max5528 Maxim Integrated Products, Inc., max5528 Datasheet - Page 10

• Manufacturer Part Number: max5528
• Description: 64-tap, One-time Programmable, Linear-taper Digital Potentiometers
• Manufacturer: Maxim Integrated Products, Inc.

Use the MAX5527/MAX5528/MAX5529 in applications
requiring digitally controlled adjustable resistance,
such as LCD contrast control where voltage biasing
adjusts the display contrast, or for programmable filters
with adjustable gain and/or cutoff frequency.
Figures 7 and 8 show an application where the voltage-
divider or variable resistor is used to make an adjustable,
positive LCD bias voltage. The op-amp provides buffer-
ing and gain to the resistor-divider network made by the
potentiometer (Figure 7), or to a fixed resistor and a
variable resistor (Figure 8).
One-Time Programmable, Linear-Taper Digital
Potentiometers
Figure 7. Positive LCD Bias Control Using a Voltage-Divider
Figure 9. Programmable Filter
10
______________________________________________________________________________________
MAX5527
MAX5528
MAX5529
V
IN
H
MAX5527
MAX5528
MAX5529
Applications Information
R3
W
5V
Positive LCD Bias Control
H
L
L
W
R2
C
H
L
W
5V
R1
30V
V
OUT
V
OUT
Figure 9 shows the configuration for a 1st-order pro-
grammable filter. The gain of the filter is adjusted by
R2, and the cutoff frequency is adjusted by R3. Use the
following equations to calculate the gain (G), and the
-3dB cutoff frequency (f
decade below the wiper -3dB bandwidth.
Figure 10 shows the MAX5527/MAX5528/MAX5529
used as the feedback resistors in an adjustable-voltage
reference application.
Figure 8. Positive LCD Bias Control Using a Variable Resistor
Figure 10. Adjustable Voltage Reference
MAX5527
MAX5528
MAX5529
V
V
V
0
0
0
= 1.23V
= 1.23V
= 1.23V
MAX6160
Adjustable Voltage Reference
GND
+5V
V
100kΩ
R
R
R
10kΩ
IN
50kΩ
f
2
2
2
C
(kΩ)
(kΩ)
(kΩ)
H
L
5V
=
G
OUT
ADJ
FOR THE MAX5528
FOR THE MAX5529
FOR THE MAX5527
2
= +
C
π
), only up to frequencies one
1
W
W
x R x C
R
R
2
1
Programmable Filter
1
R
R
3
H
L
1
2
V
0
REF
30V
MAX5527
MAX5528
MAX5529
V
OUT