AD5260BRU200-REEL7 Analog Devices Inc, AD5260BRU200-REEL7 Datasheet - Page 15

• Manufacturer Part Number: AD5260BRU200-REEL7
• Description: IC DGTL POT SNGL 256POS 14-TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5260BRU200-REEL7

• Rohs Status: RoHS non-compliant
• Taps: 256
• Resistance (ohms): 200K
• Number Of Circuits: 1
• 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: 14-TSSOP
• Resistance In Ohms: 200K
• Other names: AD5260BRU200REEL7

8-Bit Bipolar DAC
Figure 16 shows a low cost 8-bit bipolar DAC. It offers the same
number of adjustable steps but not the precision of conventional
DACs. The linearity and temperature coefficients, especially at low
values codes, are skewed by the effects of the digital potentiometer
wiper resistance. The output of this circuit is:
Bipolar Programmable Gain Amplifier
For applications that require bipolar gain, Figure 17 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
REV. 0
V
V
V
O
O
i
Figure 17. Bipolar Programmable Gain Amplifier
GND
V
V
=
V
i
=
IN
Figure 15. Programmable Voltage Reference
i
Ê
Á
Ë
Ê
Á
Ë
V
TRIM
256
1
2
U1
OUT
ADR425
i
D
AD5262
+
and –KV
AD5262
R
R
U2
U1
-
1
2
A2
A1
GND
2
1
V
5V
+5V
1
IN
Figure 16. 8-Bit Bipolar DAC
ˆ
˜ ¥
¯
ˆ
˜ ¥
¯
AD5260
AD1582
REF
V
U1
OUT
W2
W1
i
V
Ê
Á
Ë
at a given U2 setting. Configuring A2 in
A1
B2
B1
OP2177
REF
256
R
D
V
3
B
W
W1
WB1
AD5260
DD
U2
2
V
SS
¥
/R
A
B
A
(
A1
OP2177
1
WA1
R
W
+5V
+
–KV
AD8601
A1
–5V
K
set by U1.
5V
i
)
A2
OP2177
-
V
K
SS
V
5V
ˆ
˜
¯
A2
DD
OP2177
REF
C1
+5V
–5V
V
O
R2
R1
V
V
O
O
(4)
(5)
–15–
Similar to the previous example, in the simpler (and much more
usual) case, where K = 1, a single digital pot AD5260, and U1
is replaced by a matched pair of resistors to apply V
the ends of the digital pot. The relationship becomes:
If R2 is large, a few picofarad compensation capacitors may be
needed to avoid any gain peaking.
Table VIII 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.
Programmable Voltage Source with Boosted Output
For applications that require high current adjustment such as a
laser diode driver or turnable laser, a boosted voltage source can
be considered (see Figure 18).
In this circuit, the inverting input of the op amp forces the V
equal to the wiper voltage set by the digital potentiometer. The
load current is then delivered by the supply via the P-Ch FET P1.
The N-Ch FET N
A1 needs to be the rail-to-rail input type. Resistor R1 is needed to
prevent P1 from not 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; on the other
hand, P1 is driven in the saturation state, and therefore its power
handling must be adequate to dissipate (V
circuit can source a maximum of 100 mA at 5 V supply. Higher
current can be achieved with P1 in a larger package. Note, a single
N-Ch FET can replace P1, N1, and R1 altogether. However, the out-
put swing will be limited unless separate power supplies are used.
For precision application, a voltage reference such as ADR423,
ADR292, and AD1584 can be applied at the input of the digital
potentiometer.
Programmable 4-to-20 mA Current Source
A programmable 4-to-20 mA current source can be implemented
with the circuit shown in Figure 19. REF191 is a unique low
supply headroom and high current handling precision reference
5V
V
V
U1
O
i
Figure 18. Programmable Boosted Voltage Source
=
D
0
64
128
192
255
A
B
Ê
Á
Ë
Table VIII. Result of Bipolar Gain Amplifier
1
W
+
R
R
R1 = •, R2 = 0
–1
–0.5
0
0.5
0.968
2
1
ˆ
˜
¯
A1
Ê
Á
Ë
1
2 2
256
simplifies the op amp driving requirement.
D
R1
-
10k
1
ˆ
˜ ¥
¯
V
i
R1 = R2
–2
–1
0
1
1.937
P1
AD5260/AD5262
N1
i
SIGNAL LO
– V
U1= AD5260
A1= AD8601, AD8605, AD8541
P1= FDP360P, NDS9430
N1= FDV301N, 2N7002
O
)
C
R2 = 9R1
–10
–5
0
5
9.680
C
I
L
power. This
i
R
and – V
BIAS
V
O
O
to be
I
i
(6)
L
at