Datasheet

MAX5430/MAX5431
±15V Digitally Programmable
Precision Voltage-Dividers for PGAs
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Pin Description
PIN
MAX5431 MAX5430
NAME FUNCTION
18V
DD
Positive Power Supply
2—
MATCH_H
Matching Resistor High Terminal
37GND Ground
46HHigh Terminal of Resistive-Divider
55LLow Terminal of Resistive-Divider
6—
MATCH_L
Matching Resistor Low Terminal
74V
SS
Negative Power Supply
83WWiper Terminal of Resistive-Divider
92D1 Second Bit Digital Input (MSB) (Table 1)
10 1 D0 First Bit Digital Input (LSB) (Table 1)
Detailed Description
The MAX5430/MAX5431 are digitally programmable pre-
cision resistor arrays. These devices have fixed resistor-
dividers with digitally controlled contacts, providing four
precision noninverting gains of 1, 2, 4, and 8 for PGA
applications (see Functional Diagram and Figure 1). The
MAX5430/MAX5431 achieve ratio accuracies of 0.025%
(MAX5430A/MAX5431A), 0.09% (MAX5430B/MAX5431B),
or 0.5% (MAX5430C/MAX5431C).
The end-to-end resistance from H to L is 57kΩ. The
impedance seen at W is designed to be the same 14kΩ
for gain settings 2, 4, and 8, ensuring excellent op amp
input-resistance balance, regardless of gain setting. In
a gain of 1 configuration, H is internally connected to W
with a typical resistance of 500Ω.
Matching Resistor (MAX5431)
The MAX5431 includes a matching resistor to compen-
sate the offset voltage due to the input bias current of
the op amp. The resistance from MATCH_H to
MATCH_L is a fixed matching resistor, equal to the
resistance seen at W for gains of 2, 4, and 8. In the
gain of 1, an internal switch short circuits MATCH_H
and MATCH_L. This internal switch matches the imped-
ance of the switch between H and W.
Figure 1. Simplified Functional Diagram
4R
2R
RATIO = 2
RATIO = 1
R
L
W
H
RATIO = 4
RATIO = 8
R
DIGITAL INPUTS
D1 D0
GAIN
00 1
01 2
10 4
11 8
Table 1. Logic-Control Truth Table