Detailed Description

The MAX5427/MAX5428/MAX5429 are 100k

Ω/50kΩ/

10k

Ω (end-to-end resistance) digitally controlled poten-

tiometers. They have 32 tap positions that are accessible

to the wiper along the resistor array between H and L.

The wiper (W) position is adjusted sequentially through

the tap positions using a simple 2-wire interface. These

digital potentiometers have an optional one-time pro-

grammable feature that sets the POR position of the

wiper. The 2-wire interface can then be disabled, perma-

nently preventing unwanted adjustment.

Digital Interface Operation

The MAX5427/MAX5428/MAX5429 have two modes of

operation when the serial interface is active: increment

mode and decrement mode. The serial interface is only

active when CS is low.

The CS and U/D inputs control the position of the wiper

along the resistor array. When CS transitions from high

to low, the part goes into increment mode if U/D is high

(Figure 2), and into decrement mode if U/D is low

(Figure 3). Once the mode is set, the device remains in

that mode until CS goes high. A low-to-high transition at

the U/D increments or decrements the wiper position

depending on the current mode.

When the CS input transitions to high (when serial inter-

face is inactive) and U/D is low, the wiper increments or

decrements one position. If U/D is high when CS transi-

tions to high, the wiper remains in the same position.

One-Time Programmable, Linear-Taper

Digital Potentiometers

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5

Pin Description

Typical Operating Characteristics (continued)

R-INL ERROR vs. INPUT CODE

(MAX5428)

INPUT CODE (DECIMAL)

25

20

15

10

5

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.10

-0.10

030

R-DNL ERROR vs. INPUT CODE

(MAX5429)

INPUT CODE (DECIMAL)

25

20

15

10

5

-0.020

-0.015

-0.010

-0.005

0

0.005

0.010

0.015

0.020

0.025

-0.025

030

R-INL ERROR vs. INPUT CODE

(MAX5429)

INPUT CODE (DECIMAL)

25

20

15

10

5

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.10

-0.10

030

PIN

NAME

FUNCTION

1

W

Wiper Connection

2

CS

Chip-Select Input. A high-to-low CS transition determines the mode: increment if U/D is high, or

decrement if U/D is low. CS is also used for one-time programming (see the One-Time Programming

section).

Power-Supply Voltage

4

GND

Ground

programming the device. For normal operation, connect to ground or let float.

6U/D

Up/Down Control Input. With CS low, a low-to-high transition increments or decrements the wiper

position.

7

L

Low Terminal of Resistor

8

H

High Terminal of Resistor