AS1506_1 datasheet(13/17 Pages) AMSCO

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AS1506

Datasheet - 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 AS1506 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 24 shows the configuration for a 1st-order programmable filter.

The DC gain of the filter is adjusted by R2 and can be calculated as:

G = 1 + (R1/R2)(EQ 1)

The cutoff frequency (fC) is adjusted by R3, and can be calculated as:

fC = 1/(2

π x R3 x C)

(EQ 2)

Figure 24. Programmable Filter Circuit

Offset Voltage and Gain Adjustment

Connect the AS1506 to an op amp to nullify the offset voltage over the operating temperature range. Install another

AS1506 potentiometer in the feedback path to adjust the gain of the op amp (Figure 25).

Figure 25. Offset Voltage Adjustment Circuit

–

VIN

VOUT

CIN

AS1506

HIGH

WIPER

LOW

HIGH

WIPER

LOW

AS1506

–

AS1506

AS1506 Datasheet(PDF) 13 Page - ams AG