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.
CRSELCLKIN RANGEDITHER RATE66MHz to 134MHzfIN/2048
Open 33MHz to 80MHz fIN/1024
7 CRSEL
1 20MHz to 38MHz fIN/512 VCCSupply Voltage
CRSEL CLKIN RANGE DITHER RATE 0 66MHz to 134MHz fIN/2048
Open 33MHz to 80MHz fIN/1024
1 20MHz to 38MHz fIN/512
Table 2. Spread-Spectrum Dither Rate
SMSEL2SMSEL1MAGNITUDE±2.0%±1.5%±1.0%±0.5%
Table 1. Spread-Spectrum Dither Magnitude
DS1081L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
Spread-Spectrum EnableOn power-up, the output clock (SSO) remains three-stat-
ed until the internal PLL reaches a stable frequency. The
SSENinput can be used to disable the spread-spec-
trum modulation and to three-state the SSO output. If the
SSENpin is pulled high, the spread-spectrum modula-
tion is turned off, but the device still uses the internal
PLL to generate the clock signal at SSO. If the SSENpin
is open, the output is three-stated.
Applications Information
Power-Supply DecouplingTo 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.
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)
fSSO
TIME
DITHER CYCLE
RATE
DITHER AMOUNT
(±0.5%, ±1.0%, ±1.5%, OR ±2.0%)
CLKIN RANGE (MHz)DITHER RATE
66 TO 134fIN/2048
33 TO 80fIN/1024
20 TO 38fIN/512
IF SSEN = 1
Figure 1. Spread-Spectrum Frequency Modulation
CLKIN
SMSEL1
SMSEL2
GND
CRSEL
VCC
DECOUPLING
CAPACITOR
VCC
SSO
fIN = 20MHz TO
134MHz
NOTE: IN THE ABOVE CONFIGURATION WITH SMSEL1, SMSEL2, AND SSEN CONNECTED TO GND AS WELL ASCRSEL 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.
fSSO
DITHEREDSSEN
DS1081L
ypical Operating Circuit
PACKAGE TYPEPACKAGE CODEOUTLINE NO.LAND PATTERN NO.21-017590-0248
Package InformationFor the latest package outline information and land patterns (footprints), go to /packages. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains
to the package regardless of RoHS status.
DS1081L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD PanelsMaxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
Revision History
REVISION
NUMBER
REVISION
DATEDESCRIPTIONPAGES
CHANGED 0 4/07 Initial release —
1 10/11
Updated the Absolute Maximum Ratings,Recommended Operating Conditions, and
DC Electrical Characteristics; corrected pin number error in the Pin Description; added
the Package Information table
2, 4, 5