Dual, 256-Tap, Nonvolatile, SPI-Interface,

Linear-Taper Digital Potentiometers

10

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This command may affect one potentiometer at a time,

or both simultaneously, depending on the state of A1

and A0. Alternatively, the “write NV register” command

can be used to store the current position of the wiper to

the NV register.

Copy NV Register to Wiper Register (Command 11)

This command (C1, C0 = 11) restores the wiper position

to the previously stored position in the NV register. This

command may affect one potentiometer at a time, or both

simultaneously, depending on the state of A1 and A0.

Nonvolatile Memory

The internal EEPROM consists of a nonvolatile register

that retains the last stored value prior to power-down.

The nonvolatile register is programmed to midscale at

the factory. The nonvolatile memory is guaranteed for

200,000 wiper write cycles and 50 years for wiper data

retention.

Power-Up

Upon power-up, the MAX5487/MAX5488/MAX5489

load the data stored in the nonvolatile wiper register

into the volatile memory register, updating the wiper

position with the data stored in the nonvolatile wiper

register. This initialization period takes 5µs.

Standby

The MAX5487/MAX5488/MAX5489 feature a low-power

standby mode. When the device is not being pro-

grammed, it enters into standby mode and supply cur-

rent drops to 0.5µA (typ).

Applications Information

The MAX5487/MAX5488/MAX5489 are ideal for circuits

requiring digitally controlled adjustable resistance,

such as LCD contrast control (where voltage biasing

adjusts the display contrast), or for programmable fil-

ters with adjustable gain and/or cutoff frequency.

Positive LCD Bias Control

Figures 4 and 5 show an application where the

MAX5487/MAX5488/MAX5489 provide an adjustable,

positive LCD-bias voltage. The op amp provides buffer-

ing and gain to the resistor-divider network made by

the potentiometer (Figure 4) or by a fixed resistor and a

variable resistor (Figure 5).

Programmable Filter

Figure 6 shows the MAX5487/MAX5488/MAX5489 in a

1st-order programmable-filter application. Adjust the gain

Figure 3. Digital-Interface Format

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

SCLK

C1

C0

D7

D6

D5

D4

D3

D2

D1

D0

A1

A0

8

7

6

5

4

3

2

1

C1

C0

A1

A0

DIN

SCLK

CS

B) 8-BIT COMMAND WORD

A) 16-BIT COMMAND/DATA WORD

CS

DIN