CAT5121_13 Datasheet, PDF (6/11 Pages) ON Semiconductor – 16‐tap Digital Potentiometers (POTs)

CAT5120, CAT5121, CAT5122
APPLICATIONS INFORMATION
The devices 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 9) to
select a portion of the input signal by digitally controlling the
wiper terminal. Figure 10 shows a similar circuit for the
CAT5121.
Adjustable Gain
Figures 11 and 12 show 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 devices have a low 5 ppm/C
ratiometric tempco that allows for a very stable adjustable
gain configuration over temperature.
+5 V
H
W
CAT5120 ^L
30 V
V_OUT
+5 V
H
CAT5121 ^L
30 V
V_OUT
Figure 9. Positive LCD Bias Control
V_CC
V_IN
V_OUT
H
CAT5121 L
Figure 11. Adjustable Gain Circuit
Figure 10. Positive LCD Bias Control
V_CC
V_IN
V_OUT
LW
H
CAT5120
Figure 12. Adjustable Gain Circuit
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