EVAL-AD5235EBZ

Manufacturer Part NumberEVAL-AD5235EBZ
DescriptionBOARD EVALUATION FOR AD5235
ManufacturerAnalog Devices Inc
EVAL-AD5235EBZ datasheet
 

Specifications of EVAL-AD5235EBZ

Main PurposeDigital PotentiometerUtilized Ic / PartAD5235
Lead Free Status / RoHS StatusLead free / RoHS CompliantSecondary Attributes-
Embedded-Primary Attributes-
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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,
2
controlled potentiometer
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
adjustment, wiper setting readback, and extra EEMEM
defined information such as memory data for other components,
look-up table, or system identification information.
1
The terms nonvolatile memory and EEMEM are used interchangeably.
2
The terms digital potentiometer and RDAC are used interchangeably.
Rev. D
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
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.
Nonvolatile Memory, Dual
1024-Position Digital Potentiometer
FUNCTIONAL BLOCK DIAGRAM
ADDR
CS
DECODE
CLK
SERIAL
SDI
INTERFACE
SDO
POWER-ON
PR
RESET
WP
EEMEM
CONTROL
RDY
*RAB TOLERANCE
In the scratchpad programming mode, a specific setting can
be programmed directly to the RDAC
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
1
simultaneous linear-step increment or decrement commands
digitally
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
1
for user-
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
AD5235
AD5235
V
RDAC1
REGISTER
A1
W1
B1
RDAC1
EEMEM1
RDAC2
REGISTER
A2
W2
B2
RDAC2
EEMEM2
V
26 BYTES
RTOL*
USER EEMEM
GND
Figure 1.
2
register, which sets the
www.analog.com
©2004–2011 Analog Devices, Inc. All rights reserved.
DD
SS

EVAL-AD5235EBZ Summary of contents

  • Page 1

    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 single supply or ±2.5 V dual supply SPI-compatible serial interface Nonvolatile memory stores wiper ...

  • Page 2

    ... Daisy-Chain Operation ............................................................. 18 Terminal Voltage Operating Range.......................................... 18 Advanced Control Modes ......................................................... 20 RDAC Structure.......................................................................... 21 Programming the Variable Resistor......................................... 22 Programming the Potentiometer Divider............................... 22 Programming Examples ............................................................ 23 EVAL-AD5235SDZ Evaluation Kit.......................................... 23 Applications Information .............................................................. 24 Bipolar Operation from Dual Supplies.................................... 24 Gain Control Compensation .................................................... 24 High Voltage Operation ............................................................ 24 DAC.............................................................................................. 24 Bipolar Programmable Gain Amplifier................................... 25 10-Bit Bipolar DAC ...

  • Page 3

    ... Changes to Pin 5, Pin 13, Pin 14 Descriptions ..............................9 Changes to Typical Performance Characteristics Section .........10 Changes to Table 7 ..........................................................................19 Changes to Table 9 ..........................................................................21 Changes to Rheostat Operation Section, Table 12, Table 13 .....22 Changes to Table 16, Table 19, and EVAL-AD5235SDZ Evaluation Kit Section ....................................................................23 Changes to RDAC Circuit Simulation Model Section ...............29 Updated Outline Dimensions........................................................30 Changes to Ordering Guide...........................................................30 4/09— ...

  • Page 4

    AD5235 SPECIFICATIONS ELECTRICAL CHARACTERISTICS—25 kΩ, 250 kΩ VERSIONS These specifications apply to 25 kΩ versions with a date code 1108 or ...

  • Page 5

    Parameter POWER SUPPLIES Single-Supply Power Range Dual-Supply Power Range Positive Supply Current Negative Supply Current EEMEM Store Mode Current 7 EEMEM Restore Mode Current 8 Power Dissipation 5 Power Supply Sensitivity 5, 9 DYNAMIC CHARACTERISTICS Bandwidth Total Harmonic Distortion V ...

  • Page 6

    AD5235 INTERFACE TIMING AND EEMEM RELIABILITY CHARACTERISTICS—25 kΩ, 250 kΩ VERSIONS Guaranteed by design and not subject to production test. See the Timing Diagrams section for the location of measured values. All input control voltages are specified with t = ...

  • Page 7

    Timing Diagrams CLK CPOL = 1 HIGH OR LOW SDI t 8 B24* SDO t 14 RDY *THE EXTRA BIT THAT IS NOT DEFINED IS NORMALLY THE LSB OF THE CHARACTER PREVIOUSLY TRANSMITTED. THE CPOL = 1 ...

  • Page 8

    AD5235 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 3. Parameter V to GND GND GND ...

  • Page 9

    PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Table 4. Pin Function Descriptions Pin No. Mnemonic Description 1 CLK Serial Input Register Clock. Shifts in one bit at a time on positive clock edges. 2 SDI Serial Data Input. Shifts in one bit ...

  • Page 10

    AD5235 TYPICAL PERFORMANCE CHARACTERISTICS 0.20 +85°C +25°C 0.15 –40°C 0.10 0.05 0 –0.05 –0.10 –0.15 –0.20 0 200 400 600 DIGITAL CODE Figure 5. INL vs. Code −40°C, +25°C, +85°C Overlay 0.16 +85°C +25°C 0.14 –40°C ...

  • Page 11

    CODE (Decimal) Figure 11. Wiper On Resistance vs. Code ...

  • Page 12

    AD5235 3 0 – 250kΩ AB – 12kHz –3dB f –3dB – ±2. rms MIDSCALE –12 1k 10k FREQUENCY (Hz) Figure 17. −3 dB Bandwidth ...

  • Page 13

    TIME (µs) Figure 23. Midscale Glitch Energy (5V/DIV) CLK (5V/DIV) SDI (5V/DIV) I (2mA/DIV) DD Figure 24. I vs. Time ...

  • Page 14

    AD5235 TEST CIRCUITS Figure 27 to Figure 37 define the test conditions used in the Specifications section. NC DUT CONNECT Figure 27. Resistor Position Nonlinearity Error (Rheostat Operation; R-INL, R-DNL) ...

  • Page 15

    DUT W V GND CONNECT Figure 35. Common-Mode Leakage Current RDAC1 RDAC2 OUT ...

  • Page 16

    AD5235 THEORY OF OPERATION The AD5235 digital potentiometer is designed to operate as a true variable resistor. The resistor wiper position is determined by the RDAC register contents. The RDAC register acts as a scratchpad register, allowing unlimited changes of ...

  • Page 17

    EEMEM PROTECTION The write protect ( WP ) pin disables any changes to the scratchpad register contents, except for the EEMEM setting, which can still be restored using Instruction 1, Instruction 8, and the PR pulse. Therefore, WP can be ...

  • Page 18

    AD5235 DAISY-CHAIN OPERATION The serial data output pin (SDO) serves two purposes. It can be used to read the contents of the wiper setting and EEMEM values using Instruction 10 and Instruction 9, respectively. The remaining instructions (Instruction 0 to ...

  • Page 19

    In Table 6, command bits are C0 to C3, address bits are A0 to A3, Data Bit D0 to Data Bit D9 are applicable to RDAC, and D0 to D15 are applicable to EEMEM. Table 6. 24-Bit Serial Data-Word MSB ...

  • Page 20

    AD5235 ADVANCED CONTROL MODES The AD5235 digital potentiometer includes a set of user programming features to address the wide number of applications for these universal adjustment devices. Key programming features include the following: • Scratchpad programming to any desirable values ...

  • Page 21

    Using CS to Re-Execute a Previous Command Another subtle feature of the AD5235 is that a subsequent CS strobe, without clock and data, repeats a previous command. Using Additional Internal Nonvolatile EEMEM The AD5235 contains additional user EEMEM registers for ...

  • Page 22

    AD5235 PROGRAMMING THE VARIABLE RESISTOR Rheostat Operation The nominal resistance of the RDAC between Terminal A and Terminal available with 25 kΩ and 250 kΩ with AB 1024 positions (10-bit resolution). The final digits of the ...

  • Page 23

    ... Table 20. Reading Back Wiper Settings SDI 0xB00200 0xC0XXXX 0xA0XXXX 0xXXXXXX EVAL-AD5235SDZ EVALUATION KIT Analog Devices, Inc., offers a user-friendly EVAL-AD5235SDZ evaluation kit that can be controlled conjunction with the no programming languages or skills are needed. Rev Page SDO Action 0xXXXXXX Restores the EEMEM1 value to the RDAC1 register ...

  • Page 24

    AD5235 APPLICATIONS INFORMATION BIPOLAR OPERATION FROM DUAL SUPPLIES The AD5235 can be operated from ±2.5 V dual supplies, which enable control of ground referenced ac signals or bipolar operation. AC signals as high as V and V can be applied ...

  • Page 25

    BIPOLAR PROGRAMMABLE GAIN AMPLIFIER For applications requiring bipolar gain, Figure 51 shows one implementation. Digital Potentiometer U1 sets the adjustment range; the wiper voltage (V ) can, therefore, be programmed W2 between V and − given U2 setting. ...

  • Page 26

    AD5235 PROGRAMMABLE CURRENT SOURCE A programmable current source can be implemented with the circuit shown in Figure 54. + (2.048V + SLEEP OUTPUT B REF191 C1 1µF GND ...

  • Page 27

    PROGRAMMABLE LOW-PASS FILTER In analog-to-digital conversions (ADCs common to include an antialiasing filter to band limit the sampling signal. Therefore, the dual-channel AD5235 can be used to construct a second-order Sallen-Key low-pass filter, as shown in Figure 56. ...

  • Page 28

    AD5235 OPTICAL TRANSMITTER CALIBRATION WITH ADN2841 The AD5235, together with the multirate 2.7 Gbps laser diode driver, ADN2841, forms an optical supervisory system in which the dual digital potentiometers can be used to set the laser average optical power and ...

  • Page 29

    RESISTANCE TOLERANCE, DRIFT, AND TEMPERATURE COEFFICIENT MISMATCH CONSIDERATIONS In rheostat mode operation, such as gain control, the tolerance mismatch between the digital potentiometer and the discrete resistor can cause repeatability issues among various systems (see Figure 62). Because of the ...

  • Page 30

    ... Temperature Package Range Description −40°C to +85°C 16-Lead TSSOP −40°C to +85°C 16-Lead TSSOP −40°C to +85°C 16-Lead TSSOP −40°C to +85°C 16-Lead TSSOP Evaluation Board Rev Page 0.75 0.60 0.45 Package Ordering Option Quantity Branding RU-16 96 ...

  • Page 31

    NOTES Rev Page AD5235 ...

  • Page 32

    AD5235 NOTES ©2004–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D02816-0-4/11(D) Rev Page ...