CAT5110 Datasheet, PDF (8/11 Pages) Catalyst Semiconductor – 32-Tap MiniPot Digitally Programmable Potentiometers with 2-Wire Interface

CAT5110/5118/5119
APPLICATIONS INFORMATION
The Minipots are intended for circuits requiring digitally
controlled adjustable resistance, such as LCD contrast
control, where voltage biasing adjusts the display con-
trast.
Alternative Positive LCD Bias Control
Use an op amp to provide buffering and gain on the
output of the CAT5110. 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 CAT5119.
Adjustable Gain
Figure 5 shows how to use the variable resistor to
digitally adjust the gain of a noninverting op amp
configuration. Connect the CAT5119 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.
Figure 3. Positive LCD Bias Control
+5V
H
W
CAT5110 L
30V
V_OUT
Figure 4. Positive LCD Bias Control
+5V
H
CAT5119 L
30V
V_OUT
Figure 5a. Adjustable Gain Circuit
V_CC
V_IN
V_OUT
H
L CAT5119
Figure 5b. Adjustable Gain Circuit
V_CC
V_IN
V_OUT
W
L
H
CAT5110
Doc. No. 2120, Rev. A
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