ad5171 Analog Devices, Inc., ad5171 Datasheet - Page 15

• Manufacturer Part Number: ad5171
• Description: 64-position Otp Digital Potentiometer
• Manufacturer: Analog Devices, Inc.

VARIABLE RESISTANCE AND VOLTAGE FOR
POTENTIOMETER MODE
If all three terminals are used, the operation is called the
potentiometer mode. The most common configuration is the
voltage divider operation (Figure 32).
Ignoring the effect of the wiper resistance, the
is simply
A more accurate calculation, which includes the wiper
resistance effect, yields
V
V
W
W
(
(
D
D
)
)
=
=
Figure 32. Potentiometer Mode Configuration
63
63
D
D
R
AB
V
R
A
AB
+
V
2
+
I
R
R
W
W
V
A
B
A
W
V
O
transfer function
Rev. B | Page 15 of 24
(3)
(4)
Unlike in rheostat mode where the absolute tolerance is high,
potentiometer mode yields an almost ratio-metric function of
D/63 with a relatively small error contributed by the R
thus, the tolerance effect is almost cancelled. Although the thin
film step resistor (R
very different temperature coefficients, the ratiometric
adjustment also reduces the overall temperature coefficient
effect to 5 ppm/°C, except at low value codes where R
dominates.
Potentiometer mode includes other operations such as op amp
input, feedback resistor networks, and voltage scaling applica-
tions. Terminal A, Terminal W, and Terminal B can, in fact, be
input or output terminals provided that |V
do not exceed V
DD
to GND.
S
) and CMOS switches resistance (R
AB
|, |V
WA
|, and |V
AD5171
W
W
terms;
W
) have
WB
|