AD5260BRU200-REEL7 Analog Devices Inc, AD5260BRU200-REEL7 Datasheet - Page 16

• 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

AD5260/AD5262
that can deliver 20 mA at 2.048 V. The load current is simply the
voltage across terminals B-to-W of the digital pot divided by R
The circuit is simple, but be aware that dual-supply op amps are
ideal because the ground potential of REF191 can swing from
–2.048 V at zero scale to V
setting. Although the circuit works under single supply, the pro-
grammable resolution of the system will be reduced.
Programmable Bidirectional Current Source
For applications that require bidirectional current control or higher
voltage compliance, a Howland current pump can be a solution
(see Figure 20). If the resistors are matched, the load current is:
AD5260
Figure 20. Programmable Bidirectional Current Source
I
I
Figure 19. Programmable 4-to-20 mA Current Source
L
L
=
=
3
V
(
R A
–5V
REF
A
B
2
4
+5V
V
SLEEP
GND
IN
2
5V
R
REF191
–2.048V TO V
W
S
U1
¥
+
R B
D
V
OUT
2
R B R
2
A1
OP2177
6
+15V
–15V
)
L
1 F
/
C1
0 TO (2.048
1
L
¥
at full scale of the potentiometer
V
AD5260
W
150k
150k
10pF
V
R1
C2
R1
L
)
U2
OP1177
+5V
–5V
B W
A
–
+
10pF
AD8016
C1
14.95k
+15V
15k
–15V
R2
R2A
R
102
R
100
S
L
A2
50
V
R
R
500
L
L
L
I
L
V
(7)
(8)
I
L
L
S
.
–16–
Programmable Low-Pass Filter
Digital potentiometer AD5262 can be used to construct a second
order Sallen Key Low-Pass Filter (see Figure 21). The design
equations are:
Users can first select some convenient values for the capacitors.
To achieve maximally flat bandwidth where Q = 0.707, let C1 be
twice the size of C2 and let R1 = R2. As a result, users can adjust
R1 and R2 to the same settings to achieve the desirable bandwidth.
Programmable Oscillator
In a classic Wien-bridge oscillator, Figure 22, the Wien network
(R, R’, C, C’) provides positive feedback, while R1 and R2
provide negative feedback. At the resonant frequency, f
overall phase shift is zero, and the positive feedback causes the
circuit to oscillate. With R = R’, C = C’, and R2 = R2A//(R2B+
R
where R is equal to R
At resonance, setting
balances the bridge. In practice, R2/R1 should be set slightly larger
than 2 to ensure the oscillation can start. On the other hand, the
alternate turn-on of the diodes D1 and D2 ensures R2/R1 to be
smaller than 2 momentarily and therefore stabilizes the oscillation.
Once the frequency is set, the oscillation amplitude can be tuned
by R2B since:
DIODE
V
w
Q
w
R
V
2
3
R
R
O
O
O
V
i
2
1
=
=
O
=
=
=
V
), the oscillation frequency is:
=
R C
256
i
=
S
RC
2
1 1
1
256
Figure 21. Sallen Key Low-Pass Filter
1
I R B V
R R C C
2
D
1 2 1 2
–
+
+
D
A
ADJUSTED TO
SAME SETTINGS
w
R
2
Q
R1
w
1
O
R C
or
R
W
O
2 2
B
S
+
1
AB
2
f
O
+
WA
D
w
=
A
R
O
R2
2
such that:
2
p
W
C2
B
1
RC
C1
AD8601
+2.5V
–2.5V
V
o
O
, the
REV. 0
(10)
(11)
(12)
(13)
(14)
(15)
(9)