Dual 256-Position I2C Compatible Digital Potentiometer AD5243/AD5248 FEATURES FUNCTIONAL BLOCK DIAGRAMS 2-channel, 256-position End-to-end resistance: 2.5 k, 10 k, 50 k, and 100 k Compact MSOP-10 (3 mm x 4.9 mm) package Fast settling time: tS = 5 s typ on power-up Full read/write of wiper register Power-on preset to midscale Extra package address decode pins AD0 and AD1 (AD5248 only) Computer software replaces C in factory programming applications Single supply: 2.7 V to 5.5 V Low temperature coefficient: 35 ppm/C Low power: IDD = 6 A max Wide operating temperature: -40C to +125C Evaluation board available A1 W1 B1 A2 W2 B2 VDD WIPER REGISTER 1 WIPER REGISTER 2 GND 04109-0-001 AD5243 SDA PC INTERFACE SCL Figure 1. AD5243 W1 B1 W2 B2 APPLICATIONS Systems calibrations Electronics level settings Mechanical Trimmers(R) replacement in new designs Permanent factory PCB setting Transducer adjustment of pressure, temperature, position, chemical, and optical sensors RF amplifier biasing Automotive electronics adjustment Gain control and offset adjustment VDD RDAC REGISTER 1 RDAC REGISTER 2 GND AD1 SDA SCL ADDRESS DECODE /8 SERIAL INPUT REGISTER AD5248 04109-0-002 AD0 Figure 2. AD5248 GENERAL DESCRIPTION The AD5243 and AD5248 provide a compact 3 mm x 4.9 mm packaged solution for dual 256-position adjustment applications. These devices perform the same electronic adjustment function as a 3-terminal mechanical potentiometer (AD5243) or a 2-terminal variable resistor (AD5248). Available in four different end-to-end resistance values (2.5 k, 10 k, 50 k, and 100 k), these low temperature coefficient devices are ideal for high accuracy and stability variable resistance adjustments. The wiper settings are controllable through the I2C compatible digital interface. The AD5248 has extra package address decode pins AD0 and AD1, allowing multiple parts to share the same I2C 2-wire bus on a PCB. The resistance between the wiper and either endpoint of the fixed resistor varies linearly with respect to the digital code transferred into the RDAC latch.1 Operating from a 2.7 V to 5.5 V power supply and consuming less than 6 A allows for usage in portable battery-operated applications. For applications that program the AD5243/AD5258 at the factory, Analog Devices offers device programming software running on Windows(R) NT/2000/XP operating systems. This software effectively replaces any external I2C controllers, which in turn enhances users' systems time-to-market. An AD5243/ AD5248 evaluation kit and software are available. The kit includes a cable and instruction manual. 1 The terms digital potentiometer, VR, and RDAC are used interchangeably. Rev. 0 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. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved. AD5243/AD5248 TABLE OF CONTENTS Electrical Characteristics--2.5 k Version ................................... 3 ESD Protection ........................................................................... 14 Electrical Characteristics--10 k, 50 k, 100 k Versions ....... 4 Terminal Voltage Operating Range.......................................... 14 Timing Characteristics--All Versions ........................................... 5 Power-Up Sequence ................................................................... 14 Absolute Maximum Ratings............................................................ 6 Layout and Power Supply Bypassing ....................................... 14 ESD Caution.................................................................................. 6 Constant Bias to Retain Resistance Setting............................. 15 Pin Configurations and Function Descriptions ........................... 7 Evaluation Board ........................................................................ 15 Typical Performance Characteristics ............................................. 8 I2C Interface .................................................................................... 16 Test Circuits..................................................................................... 12 I2C Compatible 2-Wire Serial Bus ........................................... 16 Theory of Operation ...................................................................... 13 Outline Dimensions ....................................................................... 19 Programming the Variable Resistor and Voltage.................... 13 Ordering Guide .......................................................................... 19 Programming the Potentiometer Divider ............................... 14 REVISION HISTORY Revision 0: Initial Version Rev. 0 | Page 2 of 20 AD5243/AD5248 ELECTRICAL CHARACTERISTICS--2.5 k VERSION VDD = 5 V 10%, or 3 V 10%; VA = +VDD; VB = 0 V; -40C < TA < +125C; unless otherwise noted. Table 1. Parameter Symbol Conditions DC CHARACTERISTICS--RHEOSTAT MODE Resistor Differential Nonlinearity2 R-DNL RWB, VA = no connect Resistor Integral Nonlinearity2 R-INL RWB, VA = no connect Nominal Resistor Tolerance3 TA = 25C RAB Resistance Temperature Coefficient (RAB/RAB )/T VAB = VDD, wiper = no connect RWB (Wiper Resistance) RWB Code = 0x00, VDD = 5 V DC CHARACTERISTICS--POTENTIOMETER DIVIDER MODE (Specifications Apply to All VRs) Differential Nonlinearity4 DNL Integral Nonlinearity INL Code = 0x80 (VW/VW)/T Voltage Divider Temperature Coefficient Full-Scale Error VWFSE Code = 0xFF Zero-Scale Error VWZSE Code = 0x00 RESISTOR TERMINALS Voltage Range5 VA, VB, VW 6 Capacitance A, B CA, CB f = 1 MHz, measured to GND, Code = 0x80 Capacitance6 W CW f = 1 MHz, measured to GND, Code = 0x80 Shutdown Supply Current7 IA_SD VDD = 5.5 V Common-Mode Leakage ICM VA = VB = VDD/2 DIGITAL INPUTS AND OUTPUTS Input Logic High VIH VDD = 5 V Input Logic Low VIL VDD = 5 V Input Logic High VIH VDD = 3 V Input Logic Low VIL VDD = 3 V Input Current IIL VIN = 0 V or 5 V Input Capacitance6 CIL POWER SUPPLIES Power Supply Range VDD RANGE Supply Current IDD VIH = 5 V or VIL = 0 V Power Dissipation8 PDISS VIH = 5 V or VIL = 0 V, VDD = 5 V Power Supply Sensitivity PSS VDD = 5 V 10%, Code = midscale 9 DYNAMIC CHARACTERISTICS Bandwidth -3 dB BW_2.5 K Code = 0x80 Total Harmonic Distortion THDW VA = 1 V rms, VB = 0 V, f = 1 kHz VW Settling Time tS VA = 5 V, VB = 0 V, 1 LSB error band Resistor Noise Voltage Density eN_WB RWB = 1.25 k, RS = 0 See notes at end of section. Rev. 0 | Page 3 of 20 Min Typ1 Max Unit -2 -6 -20 0.1 0.75 +2 +6 +55 LSB LSB % ppm/C 35 160 200 -1.5 -2 0.1 0.6 15 +1.5 +2 LSB LSB ppm/C -10 0 -2.5 2 0 10 LSB LSB VDD V pF pF A nA GND 45 60 0.01 1 1 2.4 0.8 2.1 0.6 1 5 2.7 3.5 0.02 4.8 0.1 1 3.2 5.5 6 30 0.08 V V V V A pF V A W %/% MHz % s nV/Hz AD5243/AD5248 ELECTRICAL CHARACTERISTICS--10 k, 50 k, 100 k VERSIONS VDD = 5 V 10%, or 3 V 10%; VA = VDD; VB = 0 V; -40C < TA < 125C; unless otherwise noted. Table 2. Parameter Symbol Conditions DC CHARACTERISTICS--RHEOSTAT MODE Resistor Differential Nonlinearity2 R-DNL RWB, VA = no connect Resistor Integral Nonlinearity2 R-INL RWB, VA = no connect Nominal Resistor Tolerance3 TA = 25C RAB Resistance Temperature Coefficient (RAB/RAB )/T VAB = VDD, wiper = no connect RWB (Wiper Resistance) RWB Code = 0x00, VDD =5 V DC CHARACTERISTICS--POTENTIOMETER DIVIDER MODE (Specifications Apply to All VRs) Differential Nonlinearity4 DNL Integral Nonlinearity4 INL Code = 0x80 (VW/VW)/T Voltage Divider Temperature Coefficient Full-Scale Error VWFSE Code = 0xFF Zero-Scale Error VWZSE Code = 0x00 RESISTOR TERMINALS Voltage Range5 VA, VB, VW 6 Capacitance A, B CA, CB f = 1 MHz, measured to GND, Code = 0x80 Capacitance6 W CW f = 1 MHz, measured to GND, Code = 0x80 Shutdown Supply Current7 IA_SD VDD = 5.5 V Common-Mode Leakage ICM VA = VB = VDD/2 DIGITAL INPUTS AND OUTPUTS Input Logic High VIH VDD = 5 V Input Logic Low VIL VDD = 5 V Input Logic High VIH VDD = 3 V Input Logic Low VIL VDD = 3 V Input Current IIL VIN = 0 V or 5 V Input Capacitance CIL POWER SUPPLIES Power Supply Range VDD RANGE Supply Current IDD VIH = 5 V or VIL = 0 V Power Dissipation PDISS VIH = 5 V or VIL = 0 V, VDD = 5 V Power Supply Sensitivity PSS VDD = 5 V 10%, Code = midscale DYNAMIC CHARACTERISTICS Bandwidth -3 dB Total Harmonic Distortion VW Settling Time (10 k/50 k/100 k) Resistor Noise Voltage Density BW RAB = 10 k/50 k/100 k, Code = 0x80 THDW tS eN_WB Min Typ1 Max Unit -1 -2.5 -20 0.1 0.25 +1 +2.5 +20 LSB LSB % ppm/C 35 160 200 -1 -1 0.1 0.3 15 +1 +1 LSB LSB ppm/C -2.5 0 -1 1 0 2.5 LSB LSB VDD V pF pF A nA GND 45 60 0.01 1 1 2.4 0.8 2.1 0.6 1 5 2.7 3.5 0.02 5.5 6 30 0.0 8 V V V V A pF V A W %/% kHz VA = 1 V rms, VB = 0 V, f = 1 kHz, RAB = 10 k VA = 5 V, VB = 0 V, 1 LSB error band 600/100/4 0 0.1 2 RWB = 5 k, RS = 0 9 nV/Hz See notes at end of section. Rev. 0 | Page 4 of 20 % s AD5243/AD5248 TIMING CHARACTERISTICS--ALL VERSIONS VDD = 5V 10%, or 3V 10%; VA = VDD; VB = 0 V; -40C < TA < +125C; unless otherwise noted. Table 3. Parameter Symbol Conditions I2C INTERFACE TIMING CHARACTERISTICS10 (Specifications Apply to All Parts) SCL Clock Frequency fSCL tBUF Bus Free Time between STOP and START t1 tHD;STA Hold Time (Repeated START) t2 After this period, the first clock pulse is generated. tLOW Low Period of SCL Clock t3 tHIGH High Period of SCL Clock t4 tSU;STA Setup Time for Repeated START Condition t5 tHD;DAT Data Hold Time11 t6 tSU;DAT Data Setup Time t7 tF Fall Time of Both SDA and SCL Signals t8 tR Rise Time of Both SDA and SCL Signals t9 tSU;STO Setup Time for STOP Condition t10 Min 0 1.3 0.6 Typ1 Max Unit 400 kHz s s 1.3 0.6 0.6 0.9 100 300 300 0.6 See notes at end of section. NOTES 1 Typical specifications represent average readings at 25C and VDD = 5 V. Resistor position nonlinearity error R-INL is the deviation from an ideal value measured between the maximum resistance and the minimum resistance wiper positions. R-DNL measures the relative step change from ideal between successive tap positions. Parts are guaranteed monotonic. 3 VAB = VDD, wiper (VW) = no connect. 4 INL and DNL are measured at VW with the RDAC configured as a potentiometer divider similar to a voltage output D/A converter. VA = VDD and VB = 0 V. DNL specification limits of 1 LSB maximum are guaranteed monotonic operating conditions. 5 Resistor terminals A, B, W have no limitations on polarity with respect to each other. 6 Guaranteed by design and not subject to production test. 7 Measured at the A terminal. The A terminal is open circuited in shutdown mode. 8 PDISS is calculated from (IDD x VDD). CMOS logic level inputs result in minimum power dissipation. 9 All dynamic characteristics use VDD = 5 V. 10 See timing diagrams for locations of measured values. 11 The maximum tHD:DAT must be met only if the device does not stretch the low period (tLOW) of the SCL signal. 2 Rev. 0 | Page 5 of 20 s s s s ns ns ns s AD5243/AD5248 ABSOLUTE MAXIMUM RATINGS TA = 25C, unless otherwise noted. Table 4. Parameter VDD to GND VA, VB, VW to GND Terminal Current, Ax to Bx, Ax to Wx, Bx to Wx1 Pulsed Continuous Digital Inputs and Output Voltage to GND Operating Temperature Range Maximum Junction Temperature (TJMAX) Storage Temperature Lead Temperature (Soldering, 10 sec) Thermal Resistance2 JA: MSOP-10 Value -0.3 V to +7 V VDD 20 mA 5 mA 0 V to 7 V -40C to +125C 150C -65C to +150C 300C 230C/W Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 1 Maximum terminal current is bounded by the maximum current handling of the switches, maximum power dissipation of the package, and maximum applied voltage across any two of the A, B, and W terminals at a given resistance. 2 Package power dissipation = (TJMAX - TA)/JA. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. 0 | Page 6 of 20 AD5243/AD5248 10 W1 B1 1 10 W1 A1 2 9 B2 AD0 2 9 B2 W2 3 AD5248 8 AD1 GND 4 TOP VIEW 7 SDA 6 SCL W2 3 AD5243 8 A2 GND 4 TOP VIEW 7 SDA 6 SCL VDD 5 04109-0-027 B1 1 VDD 5 Figure 3. AD5243 Pin Configuration 04109-0-028 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS Figure 4. AD5248 Pin Configuration Table 5. AD5243 Pin Function Descriptions Table 6. AD5248 Pin Function Descriptions Pin No. 1 2 3 4 5 6 Mnemonic B1 A1 W2 GND VDD SCL Pin No. 1 2 Mnemonic B1 AD0 3 4 5 6 W2 GND VDD SCL 7 8 9 10 SDA A2 B2 W1 7 8 SDA AD1 9 10 B2 W1 Description B1 Terminal. A1 Terminal. W2 Terminal. Digital Ground. Positive Power Supply. Serial Clock Input. Positive edge triggered. Serial Data Input/Output. A2 Terminal. B2 Terminal. W1 Terminal. Rev. 0 | Page 7 of 20 Description B1 Terminal. Programmable Address Bit 0 for Multiple Package Decoding. W2 Terminal. Digital Ground. Positive Power Supply. Serial Clock Input. Positive edge triggered. Serial Data Input/Output. Programmable Address Bit 1 for Multiple Package Decoding. B2 Terminal. W1 Terminal. AD5243/AD5248 TYPICAL PERFORMANCE CHARACTERISTICS 2.0 0.5 TA = 25C RAB = 10k 1.0 VDD = 2.7V 0.5 0 VDD = 5.5V -0.5 RAB = 10k 0.4 POTENTIOMETER MODE DNL (LSB) -1.0 -1.5 0.3 0.2 0.1 VDD = 2.7V; TA = -40C, +25C, +85C, +125C 0 -0.1 -0.2 -0.3 32 64 96 128 160 192 224 256 CODE (DECIMAL) -0.5 04109-0-030 0 0 32 128 160 192 224 256 Figure 8. DNL vs. Code vs. Temperature 0.5 1.0 TA = 25C RAB = 10k 0.3 0.2 VDD = 2.7V 0.1 0 -0.1 -0.2 VDD = 5.5V -0.3 TA = 25C RAB = 10k 0.8 POTENTIOMETER MODE INL (LSB) 0.4 -0.4 0.6 0.4 VDD = 5.5V 0.2 0 VDD = 2.7V -0.2 -0.4 -0.6 -0.8 0 32 64 96 128 160 192 224 256 CODE (DECIMAL) -1.0 04109-0-031 -0.5 0 32 64 96 128 160 192 224 256 CODE (DECIMAL) Figure 6. R-DNL vs. Code vs. Supply Voltages 04109-0-034 RHEOSTAT MODE DNL (LSB) 96 CODE (DECIMAL) Figure 5. R-INL vs. Code vs. Supply Voltages Figure 9. INL vs. Code vs. Supply Voltages 0.5 0.5 RAB = 10k 0.4 TA = 25C RAB = 10k 0.3 POTENTIOMETER MODE DNL (LSB) 0.4 VDD = 5.5V TA = -40C, +25C, +85C, +125C 0.2 0.1 0 -0.1 VDD = 2.7V TA = -40C, +25C, +85C, +125C -0.2 -0.3 -0.4 0.3 0.2 0.1 VDD = 2.7V 0 -0.1 VDD = 5.5V -0.2 -0.3 -0.4 -0.5 0 32 64 96 128 160 192 CODE (DECIMAL) 224 256 04109-0-032 POTENTIOMETER MODE INL (LSB) 64 04109-0-033 -0.4 -2.0 Figure 7. INL vs. Code vs. Temperature -0.5 0 32 64 96 128 160 192 224 CODE (DECIMAL) Figure 10. DNL vs. Code vs. Supply Voltages Rev. 0 | Page 8 of 20 256 04109-0-035 RHEOSTAT MODE INL (LSB) 1.5 AD5243/AD5248 2.0 4.50 RAB = 10k 1.0 0.5 0 VDD = 5.5V TA = -40C, +25C, +85C, +125C -0.5 -1.0 -1.5 0 32 64 96 128 160 192 224 256 CODE (DECIMAL) 3.00 2.25 VDD = 2.7V, VA = 2.7V 1.50 VDD = 5.5V, VA = 5.0V 0.75 0 -40 04109-0-036 -2.0 3.75 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) Figure 11. R-INL vs. Code vs. Temperature Figure 14. Zero-Scale Error vs. Temperature 0.5 10 RAB = 10k 0.4 0.3 0.2 IDD, SUPPLY CURRENT (A) RHEOSTAT MODE DNL (LSB) -25 04109-0-039 ZSE, ZERO-SCALE ERROR (LSB) RHEOSTAT MODE INL (LSB) RAB = 10k VDD = 2.7V TA = -40C, +25C, +85C, +125C 1.5 VDD = 2.7V, 5.5V; TA = -40C, +25C, +85C, +125C 0.1 0 -0.1 -0.2 VDD = 5V 1 VDD = 3V -0.3 32 64 96 128 160 192 224 256 CODE (DECIMAL) 0.1 -40 -7 26 59 92 Figure 15. Supply Current vs. Temperature Figure 12. R-DNL vs. Code vs. Temperature 120 2.0 RAB = 10k RAB = 10k RHEOSTAT MODE TEMPCO (ppm/C) 1.0 0.5 0 VDD = 5.5V, VA = 5.0V -0.5 VDD = 2.7V, VA = 2.7V -1.0 -1.5 -25 -10 5 20 35 50 65 80 95 TEMPERATURE (C) 110 125 04109-0-038 FSE, FULL-SCALE ERROR (LSB) 1.5 -2.0 -40 125 TEMPERATURE (C) 100 80 60 VDD = 2.7V TA = -40C TO +85C, -40C TO +125C 40 VDD = 5.5V TA = -40C TO +85C, -40C TO +125C 20 0 -20 0 32 64 96 128 160 192 224 CODE (DECIMAL) Figure 16. Rheostat Mode Tempco RWB/T vs. Code Figure 13. Full-Scale Error vs. Temperature Rev. 0 | Page 9 of 20 256 04109-0-041 0 04109-0-037 -0.5 04109-0-040 -0.4 AD5243/AD5248 0 RAB = 10k 0x80 -6 40 0x40 -12 30 0x20 -18 VDD = 2.7V TA = -40C TO +85C, -40C TO +125C GAIN (dB) 20 10 0 0x10 -24 0x08 -30 0x04 -36 0x02 -42 -10 0x01 VDD = 5.5V TA = -40C TO +85C, -40C TO +125C -48 -20 0 32 64 96 128 160 192 224 256 CODE (DECIMAL) -60 1k 1M Figure 20. Gain vs. Frequency vs. Code, RAB = 50 k 0 0 0x80 -6 0x80 -6 0x40 -12 0x40 -12 0x20 -18 -24 GAIN (dB) 0x08 0x04 -30 0x20 -18 0x10 -36 0x10 -24 0x08 -30 0x04 -36 0x02 0x01 -42 0x02 -42 -48 -54 -54 -60 10k 100k 1M 10M FREQUENCY (Hz) -60 1k 10k 100k 1M FREQUENCY (Hz) Figure 18. Gain vs. Frequency vs. Code, RAB = 2.5 k 04109-0-046 0x01 -48 04109-0-043 Figure 21. Gain vs. Frequency vs. Code, RAB = 100 k 0 0 0x80 -6 -12 0x40 -18 0x20 -6 -12 100k 60kHz -18 50k 120kHz GAIN (dB) 0x10 -24 0x08 -30 0x04 -36 0x02 0x01 -42 -24 -36 -42 -48 -54 -54 -60 10k 100k FREQUENCY (Hz) 1M 04109-0-044 -48 1k 10k 570kHz 2.5k 2.2MHz -30 Figure 19. Gain vs. Frequency vs. Code, RAB = 10 k -60 1k 10k 100k 1M FREQUENCY (Hz) Figure 22. -3 dB Bandwidth @ Code = 0x80 Rev. 0 | Page 10 of 20 10M 04109-0-047 GAIN (dB) 100k FREQUENCY (Hz) Figure 17. Potentiometer Mode Tempco VWB/T vs. Code GAIN (dB) 10k 04109-0-045 -54 -30 04109-0-042 POTENTIOMETER MODE TEMPCO (ppm/C) 50 AD5243/AD5248 10 1 VDD = 5.5V VW2 0.1 VDD = 2.7V 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 DIGITAL INPUT VOLTAGE (V) 4.0 4.5 5.0 04109-0-052 0.01 04109-0-051 VW1 Figure 26. Analog Crosstalk Figure 23. IDD vs. Input Voltage VW VW 04109-0-048 04109-0-053 SCL VW2 VW VW1 SCL 04109-0-050 Figure 27. Midscale Glitch, Code 0x80 to 0x7F Figure 24. Digital Feedthrough 04109-0-049 IDD, SUPPLY CURRENT (mA) TA = 25C Figure 28. Large Signal Settling Time Figure 25. Digital Crosstalk Rev. 0 | Page 11 of 20 AD5243/AD5248 TEST CIRCUITS Figure 29 through Figure 35 illustrate the test circuits that define the test conditions used in the product specification tables. V+ = VDD 1LSB = V+/2N DUT W VIN AD8610 OFFSET GND 04109-0-003 VMS -15V 2.5V Figure 33. Test Circuit for Gain vs. Frequency Figure 29. Test Circuit for Potentiometer Divider Nonlinearity Error (INL, DNL) NO CONNECT IW A W 04109-0-004 Figure 34. Test Circuit for Incremental On Resistance NC DUT IW = VDD/RNOMINAL DUT VW A VDD B RW = [VMS1 - VMS2]/IW VMS1 W GND 04109-0-005 W A W V+ B VMS PSRR (dB) = 20 LOG VDD VMS% PSS (%/%) = VDD% VMS ( ) 04109-0-006 V+ = VDD 10% VCM NC = NO CONNECT Figure 35. Test Circuit for Common-Mode Leakage Current Figure 31. Test Circuit for Wiper Resistance DUT ICM B NC VA 0.1V VSS TO VDD Figure 30. Test Circuit for Resistor Position Nonlinearity Error (Rheostat Operation; R-INL, R-DNL) VMS2 ISW B VMS 0.1V ISW CODE = 0x00 W B A RSW = DUT DUT VOUT 04109-0-009 B B VDD +15V W 04109-0-011 V+ DUT A 04109-0-010 A Figure 32. Test Circuit for Power Supply Sensitivity(PSS, PSSR) Rev. 0 | Page 12 of 20 AD5243/AD5248 THEORY OF OPERATION The AD5243/AD5248 are 256-position digitally controlled variable resistor (VR) devices. The general equation determining the digitally programmed output resistance between W and B is An internal power-on preset places the wiper at midscale during power-on, which simplifies the fault condition recovery at power-up. PROGRAMMING THE VARIABLE RESISTOR AND VOLTAGE Rheostat Operation The nominal resistance of the RDAC between Terminals A and B is available in 2.5 k, 10 k, 50 k, and 100 k. The nominal resistance (RAB) of the VR has 256 contact points accessed by the wiper terminal, plus the B terminal contact. The 8-bit data in the RDAC latch is decoded to select one of the 256 possible settings. A A B B Figure 36. Rheostat Mode Configuration Assuming that a 10 k part is used, the wiper's first connection starts at the B terminal for data 0x00. Because there is a 50 wiper contact resistance, such a connection yields a minimum of 100 (2 x 50 ) resistance between Terminals W and B. The second connection is the first tap point, which corresponds to 139 (RWB = RAB/256 + 2 x RW = 39 + 2 x 50 ) for data 0x01. The third connection is the next tap point, representing 178 (2 x 39 + 2 x 50 ) for data 0x02, and so on. Each LSB data value increase moves the wiper up the resistor ladder until the last tap point is reached at 10,100 (RAB + 2 x RW). A RS D7 D6 D5 D4 D3 D2 D1 D0 D is the decimal equivalent of the binary code loaded in the 8-bit RDAC register. RAB is the end-to-end resistance. RW is the wiper resistance contributed by the on resistance of the internal switch. In summary, if RAB = 10 k and the A terminal is open circuited, the following output resistance RWB is set for the indicated RDAC latch codes. RWB () 9,961 5,060 139 100 Note that, in the zero-scale condition, a finite wiper resistance of 100 is present. Care should be taken to limit the current flow between W and B in this state to a maximum pulse current of no more than 20 mA. Otherwise, degradation or possible destruction of the internal switch contact can occur. Similar to the mechanical potentiometer, the resistance of the RDAC between the Wiper W and Terminal A also produces a digitally controlled complementary resistance, RWA. When these terminals are used, the B terminal can be opened. Setting the resistance value for RWA starts at a maximum value of resistance and decreases as the data loaded in the latch increases in value. The general equation for this operation is RWA (D ) = RS RS Output State Full scale (RAB - 1 LSB + RW) Midscale 1 LSB Zero scale (wiper contact resistance) 256 - D x RAB + 2 x RW 256 RDAC (2) For RAB = 10 k and the B terminal open circuited, the following output resistance RWA is set for the indicated RDAC latch codes. W Table 8. Codes and Corresponding RWA Resistance RS B 04109-0-013 LATCH AND DECODER (1) where: D (Dec) 255 128 1 0 W 04109-0-012 W B D x RAB + 2 x RW 256 Table 7. Codes and Corresponding RWB Resistance A W RWB (D ) = D (Dec) 255 128 1 0 Figure 37. AD5243 Equivalent RDAC Circuit Rev. 0 | Page 13 of 20 RWA () 139 5,060 9,961 10,060 Output State Full scale Midscale 1 LSB Zero scale AD5243/AD5248 Typical device-to-device matching is process lot dependent and may vary by up to 30%. Because the resistance element is processed in thin film technology, the change in RAB with temperature has a very low 35 ppm/C temperature coefficient. 340 GND 04109-0-015 LOGIC Figure 39. ESD Protection of Digital Pins PROGRAMMING THE POTENTIOMETER DIVIDER The digital potentiometer easily generates a voltage divider at wiper-to-B and wiper-to-A proportional to the input voltage at A to B. Unlike the polarity of VDD to GND, which must be positive, voltage across A to B, W to A, and W to B can be at either polarity. A 04109-0-014 VO B Figure 40. ESD Protection of Resistor Terminals TERMINAL VOLTAGE OPERATING RANGE The AD5243/AD5248 VDD and GND power supply defines the boundary conditions for proper 3-terminal digital potentiometer operation. Supply signals present on Terminals A, B, and W that exceed VDD or GND are clamped by the internal forward biased diodes (see Figure 41). VI W GND 04109-0-016 A, B, W Voltage Output Operation VDD Figure 38. Potentiometer Mode Configuration A D 256 - D VW (D ) = VA + VB 256 256 (3) A more accurate calculation, which includes the effect of wiper resistance, VW, is VW (D ) = R (D ) RWB (D ) VA + WA VB RAB RAB (4) Operation of the digital potentiometer in the divider mode results in a more accurate operation overtemperature. Unlike the rheostat mode, the output voltage is dependent mainly on the ratio of the internal resistors RWA and RWB and not the absolute values. Therefore, the temperature drift reduces to 15 ppm/C. ESD PROTECTION All digital inputs are protected with a series of input resistors and parallel Zener ESD structures, shown in Figure 39 and Figure 40. This applies to the digital input pins SDA, SCL, AD0, and AD1 (AD5248 only). W B GND 04109-0-017 If ignoring the effect of the wiper resistance for approximation, connecting the A terminal to 5 V and the B terminal to ground produces an output voltage at the wiper-to-B starting at 0 V up to 1 LSB less than 5 V. Each LSB of voltage is equal to the voltage applied across terminal AB divided by the 256 positions of the potentiometer divider. The general equation defining the output voltage at VW with respect to ground for any valid input voltage applied to terminals A and B is Figure 41. Maximum Terminal Voltages Set by VDD and GND POWER-UP SEQUENCE Because the ESD protection diodes limit the voltage compliance at Terminals A, B, and W (see Figure 41), it is important to power VDD/GND before applying any voltage to Terminals A, B, and W; otherwise, the diode is forward biased such that VDD is powered unintentionally and may affect the rest of the user's circuit. The ideal power-up sequence is in the following order: GND, VDD, digital inputs, and then VA, VB, and VW. The relative order of powering VA, VB, VW, and the digital inputs is not important as long as they are powered after VDD/GND. LAYOUT AND POWER SUPPLY BYPASSING It is good practice to employ compact, minimum lead length layout design. The leads to the inputs should be as direct as possible with a minimum conductor length. Ground paths should have low resistance and low inductance. Similarly, it is also good practice to bypass the power supplies with quality capacitors for optimum stability. Supply leads to the device should be bypassed with disk or chip ceramic capacitors of 0.01 F to 0.1 F. Low ESR 1 F to 10 F tantalum or electrolytic capacitors should also be applied at the supplies to minimize any transient disturbance and low frequency ripple (see Figure 42). Note that the digital ground should also be joined remotely to the analog ground at one point to minimize the ground bounce. Rev. 0 | Page 14 of 20 AD5243/AD5248 VDD C3 10F + This demonstrates that constantly biasing the potentiometer is not an impractical approach. Most portable devices do not require the removal of batteries for the purpose of charging. Although the resistance setting of the AD5243/AD5248 is lost when the battery needs replacement, such events occur rather infrequently such that this inconvenience is justified by the lower cost and smaller size offered by the AD5243/AD5248. If and when total power is lost, the user should be provided with a means to adjust the setting accordingly. VDD C1 0.1F AD5243 04109-0-018 GND Figure 42. Power Supply Bypassing EVALUATION BOARD CONSTANT BIAS TO RETAIN RESISTANCE SETTING For users who desire nonvolatility but cannot justify the additional cost for the EEMEM, the AD5243/AD5248 may be considered as low cost alternatives by maintaining a constant bias to retain the wiper setting. The AD5243/AD5248 are designed specifically with low power in mind, which allows low power consumption even in battery-operated systems. The graph in Figure 43 demonstrates the power consumption from a 3.4 V 450 mAhr Li-Ion cell phone battery, which is connected to the AD5243/AD5248. The measurement over time shows that the device draws approximately 1.3 A and consumes negligible power. Over a course of 30 days, the battery is depleted by less than 2%, the majority of which is due to the intrinsic leakage current of the battery itself. An evaluation board, along with all necessary software, is available to program the AD5243/AD5248 from any PC running Windows 98/2000/XP. The graphical user interface, as shown in Figure 44, is straightforward and easy to use. More detailed information is available in the user manual, which comes with the board. 110% 108% TA = 25C 104% 102% 100% 98% Figure 44. AD5243 Evaluation Board Software 96% The AD5243/AD5248 start at midscale upon power-up. To increment or decrement the resistance, the user may simply move the scrollbars on the left. To write any specific value, the user should use the bit pattern in the upper screen and press the Run button. The format of writing data to the device is shown in Table 9. To read the data out from the device, the user can simply press the Read button. The format of the read bits is shown in Table 10. 94% 92% 90% 0 5 10 15 DAYS 20 25 Figure 43. Battery Operating Life Depletion 30 04109-0-019 BATTERY LIFE DEPLETED 106% Rev. 0 | Page 15 of 20 AD5243/AD5248 I2C INTERFACE I2C COMPATIBLE 2-WIRE SERIAL BUS The 2-wire I2C serial bus protocol operates as follows: 1. The master initiates data transfer by establishing a START condition, which is when a high-to-low transition on the SDA line occurs while SCL is high (see Figure 46). The following byte is the slave address byte, which consists of the slave address followed by an R/W bit (this bit determines whether data is read from or written to the slave device). The AD5243 has a fixed slave address byte, while the AD5248 has two configurable address bits AD0 and AD1 (see Table 9). 3. Note that the channel of interest is the one that is previously selected in the write mode. In the case where users need to read the RDAC values of both channels, they need to program the first channel in the write mode and then change to the read mode to read the first channel value. After that, they need to change back to the write mode with the second channel selected and read the second channel value in the read mode again. It is not necessary for users to issue the Frame 3 data byte in the write mode for subsequent readback operation. Users should refer to Figure 48 and Figure 49 for the programming format. The slave whose address corresponds to the transmitted address responds by pulling the SDA line low during the ninth clock pulse (this is termed the acknowledge bit). At this stage, all other devices on the bus remain idle while the selected device waits for data to be written to or read from its serial register. If the R/W bit is high, the master reads from the slave device. On the other hand, if the R/W bit is low, the master writes to the slave device. 2. In the write mode, the second byte is the instruction byte. The first bit (MSB) of the instruction byte is the RDAC subaddress select bit. A Logic Low selects Channel 1 and a Logic High selects Channel 2. In the read mode, the data byte follows immediately after the acknowledgment of the slave address byte. Data is transmitted over the serial bus in sequences of nine clock pulses (a slight difference with the write mode, eight data bits are followed by an acknowledge bit). Similarly, the transitions on the SDA line must occur during the low period of SCL and remain stable during the high period of SCL (see Figure 48 and Figure 49). 4. The second MSB, SD, is a shutdown bit. A logic high causes an open circuit at Terminal A while shorting the wiper to Terminal B. This operation yields almost 0 in rheostat mode or 0 V in potentiometer mode. It is important to note that the shutdown operation does not disturb the contents of the register. When brought out of shutdown, the previous setting is applied to the RDAC. Also, during shutdown, new settings can be programmed. When the part is returned from shutdown, the corresponding VR setting is applied to the RDAC. The remainder of the bits in the instruction byte are don't care bits (see Table 9). After acknowledging the instruction byte, the last byte in write mode is the data byte. Data is transmitted over the serial bus in sequences of nine clock pulses (eight data bits followed by an acknowledge bit). The transitions on the SDA line must occur during the low period of SCL and remain stable during the high period of SCL (see Figure 46 and Figure 47). Rev. 0 | Page 16 of 20 After all data bits have been read or written, a STOP condition is established by the master. A STOP condition is defined as a low-to-high transition on the SDA line while SCL is high. In write mode, the master pulls the SDA line high during the tenth clock pulse to establish a STOP condition (see Figure 46 and Figure 47). In read mode, the master issues a no acknowledge for the ninth clock pulse (that is, the SDA line remains high). The master then brings the SDA line low before the tenth clock pulse, which goes high to establish a STOP condition (see Figure 48 and Figure 49). A repeated write function gives the user flexibility to update the RDAC output a number of times after addressing and instructing the part only once. For example, after the RDAC has acknowledged its slave address and instruction bytes in the write mode, the RDAC output updates on each successive byte. If different instructions are needed, the write/read mode has to start again with a new slave address, instruction, and data byte. Similarly, a repeated read function of the RDAC is also allowed. AD5243/AD5248 Table 9. Write Mode AD5243 S 0 1 0 1 1 1 1 W A A0 SD Slave Address Byte X X X X X X A D7 D6 D5 D4 Instruction Byte D3 D2 D1 D0 A P A P Data Byte AD5248 S 0 1 0 1 1 AD1 AD0 W A A0 SD Slave Address Byte X X X X X X A D7 D6 D5 D4 Instruction Byte D3 D2 D1 D0 Data Byte Table 10. Read Mode AD5243 S 0 1 0 1 1 1 1 R A D7 D6 D5 D4 Slave Address Byte D3 D2 D1 D0 A P Data Byte AD5248 0 1 0 1 1 AD1 AD0 R A D7 D6 D5 D4 Slave Address Byte LEGEND S = Start condition. P = Stop condition. A = Acknowledge. X = Don't care. W = Write. AD0, AD1 = Package pin programmable address bits. D3 D2 D1 D0 A Data Byte R = Read. A0 = RDAC subaddress select bit. SD = Shutdown connects wiper to B terminal and open circuits A terminal. It does not change contents of wiper register. D7, D6, D5, D4, D3, D2, D1, D0 = Data bits. t8 t6 t2 t9 SCL t4 t3 t2 t8 t7 t10 t5 t9 04109-0-021 SDA t1 P S S P Figure 45. I2C Interface Detailed Timing Diagram 9 1 1 9 1 9 SCL SDA 0 1 0 1 1 1 1 R/W A0 SD X X X X ACK BY AD5243 START BY MASTER FRAME 1 SLAVE ADDRESS BYTE X X D7 D6 D5 D4 D3 FRAME 2 INSTRUCTION BYTE Figure 46. Writing to the RDAC Register--AD5243 Rev. 0 | Page 17 of 20 D2 D1 D0 ACK BY AD5243 ACK BY AD5243 FRAME 3 DATA BYTE 04109-0-022 S STOP BY MASTER P AD5243/AD5248 9 1 1 9 1 9 SDA 0 1 0 1 AD1 AD0 R/W 1 A0 SD X X X X X X ACK BY AD5248 START BY MASTER D7 D6 D5 D4 D3 D2 D1 FRAME 2 INSTRUCTION BYTE FRAME 1 SLAVE ADDRESS BYTE D0 ACK BY AD5248 ACK BY AD5248 04109-0-023 SCL STOP BY MASTER FRAME 3 DATA BYTE Figure 47. Writing to the RDAC Register--AD5248 1 9 1 9 SCL 0 1 0 1 1 1 1 R/W D7 D6 D5 D4 D3 D2 D1 ACK BY AD5243 START BY MASTER D0 NO ACK BY MASTER FRAME 2 RDAC REGISTER FRAME 1 SLAVE ADDRESS BYTE STOP BY MASTER 04109-0-024 SDA Figure 48. Reading Data from a Previously Selected RDAC Register in Write Mode--AD5243 9 1 1 9 SCL 0 1 0 1 1 AD1 AD0 R/W D7 D6 D5 D4 D3 D2 D1 START BY MASTER D0 NO ACK BY MASTER ACK BY AD5248 FRAME 2 RDAC REGISTER FRAME 1 SLAVE ADDRESS BYTE STOP BY MASTER 04109-0-025 SDA Figure 49. Reading Data from a Previously Selected RDAC Register in Write Mode--AD5248 Multiple Devices on One Bus (Applies Only to AD5248) RP SDA MASTER SCL 5V 5V SDA SCL SDA SCL 5V SDA SCL SCL AD1 AD1 AD1 AD0 AD0 AD0 AD0 AD5248 AD5248 AD5248 AD5248 Figure 50. Multiple AD5248 Devices on One I2C Bus Rev. 0 | Page 18 of 20 SDA AD1 04109-0-026 Figure 50 shows four AD5248 devices on the same serial bus. Each has a different slave address, because the states of their AD0 and AD1 pins are different. This allows each device on the bus to be written to or read from independently. The master device output bus line drivers are open-drain pull-downs in a fully I2C compatible interface. 5V RP AD5243/AD5248 OUTLINE DIMENSIONS 3.00 BSC 10 6 4.90 BSC 3.00 BSC 1 5 PIN 1 0.50 BSC 0.95 0.85 0.75 0.15 0.00 1.10 MAX 0.27 0.17 SEATING PLANE 0.23 0.08 8 0 0.80 0.60 0.40 COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-187BA Figure 51. 10-Lead Mini Small Outline Package [MSOP] (RM-10) Dimensions shown in millimeters ORDERING GUIDE Model AD5243BRM2.5 AD5243BRM2.5-RL7 AD5243BRM10 AD5243BRM10-RL7 AD5243BRM50 AD5243BRM50-RL7 AD5243BRM100 AD5243BRM100-RL7 AD5243EVAL AD5248BRM2.5 AD5248BRM2.5-RL7 AD5248BRM10 AD5248BRM10-RL7 AD5248BRM50 AD5248BRM50-RL7 AD5248BRM100 AD5248BRM100-RL7 AD5248EVAL RAB 2.5 k 2.5 k 10 k 10 k 50 k 50 k 100 k 100 k See Note 1 2.5 k 2.5 k 10 k 10 k 50 k 50 k 100 k 100 k See Note 1 Temperature -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C Package Description MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 Evaluation Board MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 MSOP-10 Evaluation Board 1 Package Option RM-10 RM-10 RM-10 RM-10 RM-10 RM-10 RM-10 RM-10 Branding D0L D0L D0M D0M D0N D0N D0P D0P RM-10 RM-10 RM-10 RM-10 RM-10 RM-10 RM-10 RM-10 D1F D1F D1G D1G D1H D1H D1J D1J The evaluation board is shipped with the 10 k RAB resistor option; however, the board is compatible with all available resistor value options. Rev. 0 | Page 19 of 20 AD5243/AD5248 NOTES Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. (c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04109-0-1/04(0) Rev. 0 | Page 20 of 20