Nonvolatile Memory, Dual
1024-Position Digital Potentiometer
AD5235
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Dual-channel, 1024-position resolution
25 kΩ, 250 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
AD5235
V
ADDR
DECODE
DD
RDAC1
REGISTER
CS
CLK
SDI
A1
W1
SERIAL
INTERFACE
B1
RDAC1
SDO
EEMEM1
POWER-ON
RESET
PR
RDAC2
REGISTER
A2
WP
EEMEM
CONTROL
W2
RDY
B2
RDAC2
EEMEM2
SPI-compatible serial interface
V
SS
26 BYTES
USER EEMEM
3 V to 5 V single supply or 2.5 V dual supply
26 bytes extra nonvolatile memory for user-defined
information
100-year typical data retention, TA = 55°C
Power-on refreshed with EEMEM settings
RTOL*
GND
*RAB TOLERANCE
Figure 1.
In the scratchpad programming mode, a specific setting can
be programmed directly to the RDAC2 register, which sets the
resistance between Terminal W and Terminal A and Terminal W
and Terminal ꢀ. This setting can be stored into the EEMEM
and is restored automatically to the RDAC register during
system power-on.
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
The EEMEM content can be restored dynamically or through
PR
WP
external
strobing, and a
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 dꢀ changes in the wiper setting, the
left or right bit shift command can be used to double or halve the
RDAC wiper setting.
Low resolution DAC replacement
Sensor calibration
GENERAL DESCRIPTION
The AD5235 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
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 dꢀ/step log taper adjustment, wiper
setting readback, and extra EEMEM1 for user-defined information
such as memory data for other components, look-up table, or
system identification information.
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.
Rev. C
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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