Nonvolatile Memory, Dual

1024-Position Digital Potentiometer

AD5235-EP

Rev. 0

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FEATURES

Dual-channel, 1024-position resolution

25 kΩ nominal resistance

Low temperature coefficient: 35 ppm/°C

Nonvolatile memory stores wiper settings

Permanent memory write protection

Wiper setting readback

Resistance tolerance stored in EEMEM

Predefined linear increment/decrement instructions

Predefined ±6 dB/step log taper increment/decrement

instructions

SPI-compatible serial interface

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

26 bytes extra nonvolatile memory for user-defined

information

Power-on refreshed with EEMEM settings

Enhanced Features

Supports defense and aerospace applications (AQEC)

Temperature range: −40°C to +125°C

Controlled manufacturing baseline

1 assembly/test site

1 fabrication site

Enhanced product change notification

Qualification data available on request

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-EP is a dual-channel, nonvolatile memory,1

digitally controlled potentiometer2 with 1024-step resolution.

The device performs the same electronic adjustment function as a

mechanical potentiometer with enhanced resolution, solid state

reliability, and superior low temperature coefficient performance.

The AD5235-EP’s versatile programming 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 adjustment, wiper setting

readback, and extra EEMEM1 for user-defined information such as

memory data for other components, look-up tables, or system

identification information.

FUNCTIONAL BLOCK DIAGRAM

ADDR

DECODE

AD5235-EP

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 scratchpad programming mode, a specific setting can be

programmed directly to the RDAC2 register that sets the 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-EP patterned resistance tolerance is stored in the

EEMEM. Therefore, in readback mode, the host processor can

know the actual end-to-end resistance. 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-EP 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 +125°C.

Full details about this enhanced product, including theory of

operation, register details, and applications information, are

available in the AD5235 data sheet, which should be consulted

in conjunction with this data sheet.