数字电位器MAX5422-MAX5424.pdf

General DescriptionThe MAX5422/MAX5423/MAX5424 nonvolatile,linear-taper,digital potentiometers perform the function of amechanical potentiometer,but replace the mechanicswith a simple 3-wire SPI-compatible digital interface.Each device performs the same function as a discretepotentiometer or variable resistor and has 256 tap points.The devices feature an internal,nonvolatile EEPROMused to store the wiper position for initialization duringpower-up.The 3-wire SPI-compatible serial interfaceallows communication at data rates up to 5MHz,mini-mizing board space and reducing interconnection com-plexity in many applications.The MAX5422/MAX5423/MAX5424 provide three nomi-nal resistance values:50k(MAX5422),100k(MAX5423),or 200k(MAX5424).The nominal resistortemperature coefficient is 35ppm/C end-to-end andonly 5ppm/C ratiometric.This makes the devices idealfor applications requiring a low-temperature-coefficientvariable resistor,such as low-drift,programmable gain-amplifier circuit configurations.The MAX5422/MAX5423/MAX5424 are available in a3mm x 3mm 8-pin TDFN package,and are specifiedover the extended-40C to+85C temperature range.ApplicationsMechanical Potentiometer ReplacementLow-Drift Programmable Gain AmplifiersAudio Volume ControlLiquid-Crystal Display(LCD)Contrast ControlLow-Drift Programmable FiltersFeatures Wiper Position Stored in Nonvolatile Memory(EEPROM)and Recalled Upon Power-Up orInterface Command 3mm x 3mm x 0.8mm TDFN Package 35ppm/C End-to-End Resistance TemperatureCoefficient 5ppm/C Ratiometric Temperature Coefficient 50k,100k,and 200k Resistor Values 5MHz SPI-Compatible Serial Interface 500nA(typ)Static Supply Current Single-Supply Operation:+2.7V to+5.25V 256 Tap Positions 0.5 LSB DNL in Voltage-Divider Mode 0.5 LSB INL in Voltage-Divider ModeMAX5422/MAX5423/MAX5424256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers_ Maxim Integrated Products1Ordering Information/Selector Guide19-3371;Rev 0;7/04For pricing,delivery,and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-4642,or visit Maxims website at www.maxim-.EVALUATION KITAVAILABLEPARTTEMP RANGEEND-TO-ENDRESISTANCE(k)PIN-PACKAGETOP MARKMAX5422ETA-40C to+85C508 TDFN-EP*AIJMAX5423ETA-40C to+85C1008 TDFN-EP*AIIMAX5424ETA-40C to+85C2008 TDFN-EP*AIHVDDSCLKDINGND12345WH678LTDFN(3mm x 3mm)TOP VIEWCSMAX5422MAX5423MAX5424Pin ConfigurationWLSPIINTERFACE256-POSITIONDECODERVDDGNDSCLK8-BITNVMEMORY8-BITLATCH8-BITSHIFTREGISTERPORH88256DINCSMAX5422MAX5423MAX5424Functional DiagramSPI is a trademark of Motorola,Inc.*EP=Exposed pad.MAX5422/MAX5423/MAX5424256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers2_ABSOLUTE MAXIMUM RATINGSELECTRICAL CHARACTERISTICS(VDD=+2.7V to+5.25V,H=VDD,L=GND,TA=-40C to+85C.Typical values are at VDD=+5.0V,TA=+25C,unless otherwise noted.)Stresses beyond those listed under“Absolute Maximum Ratings”may cause permanent damage to the device.These are stress ratings only,and functionaloperation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied.Exposure toabsolute maximum rating conditions for extended periods may affect device reliability.VDDto GND.-0.3V to+6.0VAll Other Pins to GND.-0.3V to(VDD+0.3V)Maximum Continuous Current into H,L,and WMAX5422.1.3mAMAX5423.0.6mAMAX5424.0.3mAContinuous Power Dissipation(TA=+70C)8-Pin TDFN(derate 24.4mW/C above+70C).1951mWOperating Temperature Range.-40C to+85CJunction Temperature.+150CStorage Temperature Range.-60C to+150CLead Temperature(soldering,10s).+300CPARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSDC PERFORMANCE(VOLTAGEDIVIDER MODE)ResolutionN256TapsIntegral NonlinearityINL(Note 1)0.5LSBDifferential NonlinearityDNL(Note 1)0.5LSBEnd-to-End ResistanceTemperature CoefficientTCR35ppm/CRatiometric ResistanceTemperature Coefficient5ppm/CMAX5422-0.6MAX5423-0.3Full-Scale ErrorMAX5424-0.15LSBMAX54220.7MAX54230.35Zero-Scale ErrorMAX54240.18LSBDC PERFORMANCE(VARIABLE-RESISTOR MODE)VDD=3V3.0Integral Nonlinearity(Note 2)INLVDD=5V1.5LSBVDD=3V,MAX5422,-40C TA +85C,guaranteed monotonic-1.0+2.0VDD=3V,MAX5422,0C TA +85C,guaranteed monotonic-1.0+1.2VDD=3V,MAX54231.0VDD=3V,MAX54241.0Differential Nonlinearity(Note 2)DNLVDD=5V1.0LSBDC PERFORMANCE(RESISTOR CHARACTERISTICS)Wiper ResistanceRWVDD=3V to 5.25V(Note 3)325675Wiper CapacitanceCW10pFMAX542237.55062.5MAX542375100125End-to-End ResistanceMAX5424150200250kMAX5422/MAX5423/MAX5424256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers_3ELECTRICAL CHARACTERISTICS(continued)(VDD=+2.7V to+5.25V,H=VDD,L=GND,TA=-40C to+85C.Typical values are at VDD=+5.0V,TA=+25C,unless otherwise noted.)PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSDIGITAL INPUTS(CS,DIN,SCLK)VDD=3.4V to 5.25V2.4Input High Voltage(Note 4)VIHVDD 3.4V0.7 xVDDVInput Low VoltageVILVDD=2.7V to 5.25V(Note 4)0.8VInput Leakage CurrentIIN0.11AInput CapacitanceCIN5pFDYNAMIC CHARACTERISTICSMAX5422100MAX542350Wiper-3dB Bandwidth(Note 5)MAX542425kHzNONVOLATILE MEMORY RELIABILITYData RetentionTA=+85C50YearsTA=+25C200,000EnduranceTA=+85C50,000StoresPOWER SUPPLYSupply VoltageVDD2.705.25VStandby CurrentIDDDigital inputs=VDD or GND,TA=+25C0.51 AProgramming CurrentIPGDuring nonvolatile write to memory;digitalinputs=VDD or GND(Note 6)200 400 ATIMING CHARACTERISTICS(VDD=+2.7V to+5.25V,H=VDD,L=GND,TA=-40C to+85C.Typical values are at VDD=+5.0V,TA=+25C,unless otherwisenoted.See Figure 1.)(Note 7)PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSANALOG SECTIONMAX5422400MAX5423600Wiper Settling Time(Note 8)tSMAX54241000nsDIGITAL SECTIONSCLK FrequencyfSCLK5MHzSCLK Clock PeriodtCP200nsSCLK Pulse-Width HightCH80nsSCLK Pulse-Width LowtCL80nsCS Fall to SCLK Rise SetuptCSS80nsSCLK Rise to CS Rise HoldtCSH0nsDIN to SCLK SetuptDS50nsDNL vs.TAP POSITIONMAX5422 toc01TAP POSITIONDNL(LSB)224192128160649632-0.20-0.15-0.10-0.0500.050.100.150.200.25-0.250256VOLTAGE-DIVIDER MODEINL vs.TAP POSITIONMAX5422 toc02TAP POSITIONINL(LSB)224192128160649632-0.20-0.15-0.10-0.0500.050.100.150.200.25-0.250256VOLTAGE-DIVIDER MODERESISTANCE()1002003004005006007000WIPER RESISTANCE vs.TAP POSITIONMAX5422 toc03TAP POSITION2241921281606496320256VDD=2.7VISRC=50ATypical Operating Characteristics(VDD=5.0V,TA=+25C,unless otherwise noted.)MAX5422/MAX5423/MAX5424256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers4_TIMING CHARACTERISTICS(continued)(VDD=+2.7V to+5.25V,H=VDD,L=GND,TA=-40C to+85C.Typical values are at VDD=+5.0V,TA=+25C,unless otherwisenoted.See Figure 1.)(Note 7)PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSDIN Hold after SCLKtDH0nsSCLK Rise to CS Fall DelaytCS020nsCS Rise to SCLK Rise HoldtCS180nsCS Pulse-Width HightCSW200nsWrite NV Register Busy TimetBUSY12msNote 1:The DNL and INL are measured with the potentiometer configured as a voltage-divider with H=VDDand L=GND.Thewiper terminal is unloaded and measured with a high-input-impedance voltmeter.Note 2:The DNL and INL are measured with the potentiometer configured as a variable resistor.H is unconnected and L=GND.For the 5V condition,the wiper terminal is driven with a source current of 80A for the 50k configuration,40A for the100k configuration,and 20A for the 200k configuration.For the 3V condition,the wiper terminal is driven with a sourcecurrent of 40A for the 50k configuration,20A for the 100k,and 10A for the 200k configuration.Note 3:The wiper resistance is measured using the source currents given in Note 2.For operation to VDD=2.7V,see MaximumWiper Resistance vs.Temperature in the Typical Operating Characteristics.Note 4:The device draws higher supply current when the digital inputs are driven with voltages between(VDD-0.5V)and(GND+0.5V).See Supply Current vs.Digital Input Voltage in the Typical Operating Characteristics.Note 5:Wiper at midscale with a 10pF load(DC measurement).L=GND;an AC source is applied to H;and the W output is mea-sured.A 3dB bandwidth occurs when the AC W/H value is 3dB lower than the DC W/H value.Note 6:The programming current operates only during power-up and NV writes.Note 7:Digital timing is guaranteed by design and characterization,and is not production tested.Note 8:Wiper-settling time is the worst-case 0%to 50%rise-time measured between consecutive wiper positions.H=VDD,L=GND,and the wiper terminal is unloaded and measured with a 10pF oscilloscope probe.MAX5422/MAX5423/MAX5424256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers_5WIPER TRANSIENT AT POWER-ON4s/divVDD1V/divW1V/divCL=10pFTAP=128H=VDDMAX5422 toc04-1.00.4-0.6-0.8-0.200.20.40.60.81.0-4010-15356085END-TO-END RESISTANCE%CHANGE vs.TEMPERATUREMAX5422toc05TEMPERATURE(C)END-TO-END RESISTANCE%CHANGESTANDBY SUPPLY CURRENTvs.TEMPERATUREMAX5422 toc06TEMPERATURE(C)SUPPLY CURRENT(A)603510-150.10.20.30.40.50.60.70.80.91.00-4085VDD=5.25VVDD=4.0VVDD=3.0VVDD=2.7VMAXIMUM WIPER RESISTANCE vs.TEMPERATUREMAX5422 toc07TEMPERATURE(C)RESISTANCE()603510-151002003004005006007000-4085VDD=5.25VVDD=4.5VVDD=3.0VVDD=2.7VTypical Operating Characteristics(continued)(VDD=5.0V,TA=+25C,unless otherwise noted.)SUPPLY CURRENTvs.DIGITAL INPUT VOLTAGEMAX5422 toc08DIGITAL INPUT VOLTAGE(V)SUPPLY CURRENT(A)3421100200300400500600005THD+N RESPONSEMAX5422 toc09FREQUENCY(Hz)THD+N(%)10k1k1000.0010.010.11101000.000110100k1:1 RATIO20Hz TO 20kHz BANDPASSINL vs.TAP POSITION(MAX5422)MAX5422 toc10TAP POSITIONINL(LSB)224192160128966432-0.500.51.01.52.0-1.00256VARIABLE-RESISTOR MODEVDD=2.7VISRC=50AMAX5422/MAX5423/MAX5424256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers6_INL vs.TAP POSITION(MAX5424)MAX5422 toc12TAP POSITIONINL(LSB)224192160128966432-0.500.51.01.52.0-1.00256VARIABLE-RESISTOR MODEVDD=2.7VISRC=10ADNL vs.TAP POSITION(MAX5422)MAX5422 toc13TAP POSITIONDNL(LSB)224192160128966432-0.2-0.100.10.20.3-0.30256VARIABLE-RESISTOR MODEDNL vs.TAP POSITION(MAX5423)MAX5422 toc14TAP POSITIONDNL(LSB)224192160128966432-0.2-0.100.10.20.3-0.30256VARIABLE-RESISTOR MODE-0.2-0.100.10.20.30.40.5-0.3DNL vs.TAP POSITION(MAX5424)MAX5422 toc15TAP POSITIONDNL(LSB)2241921601289664320256VARIABLE-RESISTOR MODETypical Operating Characteristics(continued)(VDD=5.0V,TA=+25C,unless otherwise noted.)INL vs.TAP POSITION(MAX5423)MAX5422 toc11TAP POSITIONINL(LSB)224192160128966432-0.500.51.01.52.0-1.00256VARIABLE-RESISTOR MODEVDD=2.7VISRC=20ADetailed DescriptionThe MAX5422/MAX5423/MAX5424 contain a resistorarray with 255 resistive elements.The MAX5422 has atotal end-to-end resistance of 50k;the MAX5423 hasan end-to-end resistance of 100k;and the MAX5424has an end-to-end resistance of 200k.TheMAX5422/MAX5423/MAX5424 allow access to the high,low,and wiper terminals for a standard voltage-dividerconfiguration.H,L,and W can be connected in anydesired configuration as long as their voltages fallbetween GND and VDD.A simple,3-wire,SPI serial interface moves the wiperamong the 256 tap points.The nonvolatile memorystores the wiper position and recalls the stored wiperposition upon power-upThe nonvolatile memory isguaranteed for 50 years for wiper data retention and upto 200,000 wiper store cycles.Analog CircuitryThe MAX5422/MAX5423/MAX5424 consist of a resistorarray with 255 resistive elements;256 tap points areaccessible to the wiper,W,along the resistor stringbetween H and L.Select the wiper tap point by pro-gramming the potentiometer through the 3-wire(SPI)interface.Eight data bits,and a control byte programthe wiper position.The H and L terminals of theMAX5422/MAX5423/MAX5424 are similar to the twoend terminals of a mechanical potentiometer.TheMAX5422/MAX5423/MAX5424 feature power-on resetcircuitry that loads the wiper position from the non-volatile memory at power-up.Digital InterfaceThe MAX5422/MAX5423/MAX5424 use a 3-wire,SPI-compatible,serial data interface(Figure 1 and 2).Thiswrite-only interface contains three inputs:chip-selectMAX5422/MAX5423/MAX5424256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers_7PINNAMEFUNCTION1VDDPower-Supply Input.Bypass VDD with a 0.1F capacitor from VDD to GND.2SCLKSerial-Interface Clock Input3DINSerial-Interface Data Input4CSActive-Low Digital-Input Chip Select5GNDGround6LLow Terminal.The voltage at L can be greater than or less than the voltage at H.Current can flow into orout of L.7WWiper Terminal8HHigh Terminal.The voltage at H can be greater than or less than the voltage at L.Current can flow into orout of H.EPExposed Pad.The exposed pad is not internally connected.Connect to GND or leave floating.Pin DescriptionSCLKCSDINtCS0tDStCLtCHtDHtCPtCSHtCS1tCSWtCSSFigure 1.Digital Interface and Timing DiagramMAX5422/MAX5423/MAX5424(CS),data clock(SCLK),and data in(DIN).Drive CSlow to enable the serial interface and clock data syn-chronously into the shift register on each SCLK risingedge.The WRITE commands(C1,C0=00 or 01)require 16clock cycles to clock in the command and data(Figure2a).The COPY commands(C1,C0=10,11)can useeither eight clock cycles to transfer the command bits(Figure 2b)or 16 clock cycles with 8 data bits that aredisregarded by the device(Figure 2a).After loading data into the shift register,drive CS highto latch the data into the appropriate potentiometercontrol register and disable the serial interface.KeepCS low during the entire serial-data stream to avoidcorruption of the data.The serial-data timing for the potentiometer is shown inFigures 1 and 2.256-Tap,Nonvolatile,SPI-Interface,Digital Potentiometers8_CLOCK EDGE12345678910111213141516Bit nameC1C0D7D6D5D4D3D2D1D0Write wiper register00000000D7D6D5D4D3D2D1D0Write NV register00010000D7D6D5D4D3D2D1D0Copy wiper register to NVregister00100000Copy NV register to wiperregister00110000Table 1.Register Map12345678910111213141516D7D6D5D4D3D2D1D0C1C0SCLKDINA)16-BIT COMMAND/DATA WORD12345678C1C0SCLKDINB)8-BIT COMMAND WORDCSCSFigure 2.Digital-Interface FormatWrite Wiper RegisterData written to this register(C1,C0=00)controls thewiper positions.The 8 data bits(D7 to D0)indicate theposition of the wiper.For example,if DIN=0000 0000,the wiper moves to the position closest to L.If DIN=1111 1111,the wiper moves closest to H.This command writes data to the volatile randomaccess memory(RAM),leaving the NV registersunchanged.When the device powers up,the datastored in the NV registers transfers to the volatile wiperregister,moving the wiper to the stored position.Write NV RegisterThe“write NV register”command(C1,C0=01)storesthe position of the wipers to the NV registers for use atpower-up.Alternatively,the“copy wiper register to NVregister”command writes to the NV register.Writing to theNV registers,does not affect the position of the wipers.Copy Wiper Register to NV RegisterThe“copy wiper register to NV register”command(C1,C0=10)stores the current position of the wiper to theNV register for use at power-up.Copy NV Register to Wiper RegisterThe“copy NV register to wiper register”(C1,C0=11)restores the wiper position to the current value stored inthe NV register.Standby ModeThe MAX5422/MAX5423/MAX5424 feature a low-powerstandby mode.When the device is not being pro-grammed,it enters into standby mode and supply cur-rent drops to 0.5A(typ).Nonvolatile MemoryThe internal EEPROM consists of a nonvolatile registerthat ret