ad5231 Analog Devices, Inc., ad5231 Datasheet - Page 24

• Manufacturer Part Number: ad5231
• Description: Nonvolatile Memory, 1024-position Digital Potentiometer
• Manufacturer: Analog Devices, Inc.

AD5231
10-BIT UNIPOLAR DAC
Figure 50 shows a unipolar 10-bit DAC using AD5231. The
buffer is needed to drive various leads.
PROGRAMMABLE VOLTAGE SOURCE WITH
BOOSTED OUTPUT
For applications that require high current adjustment, such as a
laser diode driver or tunable laser, a boosted voltage source can
be considered (see Figure 51).
In this circuit, the inverting input of the op amp forces the V
to be equal to the wiper voltage set by the digital potentiometer.
The load current is then delivered by the supply via the
N-Ch FET N
(V
100 mA with a 5 V supply.
For precision applications, a voltage reference such as ADR421,
ADR03, or
potentiometer.
+5V
V
GND
i
IN
− V
ADR421
V
TRIM
V
OUT
IN
O
) × I
+2.5VREF
A
ADR370
1
2
B
Figure 51. Programmable Booster Voltage Source
5V
V
GND
AD5231
L
IN
1
AD5231
W
. N
power. This circuit can source a maximum of
U1
V
AD1582
U1
OUT
1
power handling must be adequate to dissipate
AD8601
U2
R
Figure 50. 10-Bit Unipolar DAC
Figure 49. 10-Bit Bipolar DAC
3
can be applied at Terminal A of the digital
AD5231
W
B
V+
V–
A
B
A
A1
AD8552
W
2N7002
V+
V–
R
+5V
–5V
A1
AD8601
V+
V–
5V
–2.5VREF
SIGNAL C
AD8552
LD
A2
C
V+
V–
V
–5V
+5V
O
R
BIAS
V
I
OUT
L
V
O
Rev. C | Page 24 of 28
OUT
PROGRAMMABLE CURRENT SOURCE
A programmable current source can be implemented with the
circuit shown in Figure 52.
REF191
that can deliver the 20 mA needed at 2.048 V. The load current
is simply the voltage across Terminals B–W of the digital
potentiometer divided by R
The circuit is simple, but be aware that there are two issues.
First, dual-supply op amps are ideal because the ground
potential of REF191 can swing from −2.048 V at zero scale to V
at full scale of the potentiometer setting. Although the circuit
works under single-supply, the programmable resolution of the
system is reduced. Second, the voltage compliance at V
limited to 2.5 V or equivalently a 125 Ω load. Should higher
voltage compliance be needed, users can consider digital
potentiometers AD5260, AD5280, and AD7376. Figure 53
shows an alternate circuit for high voltage compliance.
To achieve higher current, such as when driving a high power
LED, the user can replace the UI with an LDO, reduce R
add a resistor in series with the digital potentiometer’s
A terminal. This limits the potentiometer’s current and
increases the current adjustment resolution.
I
L
=
is a unique low supply, headroom precision reference
3
R
V
SLEEP
GND
+5V
V
2
4
S
IN
–2.048V TO V
REF
REF191
×
Figure 52. Programmable Current Source
1024
×
U1
AD5231
D
V
OUT
L
6
0V TO (2.048V + V
S
C1
1µF
:
V+
V–
OP1177
+5V
–5V
U2
B
A
–
+
W
L
100Ω
)
R
L
R
102Ω
S
V
L
I
L
L
is
S
, and
(7)
L