18-Bit ADC with I2C Interface and Onboard Reference

1 2009 Microchip Technology 1 MCP3421 Features 18-Bit ADC in a SOT-23-6 package Differential Input Operation Self Calibration of Internal Offset and Gain Per Each Conversion On-Board Voltage Reference :- Accuracy: Drift: 15 ppm/ C On-Board Programmable Gain Amplifier (PGA):- Gains of 1,2, 4 or 8 On-Board Oscillator INL: 10 ppm of FSR (FSR = ) Programmable Data Rate Options:- SPS (18 bits)- 15 SPS (16 bits)- 60 SPS (14 bits)- 240 SPS (12 bits) One-Shot or Continuous Conversion Options Low Current Consumption: - 145 A typical (VDD= 3V, Continuous Conversion)- 39 A typical(VDD= 3V, One-Shot Conversion with 1 SPS) Supports I2C Serial Interface :- Standard, Fast and High Speed Modes Single Supply Operation: to Extended Temperature Range: -40 C to +125 CTypical Applications Portable Instrumentation Weigh Scales and Fuel Gauges Temperature sensing with RTD, Thermistor, and Thermocouple Bridge sensing for Pressure, Strain, and TypesDescriptionThe MCP3421 is a single channel low-noise, highaccuracy A/D converter with differential inputs andup to 18 bits of resolution in a small SOT-23-6 on-board precision Reference voltageenables an input range of differentially( voltage = ).

2 The device uses a two-wire I2 Ccompatible serial Interface and operates from a to power MCP3421 device performs conversion at rates , 15, 60, or 240 samples per second (SPS)depending on the user controllable configuration bitsettings using the two-wire I2C serial Interface . Thisdevice has an on-board programmable gain amplifier(PGA). The user can select the PGA gain of x1, x2, x4,or x8 before the analog-to-digital conversion takesplace. This allows the MCP3421 device to convert asmaller input signal with high resolution. The devicehas two conversion modes: (a) Continuous mode and(b) One-Shot mode. In One-Shot mode, the deviceenters a low current standby mode automatically afterone conversion. This reduces current consumptiongreatly during idle MCP3421 device can be used for various highaccuracy analog-to-digital data conversion applicationswhere design simplicity, low power, and small footprintare major Diagram123456 VIN+ VSSSCLVIN-VDDSDAMCP3421 SOT-23-6 VSSVDDVIN+VIN-SCLSDAV oltage ReferenceClock( )I2C InterfaceGain = 1, 2, 4, or 8 VREF ADCC onverterPGAO scillator18-Bit Analog-to-Digital Converter with I2C Interface and On-Board ReferenceMCP3421DS22003E-page 2 2009 Microchip Technology : 2009 Microchip Technology Maximum Ratings inputs and outputs VSS.

3 To VDD+ Input Voltage .. |VDD - VSS|Output Short Circuit Current .. ContinuousCurrent at Input Pins .. 2 mACurrent at Output and Supply Pins .. 10 mAStorage Temperature ..-65 C to +150 CAmbient Temp. with power applied ..-55 C to +125 CESD protection on all pins .. 6kVHBM, 400V MMMaximum Junction Temperature (TJ) ..+150 C Notice: Stresses above those listed under Maximum Rat-ings may cause permanent damage to the device. This is astress rating only and functional operation of the device atthose or any other conditions above those indicated in theoperational listings of this specification is not to maximum rating conditions for extended periodsmay affect device SpecificationsELECTRICAL CHARACTERISTICSE lectrical Specifications: Unless otherwise specified, all parameters apply for TA = -40 C to +85 C, VDD = + , VSS = 0V,VIN+ = VIN- = VREF/2.

4 All ppm units use 2*VREF as full scale Min Typ MaxUnits ConditionsAnalog Inputs Differential Input Range VVIN = VIN+ - VIN-Common-Mode Voltage Range (absolute) (Note 1) VDD+ Input Impedance (Note 2)ZIND (f) M During normal mode operationCommon Mode input ImpedanceZINC (f) 25 M PGA = 1, 2, 4, 8 System PerformanceResolution and No Missing Codes (Note 8)12 BitsDR = 240 SPS14 BitsDR = 60 SPS16 BitsDR = 15 SPS18 BitsDR = SPSData Rate (Note 3)DR176240328 SPSS1,S0 = 00 , (12 bits mode)446082 SPSS1,S0 = 01 , (14 bits mode) ,S0 = 10 , (16 bits mode) ,S0 = 11 , (18 bits mode)Output Noise VRMSTA = +25 C, DR = SPS, PGA = 1, VIN = 0 Integral Nonlinearity (Note 4)INL 1035ppm ofFSRDR = SPS(Note 6)Internal Reference VoltageVREF VNote 1:Any input voltage below or greater than this voltage causes leakage current through the ESD diodes at the input parameter is ensured by characterization and not 100% :This input impedance is due to pF internal input sampling capacitor.

5 3:The total conversion speed includes auto-calibration of offset and :INL is the difference between the endpoints line and the measured code at the center of the quantization :Includes all errors from on-board PGA and :Full Scale Range (FSR) = 2 x = :This parameter is ensured by characterization and not 100% :This parameter is ensured by design and not 100% 4 2009 Microchip Technology Error (Note 5) = 1, DR = SPSPGA Gain Error Match (Note 5) %Between any 2 PGA gainsGain Error Drift (Note 5) 15 ppm/ CPGA=1, DR= SPSO ffset ErrorVOS 1540 VTested at PGA = 1 VDD = and DR = SPSO ffset Drift vs. Temperature 50 nV/ CVDD = Rejection 105 dBat DC and PGA =1, 110 dBat DC and PGA =8,TA = +25 CGain vs. VDD 5 ppm/VTA = +25 C, VDD = to ,PGA = 1 Power Supply Rejection at DC 100 dBTA = +25 C, VDD = to ,PGA = 1 Power RequirementsVoltage Current during ConversionIDDA 155190 AVDD = 145 AVDD = Current during Standby ModeIDDS AI2C Digital Inputs and Digital OutputsHigh level input VDD VDDVLow level input voltageVIL level output voltageVOL VIOL = 3 mA, VDD = + of Schmitt Trigger for inputs (Note 7) VfSCL = 100 kHzSupply Current when I2C bus line is activeIDDB 10 AInput Leakage CurrentIILH 1 AVIH = AVIL = GNDPin Capacitance and I2C Bus CapacitancePin capacitance CPIN 10pFI2C Bus CapacitanceCb 400pFELECTRICAL CHARACTERISTICS (CONTINUED)Electrical Specifications.

6 Unless otherwise specified, all parameters apply for TA = -40 C to +85 C, VDD = + , VSS = 0V,VIN+ = VIN- = VREF/2. All ppm units use 2*VREF as full scale Min Typ MaxUnits ConditionsNote 1:Any input voltage below or greater than this voltage causes leakage current through the ESD diodes at the input parameter is ensured by characterization and not 100% :This input impedance is due to pF internal input sampling capacitor. 3:The total conversion speed includes auto-calibration of offset and :INL is the difference between the endpoints line and the measured code at the center of the quantization :Includes all errors from on-board PGA and :Full Scale Range (FSR) = 2 x = :This parameter is ensured by characterization and not 100% :This parameter is ensured by design and not 100% tested.

7 2009 Microchip Technology 5 MCP3421 TEMPERATURE SPECIFICATIONSE lectrical Characteristics: Unless otherwise indicated, TA = -40 C to +85 C, VDD = + , VSS = RangesSpecified Temperature RangeTA-40 +85 COperating Temperature RangeTA-40 +125 CStorage Temperature RangeTA-65 +150 CThermal Package ResistancesThermal Resistance, 6L SOT-23 JA C/WMCP3421DS22003E-page 6 2009 Microchip Technology : 2009 Microchip Technology PERFORMANCE CURVESNote: Unless otherwise indicated, TA = -40 C to +85 C, VDD = + , VSS = 0V, VIN+ = VIN- = 2-1:INL vs. Supply Voltage (VDD).FIGURE 2-2:INL vs. 2-3:Offset Error vs. 2-4:Output Noise vs. Input 2-5:Total Error vs. Input 2-6:Gain Error vs. :The graphs and tables provided following this note are a statistical summary based on a limited number ofsamples and are provided for informational purposes only.

8 The performance characteristics listed hereinare not tested or guaranteed. In some graphs or tables, the data presented may be outside the specifiedoperating range ( , outside specified power supply range) and therefore outside the warranted (V)PGA = 1 PGA = 2 PGA = 8 PGA = 4 Integral Nonlinearity (% of FSR) -40 -20 020 40 60 80 100 120 140 Temperature (oC)Integral Nonlinearity (% of FSR) VDD = 5 VVDD = = 1-20-15-10-505101520-60 -40 -20020406080 100 120 140 Temperature ( C)Offset Error ( V)VDD = 5 VPGA = 1 PGA = 2 PGA = 8 PGA = -75-50-250255075100 Input Voltage (% of Full Scale)Noise ( V, rms)PGA = 1 PGA = 2 PGA = 8 PGA = 4TA = +25 CVDD = -75-50-250255075100 Input Voltage (% of Full Scale)Total Error (mV)PGA = 1 PGA = 2 PGA = 8 PGA = -40 -20020406080 100 120 140 Temperature ( C)Gain Error (% of FSR)

9 VDD = = 1 PGA = 2 PGA = 8 PGA = 4 MCP3421DS22003E-page 8 2009 Microchip Technology : Unless otherwise indicated, TA = -40 C to +85 C, VDD = + , VSS = 0V, VIN+ = VIN- = 2-7:IDDA vs. 2-8:IDDS vs. 2-9:IDDB vs. 2-10:OSC Drift vs. 2-11:Frequency -40 -20020 40 60 80 100 120 140 Temperature (oC)IDDA ( A)VDD = 5 VVDD = -40 -20 020 40 60 80 100 120 140 Temperature (oC)IDDS (nA)VDD = = 5V0123456789-60 -40 -20020 40 60 80 100 120 140 Temperature (oC)IDDB ( A) VDD = 5 VVDD = = = -40 -20020406080 100 120 140 Temperature ( C)Oscillator Drift (%)VDD = = Rate = Signal Frequency (Hz)Magnitude (dB) 2009 Microchip Technology DESCRIPTIONSThe descriptions of the pins are listed in Table 3-1:PIN FUNCTION TABLE Analog Inputs (VIN+, VIN-)VIN+ and VIN- are differential signal input pins.

10 TheMCP3421 device accepts a fully differential analoginput signal which is connected on the VIN+ and VIN-input pins. The differential voltage that is converted isdefined by VIN = (VIN+ - VIN-) where VIN+ is the voltageapplied at the VIN+ pin and VIN- is the voltage appliedat the VIN- pin. The user can also connect VIN- pin toVSS for a single-ended operation. See Figure 6-4 fordifferential and single-ended connection examples. The input signal level is amplified by the programmablegain amplifier (PGA) before the conversion. Thedifferential input voltage should not exceed an absoluteof (VREF/PGA) for accurate measurement, where VREFis the internal Reference voltage ( ) and PGA isthe PGA gain setting. The converter output code willsaturate if the input range exceeds (VREF/PGA).