AD421 data sheet - Analog Devices

1 FUNCTIONAL BLOCK DIAGRAMLOCALOSCILLATORSWITCHEDCURRENTSOU RCESANDFILTERINGBANDGAPREFERENCEREF IN(+ )REF OUT1(+ )REF OUT2(+ )LVVCCDRIVECOMPBOOSTLOOPRTNC1 C2 C3 COMLATCHCLOCKDATA40 16-BITSIGMA-DELTA DAC75k 134k 121k 80k AD421 INPUT SHIFTREGISTERDAC LATCHPOWER-ONRESETREV. CInformation furnished by Analog Devices is believed to be accurate andreliable. However, no responsibility is assumed by Analog Devices for itsuse, nor for any infringements of patents or other rights of third partieswhich may result from its use. No license is granted by implication orotherwise under any patent or patent rights of Analog mA to 20 mA Current OutputHART Compatible16-Bit Resolution and Monotonicity Integral Nonlinearity5 V or 3 V Regulator V and V Precision Reference750 A Quiescent Current maxProgrammable Alarm Current CapabilityFlexible High Speed Serial Interface16-Lead SOIC and PDIP PackagesLoop-Powered4 mA to 20 mA DACAD421 PRODUCT HIGHLIGHTS1.

2 The AD421 is a single chip, high performance, low costsolution for generating 4 mA to 20 mA signals for smartindustrial control The AD421 s regulated supply voltage can be used to powerany additional circuits in the transmitter. The regulatedoutput value is pin selectable as either +3 V, + V or +5 The AD421 s on-chip references can provide a precisionreference voltage to other Devices in the system. This refer - ence voltage can be either + V or + The AD421 is fully compatible with standard HART cir-cuitry or other similar FSK With the addition of a single discrete transistor, the AD421can be operated from VCC + 2 V min to a maximum of thebreakdown voltage of the pass The AD421 converts the digital data to current with 16-bitresolution and monotonicity.

3 Full-scale settling time to typically occurs within 8 The AD421 features a programmable alarm current capabil-ity that allows the transmitter to send out of range currents toindicate a transducer is a registered trademark of the HART DESCRIPTIONThe AD421 is a complete, loop-powered, digital to 4 mA to20 mA converter, designed to meet the needs of smart trans-mitter manufacturers in the Industrial Control industry. It pro-vides a high precision, fully integrated, low cost solution in acompact 16-lead package. The AD421 is ideal for extending theresolution of smart 4 mA to 20 mA transmitters at very low AD421 includes a selectable regulator that is used to poweritself and other Devices in the transmitter.

4 This regulator pro-vides either a +5 V, + V or +3 V regulated output part also contains + V and + V precision AD421 thus eliminates the need for a discrete regulatorand voltage reference . The only external components requiredare a number of passive components and a pass transistor tospan large loop AD421 can be used with standard HART FSK protocolcommunication circuitry without any degradation in specifiedperformance. The high speed serial interface is capable of oper-ating at 10 Mbps and allows for simple connection to com-monly-used microprocessors and microcontrollers via a standardthree-wire serial sigma-delta architecture of the DAC guarantees 16-bitmonotonicity while the integral nonlinearity for the AD421 is The part provides a zero scale 4 mA output currentwith offset error and a 20 mA full-scale output currentwith gain AD421 is available in a 16-lead, inch-wide, plastic DIPand in a 16-lead, inch-wide.

5 SOIC package. The part is speci-fied over the industrial temperature range of 40 C to +85 Technology Way, Box 9106, Norwood, MA 02062-9106, : 781/329-4700 World Wide Web Site: : 781/326-8703 Analog Devices , Inc., 2000 DAC SPECIFICATIONSP arameterB Versions2 UnitsConditions/CommentsACCURACYR esolution16 BitsMonotonicity16 Bits minIntegral Nonlinearity of FS maxFS = Full-Scale Output CurrentOffset (4 mA) @ +25 C4 of FS maxVCC = 5 VOffset Drift 25ppm of FS/ C max Includes On-Chip reference DriftTotal Output Error (20 mA)

6 @ +25 C4 of FS maxVCC = 5 VTotal Output Drift 50ppm of FS/ C max Includes On-Chip reference DriftVCC Supply Sensitivity50nA/mV max25 nA/mV TypicalVOLTAGE REFERENCEREF OUT2 Output min/V V NominalDrift 40ppm/ C max20 ppm/ C Typical from 40 C to +25 C and ppm/ C Typical from +25 C to +85 CExternally Available minVCC Supply Sensitivity150 V/V max15 V/V TypicalOutput Impedance3 typNoise ( Hz 10 Hz)6 V (p-p) typREF OUT1 Output min/V V Nominal, 100 k Load to COM5 Drift 50ppm/ C max20 ppm/ C Typical from 40 C to +25 C and2 ppm/ C Typical from +25 C to +85 CExternally Available minVCC Supply Sensitivity150 V/V max15 V/V TypicalOutput Impedance3 typNoise ( Hz 10 Hz)4 V (p-p) typREF INInput Resistance40k typDIGITAL INPUTSVIH (Logic 1) VCCV minVIL (Logic 0)

7 VCCV maxIIH 10 A maxVIN = VCCIIL 10 A maxVIN = 0 VData CodingBinaryData Rate10 Mbps maxPOWER SUPPLIESO perating Range+ to + min to V maxFunctional to 7 VQuiescent Current@ VCC = 3 V650 A max475 A Typical@ VCC = 5 V750 A max575 A TypicalNOTES1 The DN25D is available from Supertex, Inc., 1350 Bordeaux Drive, Sunnyvale, CA range is 40 C to +85 max current loop voltage compliance is determined by the pass transistor breakdown voltage and is 350 V for the VCC = 3 V, the transfer function shifts negative by typically.

8 A 16 k resistor connected between COM and LOOPRTN will approximately compensate for the VCCsupply sensitivity in moving from 5 V to 3 V by skewing the gain of the k resistor only required if this reference is being used in application subject to change without LOOP-POWERED SPECIFICATIONSP arameter B Versions2 UnitsConditions/CommentsOUTPUT CHARACTERISTICSC urrent Loop Voltage Compliance3 VCC + 2V min350V maxDN25D Breakdown VoltageFull-Scale Settling Time8ms typSettling Time to , C1 = C2 = 10 nF, C3 = nFOutput Impedance25M typAC Loop Voltage Sensitivity2 A/V typ1200 Hz to 2200 HzVOLTAGE REGULATORO utput Voltage (VCC)3 V min/V max3 V Nominal.

9 LV Pin Connected to V min/V V Nominal. LV Pin Connected Through F to VCC5 V min/V max5 V Nominal. LV Pin Connected to COME xternally Available minAssuming 4 mA Flowing in the LoopLine Regulation1 V/V typLoad Regulation15 V/mA typ 2 (Using DN25D1 as pass transistor as per Figure 3;REF IN = REF OUT2; TA = TMIN to TMAX unless otherwise noted)REV. C(VCC = +3 V to +5 V; REF IN = REF OUT2; TA = TMIN to TMAX unless otherwise noted) AD421 3 REV. CTIMING CHARACTERISTICS1, 2, 3 Parameter(B Versions)UnitsConditions/CommentstCK100n s minData Clock PeriodtCL50ns minData Clock Low TimetCH50ns minData Clock High TimetDW30ns minData Stable WidthtDS30ns minData Setup TimetDH0ns minData Hold TimetLD50ns minLatch Delay TimetLL50ns minLatch Low TimetLH50ns minLatch High TimeNOTES1 Guaranteed by characterization at initial product release, not production Figures 1 and input signals are specified with tr = tf = 5 ns (10% to 90% of VCC)

10 And timed from a voltage level of (VIN + VIL)/2; tr and tf should not exceed 1 s on any subject to change without "N"WORD "N +1"10 1111111100000 01 00 1 CLOCKDATALATCHB15(MSB)B14B13B12B11B10B9B 8B7B6B5B4B3B2B1B0B15B14B13B12(LSB)Figure 1. Serial Interface Waveforms (Normal data Load)CLOCKDATALATCH tCK tCL tCH tDS tDH tDW tLD tLL tLHFigure 2. Serial Interface Timing Diagram(VCC = +3 V to +5 V, TA = TMIN to TMAX unless otherwise noted) AD421 4 REV. CORDERING GUIDET emperaturePackageModelRangeOption*AD421B N 40 C to +85 CN-16AD421BR 40 C to +85 CR-16AD421 BRRL 40 C to +85 CR-16; Reeled SOICEVAL- AD421 EBEvaluation Board*N = Plastic DIP, R = MAXIMUM RATINGS*(TA = +25 C unless otherwise noted)DRIVE, BOOST, COMP to COM.