Datasheet AD5235 (Analog Devices)

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Nonvolatile Memory, Dual 1024-Position Digital Potentiometer Data Sheet AD5235 FEATURES FUNCTIONAL BLOCK DIAGRAM Dual-channel, 1024-position resolution AD5235 ADDR V 25 kΩ, 250 kΩ nominal resistance DD CS DECODE RDAC1 REGISTER Maximum ±8% nominal resistor tolerance error A1 CLK W1 Low temperature coefficient: 35 ppm/°C SERIAL SDI INTERFACE B1 2.7 V to 5 V single supply or ±2.5 V dual supply RDAC1 SDO EEMEM1 SPI-compatible serial interface POWER-ON Nonvolatile memory stores wiper settings PR RESET RDAC2 Power-on refreshed with EEMEM settings REGISTER A2 WP EEMEM W2 Permanent memory write protection RDY CONTROL B2 Resistance tolerance stored in EEMEM EEMEM2 RDAC2 26 bytes extra nonvolatile memory for user-defined VSS information 26 BYTES RTOL* USER EEMEM 1M programming cycles GND 100-year typical data retention
001
*RAB TOLERANCE
02816-
APPLICATIONS
Figure 1.
DWDM laser diode driver, optical supervisory systems
In the scratchpad programming mode, a specific setting can
Mechanical potentiometer replacement
be programmed directly to the RDAC2 register, which sets the
Instrumentation: gain, offset adjustment
resistance between Terminal W and Terminal A and Terminal W
Programmable voltage-to-current conversion
and Terminal B. This setting can be stored into the EEMEM
Programmable filters, delays, time constants
and is restored automatical y to the RDAC register during
Programmable power supply
system power-on.
Low resolution DAC replacement Sensor calibration
The EEMEM content can be restored dynamically or through external PR strobing, and a WP function protects EEMEM
GENERAL DESCRIPTION
contents. To simplify the programming, the independent or The AD5235 is a dual-channel, nonvolatile memory,1 digitally simultaneous linear-step increment or decrement commands control ed potentiometer2 with 1024-step resolution, offering can be used to move the RDAC wiper up or down, one step at guaranteed maximum low resistor tolerance error of ±8%. a time. For logarithmic ±6 dB changes in the wiper setting, the The device performs the same electronic adjustment function left or right bit shift command can be used to double or halve the as a mechanical potentiometer with enhanced resolution, solid RDAC wiper setting. state reliability, and superior low temperature coefficient per- The AD5235 patterned resistance tolerance is stored in the formance. The versatile programming of the AD5235 via an EEMEM. The actual end-to-end resistance can, therefore, be SPI®-compatible serial interface allows 16 modes of operation known by the host processor in readback mode. The host can and adjustment including scratchpad programming, memory execute the appropriate resistance step through a software storing and restoring, increment/decrement, ±6 dB/step log taper routine that simplifies open-loop applications as well as adjustment, wiper setting readback, and extra EEMEM1 for user- precision calibration and tolerance matching applications. defined information such as memory data for other components, look-up table, or system identification information. 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. F Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Tel: 781.329.4700 www.analog.com Trademarks and registered trademarks are the property of their respective owners. Fax: 781.461.3113 ©2004–2012 Analog Devices, Inc. All rights reserved.
Document Outline Features Applications General Description Functional Block Diagram Revision History Specifications Electrical Characteristics—25 kΩ, 250 kΩ Versions Interface Timing and EEMEM Reliability Characteristics—25 kΩ, 250 kΩ Versions Timing Diagrams Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Test Circuits Theory of Operation Scratchpad and EEMEM Programming Basic Operation EEMEM Protection Digital Input and Output Configuration Serial Data Interface Daisy-Chain Operation Terminal Voltage Operating Range Power-Up Sequence Layout and Power Supply Bypassing Advanced Control Modes Linear Increment and Decrement Instructions Logarithmic Taper Mode Adjustment Using to Re-Execute a Previous Command Using Additional Internal Nonvolatile EEMEM Calculating Actual End-to-End Terminal Resistance RDAC Structure Programming the Variable Resistor Rheostat Operation Programming the Potentiometer Divider Voltage Output Operation Programming Examples EVAL-AD5235SDZ Evaluation Kit Applications Information Bipolar Operation from Dual Supplies Gain Control Compensation High Voltage Operation DAC Bipolar Programmable Gain Amplifier 10-Bit Bipolar DAC Programmable Voltage Source with Boosted Output Programmable Current Source Programmable Bidirectional Current Source Programmable Low-Pass Filter Programmable Oscillator Optical Transmitter Calibration with ADN2841 Resistance Scaling Resistance Tolerance, Drift, and Temperature Coefficient Mismatch Considerations RDAC Circuit Simulation Model Outline Dimensions Ordering Guide