AD5232 Analog Devices, AD5232 Datasheet - Page 13

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AD5232

Manufacturer Part Number
AD5232
Description
2-Channel/ 256-Position Digital Potentiometer
Manufacturer
Analog Devices
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
2
equation defining the output voltage with respect to ground for
any given input voltage applied to terminals AB is:
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
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.
N
position resolution of the potentiometer divider. The general
C
GND
V
DD
SCLK
MOSI
SS
C
A
V
= 45pF
W
A
(Dx) = Dx/2
C
A
CS
CLK
SDI
GND
AD5232
TERM
RDAC
10k
) stays within V
W
N
60pF
C
W
V
AB
V
V
SS
DD
+ V
C
C
B
B
B
= 45pF
B
SS
1V p-p
< V
2V p-p
TERM
~
+2.75V
< V
–2.5V
DD
(3)
.
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
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.
SDI
B140
B080
.PARAM DW=255, RDAC=10E3
*
.SUBCKT DPOT (A,W,B)
*
CA
RAW
CW
RBW
CB
*
.ENDS DPOT
Table IX. Set Two Digital POTs to Independent Data Values
H
H
A
A
W
W
B
SDO
XXXX
B140
0
W
0
B
0
H
{45E-12}
{(1-DW/256)*RDAC+50}
60E-12
{DW/256*RDAC+50}
{45E-12}
H
Action
Loads 40
Wiper W2 moves to 1/4 full-scale
position.
Loads 80
Wiper W1 moves to 1/2 Full-Scale
position.
H
H
data into RDAC1 register,
data into RDAC2 register,
AD5232

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