CAT5120_07 Datasheet, PDF (5/13 Pages) Catalyst Semiconductor – 16-Tap MiniPot TM Digitally Programmable Potentiometers with 2-Wire Interface

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.
CAT5120, CAT5121, CAT5122
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.
Figure 3. Positive LCD Bias Control
+5V
H
W
CAT5120 L
30V
V_OUT
Figure 4. Positive LCD Bias Control
+5V
H
30V
CAT5121 L
V_OUT
Figure 5a. Adjustable Gain Circuit
V_CC
V_IN
V_OUT
H
CAT5121 L
Figure 5b. Adjustable Gain Circuit
V_CC
V_IN
V_OUT
W
L
H
CAT5120
© 2007 by Catalyst Semiconductor, Inc.

Characteristics subject to change without notice
Doc No. 2121, Rev. C