AD5255BRU250-RL7 Analog Devices Inc, AD5255BRU250-RL7 Datasheet - Page 18

• Manufacturer Part Number: AD5255BRU250-RL7
• Manufacturer: Analog Devices Inc

Specifications of AD5255BRU250-RL7

• Number Of Elements: 3
• Resistance (max): 250KOhm
• Power Supply Requirement: Single/Dual
• Interface Type: Serial (2-Wire/I2C)
• Single Supply Voltage (typ): 5V
• Dual Supply Voltage (typ): ±2.5V
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (min): ±2.2V
• Dual Supply Voltage (max): ±2.7V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 24
• Lead Free Status / RoHS Status: Not Compliant

AD5255
For RDAC0 and RDAC1:
For RDAC2:
where D is the decimal equivalent of the data contained in the
RDAC register, and R
The output resistance values in Table 11 are set for the given
RDAC latch codes with V
digital potentiometers.
Table 11. R
D (Dec)
511
256
1
0
Note that in the zero-scale condition, a finite wiper resistance of
100 Ω is present. To avoid degradation or possible destruction
of the internal switches, care should be taken to limit the current
flow between W and B to no more than 20 mA intermittently
or 2 mA continuously.
Channel-to-channel R
change in R
coefficient.
Like the mechanical potentiometer that the RDAC replaces, the
AD5255 parts are totally symmetrical. The resistance between
the W wiper and the A terminal also produces a digitally
controlled complementary resistance, R
the B terminal can be floating or tied to the wiper. Setting the
resistance value for R
and decreases as the data loaded in the latch is increased in
value. The general transfer equations for this operation are as
follows.
For RDAC0 and RDAC1:
For RDAC2:
R
R
R
R
WB
WB
WB
WB
( )
( )
( )
( )
D
D
D
D
R
25051
12600
148.8
100
WB
WB
WB
=
=
=
=
at Selected Codes for R
with temperature has a 35 ppm/°C temperature
(D) (Ω)
128
128
512
512
D
D
128
512
×
−
×
−
WA
W
R
D
R
D
WB
AB
AB
is the wiper resistance.
starts at a maximum value of resistance
×
×
matching is better than 0.1%. The
Full scale
Midscale
DD
Output State
1 LSB
Zero scale (wiper contact resistance)
R
R
+
+
AB
AB
= 5 V, which applies to R
R
R
W
W
+
+
R
R
W
W
WB_FS
WA
. When R
= 25 kΩ
WA
AB
is used,
= 25 kΩ
(1)
(2)
(3)
(4)
Rev. A | Page 18 of 20
For example, the following RDAC latch codes set the
corresponding output resistance values, which apply
to R
Table 12. R
D (DEC)
511
256
1
0
The typical distribution of R
±0.1% within the same package. Device-to-device matching
is process lot-dependent, with a worst-case variation of ±15%.
R
PROGRAMMING THE POTENTIOMETER DIVIDER
Voltage Output Operation
The digital potentiometer can be configured to generate an
output voltage at the wiper terminal that is proportional to the
input voltages applied to the A and B terminals. Connecting the
A terminal to 5 V and the B terminal to ground produces an
output voltage at the wiper that can vary between 0 V to 5 V.
Each LSB of voltage is equal to the voltage applied across the
A and B terminals divided by the 2
potentiometer divider.
Since the AD5255 can operate from dual supplies, the general
equations defining the output voltage at V
ground for any given input voltages applied to the A and B
terminals are as follows.
For RDAC0 and RDAC1:
For RDAC2:
Equation 5 assumes that V
wiper resistance is nulled. Operation of the digital potentiometer
in the divider mode results in more accurate operation over
temperature. In this mode, the output voltage is dependent
on the ratio of the internal resistors, not on the absolute value;
therefore, the drift improves to 15 ppm/°C. There is no voltage
polarity restriction between the A, B, and W terminals as long
as the terminal voltage (V
AB
temperature coefficient is 35 ppm/°C.
AB
V
V
W
= 25 kΩ digital potentiometers.
W
( )
( )
D
D
WA
=
=
(D) at Selected Codes for R
512
128
D
D
R
148.8
12600
25051
25100
WA
×
×
(D) (Ω)
V
V
AB
AB
+
+
TERM
W
V
V
AB
is buffered; therefore, the effect of
B
B
) stays within V
from channel-to-channel is
N
Output State
Full scale
Midscale
1 LSB
Zero scale
position resolution of the
AB
W
= 25 kΩ
with respect to
SS
< V
TERM
< V
DD
(5)
(6)
.