MAX5430 MAXIM [Maxim Integrated Products], MAX5430 Datasheet - Page 5

• Manufacturer Part Number: MAX5430
• Description: +/-15V Digitally Programmable Precision Voltage-Dividers for PGAs
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 1. Simplified Functional Diagram
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%
MAX5431
10
1
2
3
4
5
6
7
8
9
PIN
4R
2R
R
R
H
L
MAX5430
_______________________________________________________________________________________
—
—
8
7
6
5
4
3
2
1
Detailed Description
RATIO = 1
RATIO = 2
RATIO = 4
RATIO = 8
Precision Voltage-Dividers for PGAs
MATCH_H
MATCH_L
NAME
GND
V
V
D1
D0
W
H
DD
L
SS
Positive Power Supply
Matching Resistor High Terminal
Ground
High Terminal of Resistive-Divider
Low Terminal of Resistive-Divider
Matching Resistor Low Terminal
Negative Power Supply
Wiper Terminal of Resistive-Divider
Second Bit Digital Input (MSB) (Table 1)
First Bit Digital Input (LSB) (Table 1)
W
±15V Digitally Programmable
(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
(MAX5431 only). In a gain of 1 configuration, H is inte-
rnally connected to W with a typical resistance of 500Ω.
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.
Table 1. Logic-Control Truth Table
D1
0
0
1
1
DIGITAL INPUTS
FUNCTION
Matching Resistor (MAX5431)
D0
0
1
0
1
Pin Description
GAIN
1
2
4
8
5