Nonvolatile Memory, Dual

1024-Position Digital Potentiometer

Data Sheet

AD5235

Rev. F

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FEATURES

Dual-channel, 1024-position resolution

25 kΩ, 250 kΩ nominal resistance

Maximum ±8% nominal resistor tolerance error

Low temperature coefficient: 35 ppm/°C

2.7 V to 5 V single supply or ±2.5 V dual supply

SPI-compatible serial interface

Nonvolatile memory stores wiper settings

Power-on refreshed with EEMEM settings

Permanent memory write protection

Resistance tolerance stored in EEMEM

26 bytes extra nonvolatile memory for user-defined

information

1M programming cycles

100-year typical data retention

APPLICATIONS

DWDM laser diode driver, optical supervisory systems

Mechanical potentiometer replacement

Instrumentation: gain, offset adjustment

Programmable voltage-to-current conversion

Programmable filters, delays, time constants

Programmable power supply

Low resolution DAC replacement

Sensor calibration

GENERAL DESCRIPTION

The AD5235 is a dual-channel, nonvolatile memory,1 digitally

controlled potentiometer2 with 1024-step resolution, offering

guaranteed maximum low resistor tolerance error of ±8%.

The device performs the same electronic adjustment function

as a mechanical potentiometer with enhanced resolution, solid

state reliability, and superior low temperature coefficient per-

formance. The versatile programming of the AD5235 via an

SPI®-compatible serial interface allows 16 modes of operation

and adjustment including scratchpad programming, memory

storing and restoring, increment/decrement, ±6 dB/step log taper

defined information such as memory data for other components,

look-up table, or system identification information.

FUNCTIONAL BLOCK DIAGRAM

ADDR

DECODE

AD5235

RDAC1

SERIAL

INTERFACE

CS

CLK

SDI

SDO

PR

WP

RDY

RDAC1

REGISTER

EEMEM1

RDAC2

REGISTER

EEMEM2

26 BYTES

RTOL*

USER EEMEM

POWER-ON

RESET

W1

B1

RDAC2

W2

B2

A1

A2

GND

EEMEM

CONTROL

*RAB TOLERANCE

Figure 1.

In the scratchpad programming mode, a specific setting can

resistance between Terminal W and Terminal A and Terminal W

and Terminal B. This setting can be stored into the EEMEM

and is restored automatically to the RDAC register during

system power-on.

The EEMEM content can be restored dynamically or through

external PR strobing, and a WP function protects EEMEM

contents. To simplify the programming, the independent or

simultaneous linear-step increment or decrement commands

can be used to move the RDAC wiper up or down, one step at

a time. For logarithmic ±6 dB changes in the wiper setting, the

left or right bit shift command can be used to double or halve the

RDAC wiper setting.

The AD5235 patterned resistance tolerance is stored in the

EEMEM. The actual end-to-end resistance can, therefore, be

known by the host processor in readback mode. The host can

execute the appropriate resistance step through a software

routine that simplifies open-loop applications as well as

precision calibration and tolerance matching applications.

The AD5235 is available in a thin, 16-lead TSSOP package.

The part is guaranteed to operate over the extended industrial

temperature range of −40°C to +85°C.

1

The terms nonvolatile memory and EEMEM are used interchangeably.

2

The terms digital potentiometer and RDAC are used interchangeably.