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 mod-
ulated 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 dither-
ing 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 asso-
ciated with mechanical shielding.
The DS1181L is provided in an 8-pin TSSOP package
and operates over a full automotive temperature range
of -40°C to +125°C.
Applications
LCD Panels for TVs, Desktop Monitors, and
Notebook and Tablet PCs
Automotive Telematics and Infotainment
Printers
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
DS1181L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
________________________________________________________________
Maxim Integrated Products
1
Rev 1; 8/08
+
Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Ordering Information
PART TEMP RANGE PIN-PACKAGE
DS1181LE+ -40°C to +125°C 8 TSSOP
DS1181LE+T -40°C to +125°C 8 TSSOP
Block Diagram
GND
SSO
PLL WITH CENTER-
DITHERED
SPREAD-
SPECTRUM
CONFIGURATION
DECODE AND
CONTROL
SMSEL1
CLKIN
SMSEL2
fSSO = 20MHz to
134MHz (DITHERED)
VCC
VCC
fIN = 20MHz TO
134MHz
CRSEL
SSEN
ENABLE
LOGIC
DS1181L
SSO
GND
1
2
8
7 CRSELSMSEL1
SMSEL2
CLKIN
TSSOP
TOP VIEW
3
4
6
5
VCC
SSEN
DS1181L
+
Pin Configuration
For information on other Maxim products, visit Maxim’s website at www.maxim-ic.com.
Typical Operating Circuit appears at end of data sheet.
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 VCC Relative to GND ...............-0.5V to +4.3V
Voltage Range on Any Lead Relative
to GND ..................-0.5V to (VCC + 0.5V), not to exceed +4.3V
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature...................See J-STD-020 Specification
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage VCC (Note 1) 3.0 3.6 V
Input Logic 1 VIH 0.8 x
VCC
VCC +
0.3 V
Input Logic 0 VIL -0.3 0.2 x
VCC V
Input Logic Float (SSEN, CRSEL) IFLOAT 0V < VIN < VCC ±1 μA
SSO < 80MHz 15
SSO Load CL80MHz 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.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Current ICC CL = 7pF,
fIN = 134MHz 18 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) IOZ SSEN = float -1 +1 μA
Low-Level Output Voltage (SSO) VOL I
OL = 4mA 0.4 V
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 MIN TYP MAX UNITS
SSO Duty Cycle fSSODC Measured at VCC/2 40 60 %
SSO Rise Time tR C
L = 7pF 1 ns
SSO Fall Time tF C
L = 7pF 1 ns
Peak Cycle-to-Cycle Jitter tJ T
A = -40°C to +85°C, 10,000 cycles 75 ps
Power-Up Time tPOR (Note 2) 50 ms
DS1181L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
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.
DS1181L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
_______________________________________________________________________________________ 3
SUPPLY CURRENT vs. SUPPLY VOLTAGE
DS1181L toc01
VCC (V)
ICC (mA)
3.53.43.33.23.1
2
4
6
8
10
12
0
3.0 3.6
CLKIN = 134MHz
CLKIN = 20MHz
CL = 7pF
CLKIN = 66MHz
SUPPLY CURRENT vs. TEMPERATURE
DS1181L toc02
TEMPERATURE (°C)
ICC (mA)
1106010
2
4
6
8
10
12
0
-40
CLKIN = 134MHz
CLKIN = 20MHz
CL = 7pF
CLKIN = 66MHz
SUPPLY CURRENT vs. FREQUENCY
DS1181L toc03
FREQUENCY (MHz)
ICC (mA)
120100806040
2
4
6
8
10
12
0
20
CL = 7pF
VCC = 3.6V
VCC = 3.0V
DUTY CYCLE vs. SUPPLY VOLTAGE
DS1181L toc04
VCC (V)
DUTY CYCLE (%)
3.53.43.33.23.1
42
44
46
48
50
52
54
56
58
60
40
3.0 3.6
CLKIN = 72MHz
DUTY CYCLE vs. TEMPERATURE
DS1181L toc05
TEMPERATURE (°C)
DUTY CYCLE (%)
1106010
42
44
46
48
50
52
54
56
58
60
40
-40
CLKIN = 72MHz
SPECTRUM ATTENUATION vs. FREQUENCY A
T
DIFFERENT DITHER AMPLITUDES
DS1181L toc06
FREQUENCY (MHz)
ATTENUATION (dB)
fOUT = 72MHz
RBW = 120KHz
CENTER DITHER
±2%
±1.5%
±1%
0.5%
10dB 13dB 15dB 17dB
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 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.
Spread-Spectrum Dither Rate
The output spread-spectrum dither rate is fixed at
fIN/832.
DS1181L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
4 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1CLKIN 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
4GND Ground
5SSEN
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).
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.
CRSEL CLKIN RANGE (MHz) DITHER RATE
0 66 to 134
Float 33 to 80
7 CRSEL
1 20 to 38
fIN/832
8VCC Supply Voltage
CRSEL CLKIN RANGE
(MHz) DITHER RATE
0 66 to 134
Float 33 to 80
1 20 to 38
fIN/832
Table 2. Dither Rate
SMSEL2 SMSEL1
MAGNITUDE
SELECTED (%)
0 0 ±2.0
0 1 ±1.5
1 0 ±1.0
1 1 ±0.5
Table 1. Dither Magnitude
DS1181L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
Spread-Spectrum Enable
On power-up, the output clock (SSO) remains three-stat-
ed until the internal PLL reaches a stable frequency. The
SSEN input can be used to disable the spread-spec-
trum modulation and to three-state the SSO output. If the
SSEN pin 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 SSEN pin
is floated, the output is three-stated.
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 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
1
DITHER CYCLE
RATE
DITHER AMOUNT
(±0.5%, ±1.0%, ±1.5%, OR ±2.0%)
CLKIN RANGE (MHz) DITHER RATE
20 TO 134 fIN/832
IF SSEN = 1
Figure 1. DS1181L 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 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.
fSSO
DITHERED
SSEN
DS1181L
Typical Operating Circuit
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 TSSOP H8+3 21-0175
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
DS1181L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
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.
6
_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2007 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 11/07 Initial release. —
1 8/08 Increased the absolute maximum ratings range from +3.63V to +4.3V. 2
