Detailed Description

Each potentiometer consists of 255 fixed resistors in

256 different tap points on the resistor string. The

MAX5403/MAX5404/MAX5405 require nine bits to pro-

gram the wiper position. The 1st bit is an address code,

allowing one or the other potentiometers to be selected

for programming. The potentiometers are programmed

independently of each other.

The MAX5403/MAX5404/MAX5405 use a 3-wire serial

data interface to control the wiper tap position. This

write-only interface contains three inputs: Chip Select

(CS), Data In (DIN), and Data Clock (SCLK). When CS

is taken low, data from the DIN pin is synchronously

loaded into the serial shift register on each rising edge

Dual 256-Tap, Low-Drift,

Digital Potentiometers in 10-µMAX

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7

Pin Description

PIN

NAME

FUNCTION

1

GND

Ground

Low Terminal of Resistor B

High Terminal of Resistor B

Wiper Terminal of Resistor B

5

CS

SPI Chip Select

6

DIN

SPI Serial Data Input

7

SCLK

SPI Clock Input

Power Supply, +2.7V to +5.5V. Connect a 0.1

µF capacitor to GND.

Wiper Terminal of Resistor A

10

Low Terminal of Resistor A

GND

DIN

SCLK

9-BIT

SHIFT

REGISTER

R

8-BIT

LATCH

R

8-BIT

LATCH

R

SR

DECODE

CS

8

8

8

256

256

POR

DECODE

DECODE

MAX5403

MAX5404

MAX5405

Figure 1. MAX5403/MAX5404/MAX5405 Functional Diagram: 2-Terminal Variable Resistor and 3-Terminal Potentiometers in 10-µMAX

Configuration