AD5254BRUZ100 Analog Devices Inc, AD5254BRUZ100 Datasheet - Page 25

• Manufacturer Part Number: AD5254BRUZ100
• Description: IC POT DGTL QUAD 100K 20-TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5254BRUZ100

• Memory Type: Non-Volatile
• Temperature Coefficient: 650 ppm/°C Typical
• Taps: 256
• Resistance (ohms): 100K
• Number Of Circuits: 4
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 2.7 V ~ 5.5 V, ±2.25 V ~ 2.75 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP
• Resistance In Ohms: 100K
• End To End Resistance: 100kohm
• Track Taper: Linear
• Resistance Tolerance: ± 30%
• No. Of Steps: 256
• No. Of Pots: Quad
• Potentiometer Ic Case: RoHS Compliant
• Supply Voltage Range: ± 2.25V To ± 2.75V
• Control Interface: I2C, Serial
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD5254EVAL - BOARD EVAL FOR AD5254
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Since the digital potentiometer is not ideal, a 75 Ω finite wiper
resistance is present that can easily be seen when the device is
programmed at zero scale. Because of the fine geometric and
interconnects employed by the device, care should be taken to
limit the current conduction between W and B to no more than
±5 mA continuous for a total resistance of 1 kΩ or a pulse of
±20 mA to avoid degradation or possible destruction of the
device. The maximum dc current for AD5253 and AD5254 are
shown in Figure 21 and Figure 22, respectively.
Similar to the mechanical potentiometer, the resistance of the
RDAC between Wiper W and Terminal A also produces a
digitally controlled complementary resistance, R
terminals are used, the B terminal can be opened. The R
starts at a maximum value and decreases as the data loaded into
the latch increases in value (see Figure 43. The general equation
for this operation is
The typical distribution of R
matches is about ±0.15% within a given device. On the other
hand, device-to-device matching is process-lot dependent with
a ±20% tolerance.
100
AD5253: RWA(D) = [(64 – D)/64] × RAB + 75 Ω
AD5254: RWA(D) = [(256 – D)/256] × RAB + 75 Ω
75
50
25
0
0
Figure 43. AD5253 R
R
10
WA
D (Code in Decimal)
WA
(D) and R
AB
32
from channel-to-channel
WB
(D) vs. Decimal Code
R
48
WB
WA
. When these
63
WA
Rev. B | Page 25 of 32
(3)
(4)
PROGRAMMABLE POTENTIOMETER OPERATION
If all three terminals are used, the operation is called potenti-
ometer mode (see Figure 44); the most common configuration
is the voltage divider operation.
If the wiper resistance is ignored, the transfer function is simply
A more accurate calculation that includes the wiper resistance
effect is
where 2
Unlike in rheostat mode operation, where the tolerance is high,
potentiometer mode operation yields an almost ratiometric
function of D/2
R
Similarly, the ratiometric adjustment also reduces the
temperature coefficient effect to 50 ppm/°C, except at low value
codes where R
Potentiometer mode operations include other applications such
as op amp input, feedback-resistor networks, and other voltage-
scaling applications. The A, W, and B terminals can, in fact, be
input or output terminals, provided that |V
not exceed V
W
terms. Therefore, the tolerance effect is almost cancelled.
AD5253:
AD5254:
V
W
N
(
is the number of steps.
D
)
=
Figure 44. Potentiometer Mode Configuration
DD
W
V
V
2
N
to V
V
D
W
W
R
dominates.
N
I
with a relatively small error contributed by the
AB
=
=
R
SS
AB
+
64
256
D
.
D
2
+
×
R
×
R
V
W
V
A
B
W
AB
AB
V
+
+
A
V
V
B
W
B
AD5253/AD5254
V
C
A
|, |V
W
|, and |V
B
| do
(5)
(6)
(7)