AD5262BRUZ20 Analog Devices Inc, AD5262BRUZ20 Datasheet - Page 20

• Manufacturer Part Number: AD5262BRUZ20
• Description: IC POT DUAL 20K 256POS 16TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5262BRUZ20

• Taps: 256
• Resistance (ohms): 20K
• Number Of Circuits: 2
• Temperature Coefficient: 35 ppm/°C Typical
• Memory Type: Volatile
• Interface: 4-Wire SPI Serial
• Voltage - Supply: 4.5 V ~ 16.5 V, ±4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP
• Resistance In Ohms: 20K
• End To End Resistance: 20kohm
• Track Taper: Linear
• No. Of Steps: 256
• Resistance Tolerance: ± 30%
• Supply Voltage Range: 4.5V To 16.5V, ± 4.5V To ± 5.5V
• Control Interface: Serial, SPI
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5260/AD5262
BIPOLAR PROGRAMMABLE GAIN AMPLIFIER
For applications that require bipolar gain, Figure 62 shows one
implementation. Digital Potentiometer U1 sets the adjustment
range. The wiper voltage at W2 can therefore be programmed
between V
the noninverting mode allows linear gain and attenuation. The
transfer function is
where K is the ratio of R
Similar to the previous example, in the simpler and more
common case, where K = 1, with a single digital potentiometer,
AD5260, U1 is replaced by a matched pair of resistors to apply
V
ship becomes
If R2 is large, a few picofarad compensation capacitors may be
needed to avoid any gain peaking.
Table 11 shows the result of adjusting D, with A2 configured as
a unity gain, a gain of 2, and a gain of 10. The result is a bipolar
amplifier with linearly programmable gain and 256-step
resolution.
Table 11. Result of Bipolar Gain Amplifier
D
0
64
128
192
255
i
and −V
V
i
V
V
V
O
AD5262
O
i
=
=
U2
AD5262
R1 = ∞, R2 = 0
−1
−0.5
0
+0.5
+0.968
i
i
at the ends of the digital potentiometer. The relation-
⎛ +
⎜
⎝
⎛ +
⎜
⎝
and −KV
Figure 62. Bipolar Programmable Gain Amplifier
1
1
U1
A2
A1
R2
R1
R2
R1
⎞
⎟
⎠
W2
W1
⎞
× ⎟
⎠
⎛
⎜
⎝
B2
B1
A1
i
OP2177
2
256
at a given U2 setting. Configuring A2 in
⎛
⎜
⎝
D
V
256
DD
D
2
WB1
V
2
SS
−
/R
×
1
⎞
× ⎟
⎠
(
WA1
1
+
V
–KV
set by U1.
K
i
R1 = R2
−2
−1
0
+1
+1.937
)
i
A2
−
OP2177
V
K
V
DD
SS
⎞
⎟
⎠
C1
R2 = 9 × R1
−10
−5
0
+5
+9.680
R2
R1
V
O
Rev. A | Page 20 of 24
(5)
(6)
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 63).
In this circuit, the inverting input of the op amp forces V
equal to the wiper voltage set by the digital potentiometer. The
load current is then delivered by the supply via the P-channel
FET, P1. The N-channel FET, N
requirement. A1 must be the rail-to-rail input type. Resistor R1
is needed to prevent P1 from turning off once it is on. The choice
of R1 is a balance between the power loss of this resistor and
the output turn-off time. N1 can be any general-purpose signal
FET. However, P1 is driven in the saturation state, and there-
fore, its power handling must be adequate to dissipate (V
× I
supply. Higher current can be achieved with P1 in a larger pack-
age. Note that a single N-channel FET can replace P1, N1, and
R1 altogether. However, the output swing is limited unless sepa-
rate power supplies are used. For a precision application, a
voltage reference such as the ADR423, ADR292, or
be applied at the input of the digital potentiometer.
PROGRAMMABLE 4 mA-TO-20 mA CURRENT
SOURCE
A programmable 4 mA-to-20 mA current source can be
implemented with the circuit shown in Figure 64.
unique low supply headroom and high current handling
precision reference that can deliver 20 mA at 2.048 V. The load
current is simply the voltage across Terminal B to Terminal W
of the digital potentiometer, divided by R
5V
V
U1
i
L
power. This circuit can source a maximum of 100 mA at 5 V
I
A
B
L
W
=
V
Figure 63. Programmable Boosted Voltage Source
REF
R
A1
S
×
D
R1
10kΩ
1
P1
, simplifies the op amp driving
N1
SIGNAL LO
U1 = AD5260
A1 = AD8601, AD8605, AD8541
P1 = FDP360P, NDS9430
N1 = FDV301N, 2N7002
S
.
C
C
REF191
R
BIAS
AD1584
V
O
O
i
− V
I
to be
is a
L
can
(7)
O
)