Nonvolatile Memory, Dual 1024-Position Digital Potentiometer Data Sheet AD5235 FEATURES FUNCTIONAL BLOCK DIAGRAM Dual-channel, 1024-position resolution AD5235 ADDR V DD RDAC1 CS DECODE 25 k , 250 k nominal resistance REGISTER A1 CLK Maximum 8% nominal resistor tolerance error W1 SERIAL SDI Low temperature coefficient: 35 ppm/C INTERFACE B1 RDAC1 SDO 2.7 V to 5 V single supply or 2.5 V dual supply EEMEM1 SPI-compatible serial interface POWER-ON PR RESET Nonvolatile memory stores wiper settings RDAC2 REGISTER A2 Power-on refreshed with EEMEM settings WP EEMEM W2 CONTROL RDY Permanent memory write protection B2 RDAC2 Resistance tolerance stored in EEMEM EEMEM2 26 bytes extra nonvolatile memory for user-defined V SS 26 BYTES information RTOL* USER EEMEM GND 1M programming cycles 100-year typical data retention *RAB TOLERANCE APPLICATIONS Figure 1. DWDM laser diode driver, optical supervisory systems In the scratchpad programming mode, a specific setting can Mechanical potentiometer replacement 2 be programmed directly to the RDAC 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 automatically to the RDAC register during Programmable power supply system power-on. Low resolution DAC replacement The EEMEM content can be restored dynamically or through Sensor calibration external PR strobing, and a WP function protects EEMEM GENERAL DESCRIPTION contents. To simplify the programming, the independent or 1 simultaneous linear-step increment or decrement commands The AD5235 is a dual-channel, nonvolatile memory, digitally 2 can be used to move the RDAC wiper up or down, one step at controlled potentiometer with 1024-step resolution, offering a time. For logarithmic 6 dB changes in the wiper setting, the guaranteed maximum low resistor tolerance error of 8%. 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 1 adjustment, wiper setting readback, and extra EEMEM for user- precision calibration and tolerance matching applications. defined information such as memory data for other components, The AD5235 is available in a thin, 16-lead TSSOP package. look-up table, or system identification information. The part is guaranteed to operate over the extended industrial temperature range of 40C to +85C. 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Fax: 781.461.3113 20042012 Analog Devices, Inc. All rights reserved. 02816-001AD5235 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Programming the Variable Resistor ......................................... 22 Applications ....................................................................................... 1 Programming the Potentiometer Divider ............................... 22 General Description ......................................................................... 1 Programming Examples ............................................................ 23 Functional Block Diagram .............................................................. 1 EVAL-AD5235SDZ Evaluation Kit .......................................... 23 Revision History ............................................................................... 3 Applications Information .............................................................. 24 Specifications ..................................................................................... 4 Bipolar Operation from Dual Supplies.................................... 24 Electrical Characteristics25 k, 250 k Versions ............... 4 Gain Control Compensation .................................................... 24 Interface Timing and EEMEM Reliability Characteristics High Voltage Operation ............................................................ 24 25 k, 250 k Versions ............................................................... 6 DAC .............................................................................................. 24 Absolute Maximum Ratings ............................................................ 8 Bipolar Programmable Gain Amplifier ................................... 25 ESD Caution .................................................................................. 8 10-Bit Bipolar DAC .................................................................... 25 Pin Configuration and Function Descriptions ............................. 9 Programmable Voltage Source with Boosted Output ........... 25 Typical Performance Characteristics ........................................... 10 Programmable Current Source ................................................ 26 Test Circuits ................................................................................. 14 Programmable Bidirectional Current Source ......................... 26 Theory of Operation ...................................................................... 16 Programmable Low-Pass Filter ................................................ 27 Scratchpad and EEMEM Programming .................................. 16 Programmable Oscillator .......................................................... 27 Basic Operation .......................................................................... 16 Optical Transmitter Calibration with ADN2841 ................... 28 EEMEM Protection .................................................................... 17 Resistance Scaling ...................................................................... 28 Digital Input and Output Configuration................................. 17 Resistance Tolerance, Drift, and Temperature Coefficient Serial Data Interface ................................................................... 17 Mismatch Considerations ......................................................... 29 Daisy-Chain Operation ............................................................. 18 RDAC Circuit Simulation Model ............................................. 29 Terminal Voltage Operating Range .......................................... 18 Outline Dimensions ....................................................................... 30 Advanced Control Modes ......................................................... 20 Ordering Guide .......................................................................... 30 RDAC Structure .......................................................................... 21 Rev. F Page 2 of 32