CAT5120_08 Datasheet, PDF (5/12 Pages) Catalyst Semiconductor – 16-Tap MiniPot™ Digitally Programmable Potentiometers with 2-Wire Interface

CAT5120, CAT5121, CAT5122
APPLICATIONS INFORMATION
The MiniPots are intended for circuits requiring
digitally controlled adjustable resistance, such as LCD
contrast control, where voltage biasing adjusts the
display contrast.
Alternative Positive LCD Bias Control
Use an op amp to provide buffering and gain on the
output of the CAT5120. Connect the mechanical
potentiometer to the positive input of a noninverting op
amp (Figure 3) to select a portion of the input signal
by digitally controlling the wiper terminal. Figure 4
shows a similar circuit for the CAT5121.
Adjustable Gain
Figure 5 shows how to use the variable resistor to
digitally adjust the gain of a noninverting op amp
configuration. Connect the CAT5121 in series with a
resistor to ground to form the adjustable gain control
of a noninverting amplifier. The Minipots have a low
5ppm/°C ratiometric tempco that allows for a very
stable adjustable gain configuration over temperature.
+5V
H
W
CAT5120 L
30V
V_OUT
+5V
H
CAT5121 L
30V
V_OUT
Figure 3. Positive LCD Bias Control
Figure 4. Positive LCD Bias Control
V_CC
V_IN
V_OUT
V_CC
V_IN
V_OUT
H
CAT5121 L
W
L
H
CAT5120
Figure 5a. Adjustable Gain Circuit
© Catalyst Semiconductor, Inc.
5
Characteristics subject to change without notice
Figure 5b. Adjustable Gain Circuit
Doc. No. MD-2121 Rev. E