Detailed Description
The DS1083L modulates an input clock to provide a cen-
ter-dithered spread-spectrum output. A 16MHz to
134MHz clock is applied to the CLKIN pin. The PLL
dithers the output clock about its center frequency at a
user-selectable magnitude. The user is required to cycle
power to the device each time there is a change in the
input frequency, for the PLL to lock correctly. This
ensures proper output frequency and dither rate. The
desired spread-spectrum magnitude is selected using
input pins SMSEL1 and SMSEL2 (see the
Pin Description
for details). The DS1083L is capable of generating
spread-spectrum clocks from 16MHz to 134MHz.
Dither-Rate Selection
The output spread-spectrum dither rate is automatically
adjusted depending on the input frequency, to maxi-
mize EMI reduction.
The dither cycle rate is:
f
IN
/512, if f
IN
is between 16MHz and 33MHz
f
IN
/1024, if f
IN
is between 33MHz and 64MHz
f
IN
/2048, if f
IN
is between 64MHz and 134MHz
On power-up, the output clock (SSO) remains three-
stated until it reaches a stable frequency (f
SSO
). The
dither rate is selected by sampling the input clock at
power-up.
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.
Chip Information
SUBSTRATE CONNECTED TO GROUND
DS1083L
16MHz to 134MHz Spread-Spectrum
Clock Modulator for LCD Panels
4 _______________________________________________________________________________________
Pin Description
PIN NAME DESCRIPTION
1
CLKIN
Clock Input. 16MHz to 134MHz clock input (f
IN
).
2
GND Ground
3
SSO
Spread-Spectrum Clock Output. Outputs a center-dithered spread-spectrum version of the clock input at
CLKIN.
Spread-Spectrum Magnitude Select Inputs. These digital inputs select the desired spread-spectrum
magnitude as shown in the table below. Both inputs contain pullup resistors (R
PU
) to V
CC
.
SMSEL2 SMSEL1 MAGNITUDE SELECTED (%)
4 SMSEL2
0 0 ±2
0 1 ±1.5
1 0
±1
5SMSEL1
1 1 ±0.5
6 VCC Supply Voltage
