EVAL-AD5111SDZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
EVAL-AD5111SDZ
Analog Devices
'EVAL-AD5111SDZ' PDF : 24 Pages View PDF
AD5111/AD5113/AD5115
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, RWA.
RWA starts at the maximum resistance value and decreases as the
data loaded into the latch increases. The general equations for
this operation are
AD5111:
RAW = RAB + RW
RAW
(D)
=
128 − D
128
×
RAB
+
RW
RAW = RTS
Bottom scale (7)
From 0 to 127 (8)
Top scale (9)
AD5113:
RAW = RAB + RW
RAW (D)
=
64 − D
64
× RAB
+
RW
RAW = RTS
Bottom scale (10)
From 0 to 63 (11)
Top scale (12)
AD5115:
RAW = RAB + RW
Bottom scale (13)
RAW (D)
=
32 − D
32
× RAB
+
RW
From 0 to 31 (14)
RAW = RTS
Top scale (15)
where:
D is the decimal equivalent of the binary code in the 5-/6-/7-bit
RDAC register; 128, 64, and 32 refer to top scale step.
RAB is the end-to-end resistance.
RW is the wiper resistance.
RTS is the wiper resistance at top scale.
Regardless of which setting the part is operating in, take care
to limit the current between A to B, W to A, and W to B, to
the maximum continuous current of ±6 mA (5 kΩ and 10 kΩ)
or ±1.5 mA (80 kΩ), or pulse current specified in Table 6.
Otherwise, degradation or possible destruction of the internal
switch contact can occur.
Data Sheet
PROGRAMMING THE POTENTIOMETER DIVIDER
Voltage Output Operation
The digital potentiometer easily generates a voltage divider at
W-to-B and W-to-A that is proportional to the input voltage at
A-to-B, as shown in Figure 44. Unlike the polarity of VDD to
GND, which must be positive, current across A-to-B, W-to-A,
and W-to-B can be in either direction.
VI
A
W
VO
B
Figure 44. Potentiometer Mode Configuration
If ignoring the effect of the wiper resistance for simplicity,
connecting Terminal A to 5 V and Terminal B to ground
produces an output voltage at W to B ranging from 0 V to 5 V.
The general equation defining the output voltage at VW with
respect to ground for any valid input voltage applied to
Terminal A and Terminal B, is
VW (D)
=
RWB (D)
RAB
×VA
+
RAW (D)
RAB
×VB
(16)
where:
RWB(D) can be obtained from Equation 1 to Equation 6.
RAW(D) can be obtained from Equation 7 to Equation 14.
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, RWA and RWB, and not the
absolute values. Therefore, the temperature drift reduces to
5 ppm/°C.
TERMINAL VOLTAGE OPERATING RANGE
The AD5111/AD5113/AD5115 are designed with internal
ESD diodes for protection. These diodes also set the voltage
boundary of the terminal operating voltages. Positive signals
present on the A, B, or W terminals that exceed VDD are
clamped by the forward-biased diode. There is no polarity
constraint between VA, VW, and VB, but they cannot be higher
than VDD or lower than GND.
Rev. B | Page 20 of 24
Share Link: 