AD5110BCPZ10-1-RL7 AD [Analog Devices], AD5110BCPZ10-1-RL7 Datasheet - Page 25

• Manufacturer Part Number: AD5110BCPZ10-1-RL7
• Manufacturer: AD [Analog Devices]

Data Sheet
Similar to the mechanical potentiometer, the resistance of
the RDAC between the W terminal and the A terminal also
produces a digitally controlled complementary resistance, R
R
starts at the maximum resistance value and decreases as the
data loaded into the latch increases. The general equations for
this operation are
AD5110:
AD5112:
AD5114:
where:
D is the decimal equivalent of the binary code in the 5-/6-/7-bit
RDAC register.
R
R
R
In the bottom-scale condition or top-scale condition, a finite
total wiper resistance of 45 Ω is present. Regardless of which
setting the part is operating in, take care to limit the current
between Terminal A to Terminal B, Terminal W to Terminal A,
and Terminal W to Terminal B, to the maximum continuous
current of ±6 mA or to the pulse current specified in Table 6.
Otherwise, degradation or possible destruction of the internal
switch contact can occur.
Calculating the Actual End-to-End Resistance
The resistance tolerance is stored in the internal memory
during factory testing. The actual end-to-end resistance can,
therefore, be calculated, which is valuable for calibration,
tolerance matching, and precision applications.
The resistance tolerance in percentage is stored in fixed-point
format, using an 8-bit sign magnitude binary. The data can be
read back by executing Command 6 and setting Bit DB0 (A0).
The MSB is the sign bit (0 = − and 1 = +) and the next four bits
are the integer part, the fractional part is represented by the
three LSBs, as shown in Table 11.
AB
W
TS
WA
is the wiper resistance.
is the wiper resistance at top scale.
is the end-to-end resistance.
also gives a maximum of 8% absolute resistance error. R
R
R
R
R
R
R
R
R
R
AW
AW
AW
AW
AW
AW
AW
AW
AW
(
(
(
=
=
=
=
=
=
D
D
D
R
R
R
R
R
R
)
)
)
TS
TS
TS
AB
=
AB
=
AB
=
128
64
32
+
+
+
128
64
32
R
R
R
−
−
W
W
W
−
D
D
D
×
×
×
R
R
R
AB
AB
AB
+
+
+
R
R
R
W
W
W
Bottom scale (0xFF) (10)
Bottom scale (0xFF) (13)
Bottom scale (0xFF) (7)
From 0x00 to 0x3F (11)
From 0x00 to 0x1F (14)
From 0x00 to 0x7F (8)
Top scale (0x40) (12)
Top scale (0x20) (15)
Top scale (0x80) (9)
WA
Rev. 0 | Page 25 of 28
WA
.
Table 11. Tolerance Format
DB7
Sign
For example, if R
01010010, the end-to-end resistance can be calculated as,
if,
DB[7] is 0 = negative
DB[6:3] is 1010 = 10
DB[2:0] is 010 = 2 × 2
then,
tolerance = −10.25% and, therefore, R
PROGRAMMING THE POTENTIOMETER DIVIDER
Voltage Output Operation
The digital potentiometer easily generates a voltage divider at
wiper-to-B and wiper-to-A that is proportional to the input
voltage at A to B, as shown in Figure 48. Unlike the polarity of
V
to-A, and W-to-B can be at either polarity.
Connecting Terminal A to 5 V and Terminal B to ground
produces an output voltage at the Wiper W to Terminal B
ranging from 0 V to 5 V. The general equation defining the
output voltage at V
voltage applied to Terminal A and Terminal B, is:
where:
R
R
Operation of the digital potentiometer in the divider mode
results in a more accurate operation over temperature. Unlike
the rheostat mode, the output voltage is dependent mainly on
the ratio of the internal resistors, R
absolute values. Therefore, the temperature drift reduces to
5 ppm/°C.
WB
AW
DD
(D) can be obtained from Equation 1 to Equation 6.
(D) can be obtained from Equation 7 to Equation 15.
to GND, which must be positive, voltage across A-to-B, W-
V
W
DB6
2
(
4
D
)
=
Figure 48. Potentiometer Mode Configuration
R
DB5
2
WB
R
3
AB
AB
(
= 10 kΩ and the data readback shows
W
D
with respect to ground for any valid input
)
V
−3
I
×
DB4
2
= 0.25
2
V
AD5110/AD5112/AD5114
A
Data Byte
+
A
B
R
DB3
2
AW
W
R
1
AB
(
AW
D
)
V
and R
AB
×
.
O
V
= 8.975 kΩ
B
WB
DB2
2
-1
, and not the
DB1
2
-2
DB0
2
(16)
-3