Datasheet
DS1081L
20MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
4 _______________________________________________________________________________________
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.
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
(f
IN
) so that the appropriate dither rate is programmed.
Pin Description
PIN NAME FUNCTION
1
CLKIN
Clock Input. 20MHz to 134MHz clock input (f
IN
).
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%
4
GND Ground
5 SSEN
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.
CRSEL CLKIN RANGE DITHER RATE
0 66MHz to 134MHz f
IN
/2048
Open 33MHz to 80MHz f
IN
/1024
7 CRSEL
1 20MHz to 38MHz f
IN
/512
8
V
CC
Supply Voltage
CRSEL CLKIN RANGE DITHER RATE
0 66MHz to 134MHz f
IN
/2048
Open 33MHz to 80MHz f
IN
/1024
1 20MHz to 38MHz f
IN
/512
Table 2. Spread-Spectrum Dither Rate
SMSEL2
SMSEL1 MAGNITUDE
00±2.0%
01±1.5%
10±1.0%
11±0.5%
Table 1. Spread-Spectrum Dither Magnitude