AS1507 austriamicrosystems AG, AS1507 Datasheet - Page 13

• Manufacturer Part Number: AS1507
• Description: Dual 256-Tap Digital Potentiometer
• Manufacturer: austriamicrosystems AG

AS1507
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
The AS1507 is intended for circuits requiring digitally controlled adjustable resistance, such as LCD contrast control
(where voltage biasing adjusts the display contrast), or programmable filters with adjustable gain and/or cutoff fre-
quency.
Programmable Filter
Figure 25
The DC gain of the filter is adjusted by R
The cutoff frequency (f
Figure 25. Programmable Filter Circuit
Offset Voltage and Gain Adjustment
Connect one potentiometer of the AS1507 to an op amp to nullify the offset voltage over the operating temperature
range. Use the second potentiometer in the feedback path to adjust the gain of the op amp
Figure 26. Offset Voltage and Gain Adjustment Circuit
www.austriamicrosystems.com
shows the configuration for a 1st-order programmable filter.
C
) is adjusted by R
WIPERA
V
WIPERA
IN
LOWA
HIGHA
LOWA
C
HIGHA
IN
2
3
and can be calculated as:
R
, and can be calculated as:
3
AS1507
5V
f
C
AS1507
+
–
LOWB
HIGHB
G = 1 + (R
= 1/(2
LOWB
HIGHB
Revision 1.00
R
π
2
x R
WIPERB
1
/R
3
+
–
WIPERB
x C)
2
)
R
1
V
OUT
(Figure
www.DataSheet4U.com
26).
13 - 17
(EQ 1)
(EQ 2)