AD5113 AD [Analog Devices], AD5113 Datasheet - Page 14

• Manufacturer Part Number: AD5113
• Manufacturer: AD [Analog Devices]

AD5116
END SCALE RESISTANCE INDICATOR
When the auto save mode is enabled, the ASE pin also indicates
when the RDAC register reaches the maximum or minimum
scale. The
as PD or PU is active, and the part is placed in the end scale
resistance (R
configuration is shown in Figure 40.
When the part is placed at the end of the resistance scale (R
R
the RDAC register is incremented (R
activating PU or PD.
RDAC ARCHITECTURE
To achieve optimum performance, Analog Devices, Inc., has
patented the RDAC segmentation architecture for all the digital
potentiometers. In particular, the
segmentation approach as shown in Figure 41. The
wiper switch is designed with the transmission gate CMOS
topology and with the gate voltage derived from V
Top Scale/Bottom Scale Architecture
In addition, the
resistance between terminals. These extra steps are called
bottom scale and top scale. At bottom scale, the typical wiper
resistance decreases from 70 Ω to 45 Ω. At top scale, the
resistance between Terminal A and Terminal W is decreased
by 1 LSB and the total resistance is reduced to 70 Ω. The extra
steps are not equal to 1 LSB and are not included in the INL,
DNL, R-INL, and R-DNL specifications.
BS
), the ASE pin is pulled high during the debounce time, until
DECODER
ADDRESS
6-BIT
AD5116
TS
Figure 40. Typical End Scale Indicator Circuit
or R
AD5116
100kΩ
Figure 41. Simplified RDAC Circuit
pulls the ASE pin high and holds it as long
BS
), as shown in Figure 6. The typical pin
A
B
includes a new feature to reduce the
ASE
R
R
R
R
L
L
L
L
AD5116
AD5116
BS
TS
BS
) or decremented (R
GND
R
R
employs a two-stage
W
W
S
W
DD
AD5116
.
W
TS
TS
) by
Rev. 0 | Page 14 of 16
or
PROGRAMMING THE VARIABLE RESISTOR
Rheostat Operation—±8% Resistor Tolerance
The
are used as a variable resistor. The unused terminal can be
floating or tied to the W terminal as shown in Figure 42.
The nominal resistance between Terminal A and Terminal B,
R
accessed by the wiper terminal. The 6-bit data in the RDAC
latch is decoded to select one of the 64 possible wiper settings.
The general equation for determining the digitally programmed
output resistance between the W terminal and B terminal is:
where:
D is the decimal equivalent of the binary code in the 6-bit
RDAC register.
R
R
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
data loaded into the latch increases. The general equation for
this operation is:
where:
D is the decimal equivalent of the binary code in the 6-bit
RDAC register.
R
R
R
Regardless of which setting the part is operating in, take care
to limit the current between the A terminal to B terminal, W
terminal to A terminal, and W terminal to B terminal, to the
maximum continuous current or pulsed current specified in
Table 4. Otherwise, degradation or possible destruction of
the internal switch contact can occur.
AB
AB
BS
WA
AB
W
TS
is the wiper resistance.
, is available in 5 kΩ, 10 kΩ, and 80 kΩ and has 64 tap points
is the wiper resistance at bottom scale.
is the wiper resistance at top scale.
is the end-to-end resistance.
is the end-to-end resistance.
starts at the maximum resistance value and decreases as the
AD5116
R
R
R
R
R
WB
WB
AW
AW
AW
(
(

D


D
R
)
R
R
)
operates in rheostat mode when only two terminals

A
B
BS
TS

AB
Figure 42. Rheostat Mode Configuration
64
D
64

64
R

W

W
R
D
AB


R
R
AB
W
A
B

R
W
W
A
B
Bottom scale
From 0 to 64
Bottom scale
From 0 to 63
Data Sheet
W
Top scale
WA
(1)
(2)
(3)
(4)
(5)
.