Si7021-A20 I2C Humidity and Temperature Sensor

1 Rev. 6/22 Copyright 2022 by Silicon LaboratoriesSi7021-A20Si7021-A20I2C Humidity AND Temperature SENSORF eaturesApplicationsDescriptionThe Si7021 I2C Humidity and Temperature Sensor is a monolithic CMOS ICintegrating Humidity and Temperature Sensor elements, an analog-to-digitalconverter, signal processing, calibration data , and an I2C Interface. The patenteduse of industry-standard, low-K polymeric dielectrics for sensing Humidity enablesthe construction of low-power, monolithic CMOS Sensor ICs with low drift andhysteresis, and excellent long term Humidity and Temperature sensors are factory-calibrated and the calibrationdata is stored in the on-chip non-volatile memory.

2 This ensures that the sensorsare fully interchangeable, with no recalibration or software changes Si7021 is available in a 3x3 mm DFN package and is reflow solderable. It canbe used as a hardware- and software-compatible drop-in upgrade for existing RH/ Temperature sensors in 3x3 mm DFN-6 packages, featuring precision sensingover a wider range and lower power consumption. The optional factory-installedcover offers a low profile, convenient means of protecting the Sensor duringassembly ( , reflow soldering) and throughout the life of the product, excludingliquids (hydrophobic/oleophobic) and Si7021 offers an accurate, low-power, factory-calibrated digital solution idealfor measuring Humidity , dew-point, and Temperature , in applications ranging fromHVAC/R and asset tracking to industrial and consumer platforms.

3 Precision Relative Humidity Sensor 3% RH (max), 0 80% RH High Accuracy Temperature Sensor C (max), 10 to 85 C 0 to 100% RH operating range Up to 40 to +125 C operatingrange Wide operating voltage( to V) Low Power Consumption 150 A active current 60 nA standby current Factory-calibrated I2C Interface Integrated on-chip heater 3x3 mm DFN Package Excellent long term stability Optional factory-installed cover Low-profile Protection during reflow Excludes liquids and particulates HVAC/R Thermostats/humidistats Respiratory therapy White goods Indoor weather stations Micro-environments/ data centers Automotive climate control anddefogging Asset and goods tracking Mobile phones and tabletsPatent Protected.

4 Patents pendingOrdering Information:See page AssignmentsDNCSCLVDD1265 GNDSDA34 DNCTop ViewSi7021-A202 Rev. Block DiagramADCGNDH umidity Sensor Control LogicSCLSi7021 Temp RefI2C InterfaceSDAVddCalibration MemorySi7021-A20 Rev. OF CONTENTSS ectionPage1. Electrical Specifications .. 42. Typical Application Circuits .. 113. Bill of Materials .. 124. Functional Description .. Relative Humidity Sensor Accuracy .. Hysteresis .. Prolonged Exposure to High Humidity .. PCB Assembly .. Protecting the Sensor .. Bake/Hydrate Procedure .. Long Term Drift/Aging .. 175. I2C Interface .. Issuing a Measurement Command .. Reading and Writing User Registers .. Electronic Serial Number.

5 Firmware Revision .. Heater .. 256. Control Registers .. Register Descriptions .. 267. Pin Descriptions: Si7021 (Top View) .. 288. Ordering Guide .. 299. Package Outline .. Package Outline: 3x3 6-pin DFN .. Package Outline: 3x3 6-pin DFN with Protective Cover .. 3110. PCB Land Pattern and Solder Mask Design .. 3211. Top Marking .. Si7021 Top Marking .. Top Marking Explanation .. 3312. Additional Reference Resources .. 34 Document Change List ..35Si7021-A204 Rev. Electrical SpecificationsUnless otherwise specified, all min/max specifications apply over the recommended operating 1. Recommended Operating ConditionsParameterSymbolTest ConditionMinTypMaxUnitPower TemperatureTAI and Y grade 40 +125 COperating TemperatureTAG grade 40 +85 CTable 2.

6 General < VDD < V; TA= 40 to 85 C (G grade) or 40 to 125 C (I/Y grade); default conversion time unless otherwise ConditionMinTypMaxUnitInput Voltage HighVIHSCL, SDA VInput Voltage Low VILSCL, SDA pins Voltage RangeVINSCL, SDA pins with respect to VDDVI nput LeakageIILSCL, SDA pins 1 AOutput Voltage LowVOLSDA pin; IOL= ; VDD= V pin; IOL= ; VDD= ConsumptionIDDRH conversion in progress 150180 ATemperature conversion in progress 90120 AStandby, 40 to +85 C2 AStandby, 40 to +125 C2 APeak IDD during powerup3 IDD during I2C operations4 Current5 IHEAT to a RH measurement will also automatically initiate a Temperature measurement. The total conversion time will be tCONV(RH) + tCONV(T).

7 2. No conversion or I2C transaction in progress. Typical values measured at 25 Occurs once during powerup. Duration is <5 Occurs during I2C commands for Reset, Read/Write User Registers, Read EID, and Read Firmware Version. Duration is <100 s when I2C clock speed is >100 kHz (>200 kHz for 2-byte commands).5. Additional current consumption when HTRE bit enabled. See Section Heater for more Rev. Time1tCONV12-bit RH 1012ms11-bit RH RH RH Temperature Temperature Temperature Temperature TimetPUFrom VDD V to ready for a conversion, 25 C 1825msFrom VDD V to ready for a conversion, full Temperature range 80 After issuing a software resetcommand 515 Table 3. I2C Interface VDD V; TA = 40 to +85 C (G grade) or 40 to +125 C (I/Y grade) unless otherwise ConditionMinTypMaxUnitHysteresisVHYSHigh -to-low versus low-to-high x VDD VSCLK Frequency2fSCL 400kHzSCL High sSCL Low sStart Hold sStart Setup values are referenced to VIL and/or Depending on the conversion command, the Si7021 may hold the master during the conversion (clock stretch).

8 At above 100 kHz SCL, the Si7021 may also hold the master briefly for user register and device ID transactions. At the highest I2C speed of 400 kHz the stretching will be <50 Pulses up to and including 50 ns will be 2. General Specifications (Continued) < VDD < V; TA= 40 to 85 C (G grade) or 40 to 125 C (I/Y grade); default conversion time unless otherwise a RH measurement will also automatically initiate a Temperature measurement. The total conversion time will be tCONV(RH) + tCONV(T).2. No conversion or I2C transaction in progress. Typical values measured at 25 Occurs once during powerup. Duration is <5 Occurs during I2C commands for Reset, Read/Write User Registers, Read EID, and Read Firmware Version.

9 Duration is <100 s when I2C clock speed is >100 kHz (>200 kHz for 2-byte commands).5. Additional current consumption when HTRE bit enabled. See Section Heater for more Rev. 1. I2C Interface Timing DiagramStop Setup sBus Free TimetBUFB etween Stop and sSDA Setup TimetDS100 nsSDA Hold TimetDH100 nsSDA Valid TimetVD;DATFrom SCL low to data valid sSDA Acknowledge Valid TimetVD;ACKFrom SCL low to data valid sSuppressed Pulse Width3tSPS50 nsTable 3. I2C Interface Specifications1 (Continued) VDD V; TA = 40 to +85 C (G grade) or 40 to +125 C (I/Y grade) unless otherwise values are referenced to VIL and/or Depending on the conversion command, the Si7021 may hold the master during the conversion (clock stretch).

10 At above 100 kHz SCL, the Si7021 may also hold the master briefly for user register and device ID transactions. At the highest I2C speed of 400 kHz the stretching will be <50 Pulses up to and including 50 ns will be BitStop BittBUFtSTStVD : ACKtSPStSPSi7021-A20 Rev. 4. Humidity VDD V; TA = 30 C; default conversion time unless otherwise ConditionMinTypMaxUnitOperating Range1 Non-condensing0 100%RHAccuracy2, 30 80% RH 2 3%RH80 100% RHSee Figure resolution %RH RMS11-bit resolution 10-bit resolution 8-bit resolution Response Time4 63%1 m/s airflow, with cover 18 S1 m/s airflow, without cover 17 Drift vs. Temperature %RH/ CHysteresis 1 %RHLong Term Stability3 < %RH/ Humidity operating range is 20% to 80% RH (non-condensing) over 10 C to 60 C.