REV. 0

AD5232

–13–

PROGRAMMING THE POTENTIOMETER DIVIDER

Voltage Output Operation

The digital potentiometer easily generates an output voltage

proportional to the input voltage applied to a given terminal.

For example, connecting A-terminal to 5 V and B-terminal to

ground produces an output voltage at the wiper which can be

any value starting at zero volts up to 5 V. Each LSB of voltage is

equal to the voltage applied across terminal AB divided by the

2

equation defining the output voltage with respect to ground for

any given input voltage applied to terminals AB is:

N

× V

(3)

Operation of the digital potentiometer in the divider mode results in

more accurate operation over temperature. Here the output voltage is

dependent on the ratio of the internal resistors, not the absolute

value; therefore, the drift improves to 15 ppm/

°C. There is no

voltage polarity restriction between terminals A, B, and W, as long

OPERATION FROM DUAL SUPPLIES

The AD5232 can be operated from dual supplies enabling con-

trol of ground-referenced ac signals. See Figure 11 for a typical

circuit connection.

~

2V p-p

AD5232

GND

SDI

CLK

SS

SCLK

MOSI

GND

C

1V p-p

+2.75V

–2.5V

CS

Figure 11. Operation from Dual Supplies

AB

RDAC

10k

W

60pF

Figure 12. RDAC Circuit Simulation Model for RDAC = 10 k

Ω

The internal parasitic capacitances and the external capacitive loads

dominate the ac characteristics of the RDACs. Configured as a

potentiometer divider the –3 dB bandwidth of the AD5232BRU10

(10 k

Ω resistor) measures 500 kHz at half scale. Figure TPC 10

provides the large signal BODE plot characteristics of the three

resistor versions 10 k

Ω, 50 kΩ, and 100 kΩ. A parasitic simu-

lation model has been developed, and is shown in Figure 12.

Listing I provides a macro model net list for the 10 k

Ω RDAC:

Listing I. Macro Model Net List for RDAC

.PARAM DW=255, RDAC=10E3

*

.SUBCKT DPOT (A,W,B)

*

CA

A

0

{45E-12}

RAW

A

W

{(1-DW/256)*RDAC+50}

CW

W

0

60E-12

RBW

W

B

{DW/256*RDAC+50}

CB

B

0

{45E-12}

*

.ENDS DPOT

APPLICATION PROGRAMMING EXAMPLES

The following command sequence examples have been developed

to illustrate a typical sequence of events for the various features

of the AD5232 nonvolatile digital potentiometer.

[PCB = Printed Circuit Board containing the AD523x part].

Instruction numbers (Commands), addresses and data appear-

ing at SDI and SDO pins are listed in hexadecimal.

Table IX. Set Two Digital POTs to Independent Data Values

SDI

SDO

Action

Wiper W2 moves to 1/4 full-scale

position.

Wiper W1 moves to 1/2 Full-Scale

position.