AD5232

Manufacturer Part NumberAD5232
Description2-Channel/ 256-Position Digital Potentiometer
ManufacturerAnalog Devices
AD5232 datasheet
 


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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
N
2
position resolution of the potentiometer divider. The general
equation defining the output voltage with respect to ground for
any given input voltage applied to terminals AB is:
N
V
(Dx) = Dx/2
V
W
AB
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
as the terminal voltage (V
) stays within V
TERM
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.
V
CS
V
SS
DD
DD
CLK
SCLK
C
MOSI
SDI
GND
GND
V
AD5232
SS
RDAC
10k
A
C
A
C
W
60pF
C
= 45pF
A
W
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 resistor) measures 500 kHz at half scale. Figure TPC 10
provides the large signal BODE plot characteristics of the three
resistor versions 10 k , 50 k , and 100 k . 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 RDAC:
Listing I. Macro Model Net List for RDAC
.PARAM DW=255, RDAC=10E3
*
+ V
(3)
B
.SUBCKT DPOT (A,W,B)
*
CA
A
RAW
A
< V
< V
.
CW
W
SS
TERM
DD
RBW
W
CB
B
*
.ENDS DPOT
+2.75V
APPLICATION PROGRAMMING EXAMPLES
The following command sequence examples have been developed
to illustrate a typical sequence of events for the various features
2V p-p
of the AD5232 nonvolatile digital potentiometer.
~
1V p-p
[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
–2.5V
SDI
B140
H
B
B080
H
C
B
C
= 45pF
B
AD5232
0
{45E-12}
W
{(1-DW/256)*RDAC+50}
0
60E-12
B
{DW/256*RDAC+50}
0
{45E-12}
SDO
Action
XXXX
Loads 40
data into RDAC2 register,
H
H
Wiper W2 moves to 1/4 full-scale
position.
B140
Loads 80
data into RDAC1 register,
H
H
Wiper W1 moves to 1/2 Full-Scale
position.