Si 7 0 1 5 - A20 D IGITA L I 2 C H UMIDITY AND TEMPERATURE S ENSOR Features Precision Relative Humidity Sensor 4.5% RH (max), 0-80% RH High-Accuracy Temperature Sensor 1 C (max), -10 to 85 C 0 to 100% RH operating range 0 to +70 C operating range (FM) -40 to +85 C operating range (GM) Low Voltage Operation (1.9 to 3.6 V) Low Power Consumption 150 A active current 60 nA standby current Drop-In Upgrade for Si7005 Factory-calibrated I2C Interface Integrated on-chip heater 4x4 mm QFN package Excellent long term stability Optional factory-installed cover Low-profile during reflow Excludes liquids and particulates Ordering Information Protection See page 31. Patent protected; patents pending Applications DNC DNC DNC DNC DNC GND 23 22 21 20 19 18 DNC 2 17 DNC SCL 3 16 DNC 11 12 DNC 13 DNC GND DNC 10 14 DNC 6 DNC 15 CS 5 9 4 VDD SDA DNC 8 The Si7015 I C Humidity and Temperature Sensor is a monolithic CMOS IC integrating humidity and temperature sensor elements, an analog-todigital converter, signal processing, calibration data, and an I2C Interface. The patented use of industry-standard, low-K polymeric dielectrics for sensing humidity enables the construction of low-power, monolithic CMOS Sensor ICs with low drift and hysteresis and excellent long term stability. 1 DNC 7 2 GND DNC Description 24 Pin Assignments Micro-environments/data centers Industrial controls Weather stations Asset tracking and storage GND HVAC/R Thermostats/humidistats Instrumentation White goods Each unit is factory-calibrated, and the calibration data is stored in the onchip non-volatile memory. This ensures that the sensors are fully interchangeable, with no recalibration or software changes required. The Si7015 can be used as a drop-in upgrade for the Si7005 with only minor software changes because the register sets are the same, and the 4x4 mm QFN package is footprint-compatible with that of the Si7005. The device is compatible with standard SMT assembly processes, such as reflow. The optional factory-installed cover offers a low profile and convenient means of protecting the sensor during assembly (e.g., reflow soldering) and throughout the life of the product, excluding liquids (hydrophobic/oleophobic) and particulates. The Si7015 offers an accurate, low-power, factory-calibrated digital solution ideal for measuring humidity, dew-point, and temperature in applications ranging from HVAC/R and asset tracking to industrial and consumer platforms. Rev. 1.2 8/16 Copyright (c) 2016 by Silicon Laboratories Si7015-A20 Si7015-A20 Functional Block Diagram 2 Rev. 1.2 Si7015-A20 TABLE O F C ONTENTS Section Page 1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2. Typical Application Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 3. Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2. Relative Humidity Sensor Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.3. Temperature Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.4. Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.5. Prolonged Exposure to High Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.6. PCB Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.7. Protecting the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.8. Bake/Hydrate Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.9. Long Term Drift/Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5. Host Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.1. I2C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.2. I2C Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 6. Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 6.1. Register Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 7. Pin Descriptions: Si7015 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 8. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.1. 24-Pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 9.2. 24-Pin QFN with Protective Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 10. PCB Land Pattern and Solder Mask Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 11. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 11.1. Si7015 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 11.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 12. Additional Reference Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 Rev. 1.2 3 Si7015-A20 1. Electrical Specifications Unless otherwise specified, all min/max specifications apply over the recommended operating conditions. Table 1. Recommended Operating Conditions Parameter Symbol Power Supply Test Condition VDD Min Typ Max Unit 1.9 -- 3.6 V Operating Temperature TA F grade 0 -- +70 C Operating Temperature TA G grade -40 -- +85 C Table 2. General Specifications 1.9 < VDD < 3.6 V; TA = -40 to 85 C (G grade) or 0 to 70 C (F grade); default conversion time unless otherwise noted. Parameter Symbol Test Condition1 Min Typ Max Unit Input Voltage High VIH AD0, SCL, SDA pins 0.7xVDD -- -- V Input Voltage Low VIL AD0, SCL, SDA pins -- -- 0.3xVDD V Input Voltage Range VIN SCL, SDA, RSTb pins with respect to GND 0.0 -- VDD V Input Leakage IIL SCL, SDA pins; VIN = GND -- -- 1 A CS pin (200K nominal pull up); Vin = GND Output Voltage Low Current Consumption VOL IDD -- -- 0.6 V SDA pin; IOL = 1.2 mA; VDD = 1.9 V -- -- 0.4 V RH conversion in progress -- 150 180 A Temperature conversion in progress -- 90 120 A CS < VIL; no conversion in progress; VDD = 3.3 V; SDA = SCL VIH; HEAT = 1 -- 24 -- Standby2, -40 to +85C -- 0.06 0.62 A -- 3.5 4.0 mA -- 3.5 4.0 mA RH Normal (Fast = 0) -- 5.8 7.0 ms RH Fast (Fast = 1) -- 2.6 3.1 ms Temperature Normal (Fast = 0) -- 4.0 6.2 ms Temperature Fast (Fast = 1) -- 1.5 2.4 ms Peak IDD during tCONV A SDA pin; IOL = 2.5 mA; VDD = 3.3 V Peak IDD during powerup Conversion Time 5xVDD I2C 3 operations4 mA Notes: 1. Initiating 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 C. 3. Occurs once during powerup. Duration is <5 msec. 4. Occurs during I2C commands for Read Device ID and Read Firmware Version. Duration is < 100 s when I2C clock speed is >100 kHz. 4 Rev. 1.2 Si7015-A20 Table 2. General Specifications (Continued) 1.9 < VDD < 3.6 V; TA = -40 to 85 C (G grade) or 0 to 70 C (F grade); default conversion time unless otherwise noted. Parameter Symbol Test Condition1 Min Typ Max Unit Wake Up Time tCS From CS < VIL to ready for a temp/RH conversion -- -- 1 ms Power Up Time tPU From VDD 1.9 V to ready for a temp/ RH conversion, 25C -- 18 25 ms From VDD 1.9 V to ready for a temp/ RH conversion, full temperature range -- -- 80 ms Notes: 1. Initiating 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 C. 3. Occurs once during powerup. Duration is <5 msec. 4. Occurs during I2C commands for Read Device ID and Read Firmware Version. Duration is < 100 s when I2C clock speed is >100 kHz. Table 3. I2C Interface Specifications1 1.9 VDD 3.6 V; TA = 0 to 70 C (F grade) or -40 to +85 C (G grade) unless otherwise noted. Parameter Symbol Test Condition Min Typ Max Unit Hysteresis VHYS High-to-low versus low-tohigh transition 0.05 x VDD -- -- V SCLK Frequency fSCL -- -- 400 kHz SCL High Time tSKH 0.6 -- -- s SCL Low Time tSKL 1.3 -- -- s Start Hold Time tSTH 0.6 -- -- s Start Setup Time tSTS 0.6 -- -- s Stop Setup Time tSPS 0.6 -- -- s Bus Free Time tBUF 1.3 -- -- s SDA Setup Time tDS 100 -- -- ns SDA Hold Time tDH 100 -- -- ns SDA Valid Time tVD;DAT From SCL low to data valid -- -- 0.9 s SDA Acknowledge Valid Time tVD;ACK From SCL low to data valid -- -- 0.9 s 50 -- -- ns Suppressed Pulse Width2 Between Stop and Start tSP Notes: 1. All values are referenced to VIL and/or VIH. 2. Pulses up to and including 50ns will be suppressed. Rev. 1.2 5 Si7015-A20 tSKH 1/fSCL tSKL tSP SCL tBUF tSTH tDS D6 SDA D5 tDH D4 D0 tSPS R/W ACK Start Bit Stop Bit tVD : ACK tSTS Figure 1. I2C Interface Timing Diagram 6 Rev. 1.2 Si7015-A20 Table 4. Humidity Sensor 1.9 VDD 3.6 V; TA = 30 C; default conversion time unless otherwise noted. Parameter Symbol 1 Operating Range Accuracy2, 3 Test Condition Min Typ Max Unit Non-condensing 0 -- 100 %RH 0 - 80% RH -- 3.0 4.5 %RH 80 - 100% RH Repeatability/Noise See Figure 2. %RH Normal Mode -- 0.05 -- %RH RMS Fast Mode -- 0.2 -- %RH RMS 1 m/s airflow, with cover -- 18 -- 1 m/s airflow, without cover -- 17 -- Drift vs. Temperature -- 0.05 -- %RH/C Hysteresis -- 1 -- %RH Long Term Stability3 -- < 0.25 -- %RH/yr Response Time4 63% S Notes: 1. Recommended humidity operating range is 20% to 80% RH (non-condensing) over -10 C to 60 C. Prolonged operation beyond these ranges may result in a shift of sensor reading with slow recovery time. 2. Excludes hysteresis, long term drift, and certain other factors and is applicable to non-condensing environments only. See Section "4.2. Relative Humidity Sensor Accuracy" for more details. 3. Drift due to aging effects at typical room conditions of 30C and 30% to 50%. May be impacted by dust, vaporized solvents or other contaminants, e.g., out-gassing tapes, adhesives, packaging materials, etc. See Section "4.9. Long Term Drift/Aging". 4. Response time to a step change in RH. Time for the RH output to change by 63% of the total RH change. RHAccuracy Max.RHError(%) Typ.RHError(%) 10 RHMeasurementError(%) 9 8 7 6 5 4 3 2 1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 RelativeHumidity(%) Figure 2. RH Accuracy at 30 C Rev. 1.2 7 Si7015-A20 Table 5. Temperature Sensor 1.9 VDD 3.6 V; TA = -40 to +85 C (G grade) or 0 to +70 C (F grade), default conversion time unless otherwise noted. Parameter Symbol Operating Range Accuracy1 Test Condition Min Typ Max Unit F Grade 0 -- +70 C G Grade -40 -- +85 C 0 C < tA < 70 C -- 0.5 1.0 C -40 C < tA < 85 C Repeatability/Noise Response Time2 63% Figure 3. C Normal Mode -- 0.02 -- C RMS Fast Mode -- 0.08 -- C RMS Unmounted device -- 0.7 -- s Si7015-EB board -- 5.1 -- s -- < 0.01 -- Long Term Stability C/Yr Notes: 1. 14b measurement resolution (default). 2. Time to reach 63% of final value in response to a step change in temperature. Actual response time will vary dependent on system thermal mass and air-flow. Figure 3. Temperature Accuracy* Note: Figure 3 only applies to G-grade devices beyond 70C. 8 Rev. 1.2 Si7015-A20 Table 6. Thermal Characteristics Symbol Test Condition QFN-24 Unit Junction-to-Air Thermal Resistance JA JEDEC 4-layer board 55 C/W Junction-to-Air Thermal Resistance JA 2-layer evaluation PCB with minimal thermal pad 110 C/W Parameter Table 7. Absolute Maximum Ratings1,2 Min Typ Max Unit Ambient Temperature under Bias -55 -- 125 C Storage Temperature -65 -- 150 C Voltage on SDA or SCL Pin with Respect to GND -0.3 -- VDD+ 0.3 V Voltage on CS pin with Respect to GND -0.3 -- VDD + 0.3 V Voltage on VDD with Respect to GND -0.3 -- 4.2 V HBM -- -- 2 kV CDM -- -- 1.25 kV MM -- -- 250 V Parameter Symbol Test Condition ESD Tolerance Notes: 1. Absolute maximum ratings are stress ratings only; operation at or beyond these conditions is not implied and may shorten the life of the device or alter its performance. 2. Special handling considerations apply; see "AN607: Si70xx Humidity Sensor Designer's Guide" for details. Rev. 1.2 9 Si7015-A20 19 GND 20 DNC 21 DNC 22 23 DNC DNC DNC Si7015 SDA CS DNC DNC 17 16 15 14 13 12 11 7 18 DNC DNC GND DNC DNC 6 U3 SCL DNC 5 DNC VDD 4 DNC 10 3 DNC 9 2 GND GND SDA * R2 10K 8 1 R1 10K DNC EPAD VDD SCL * 24 25 2. Typical Application Circuit CSb C1 0.1uF GND Figure 4. Typical Application Circuit* *Note: If Si7015 is replacing an Si7005, the capacitor connected to Pin 10 may be left connected or removed. 10 Rev. 1.2 Si7015-A20 3. Bill of Materials Table 8. Typical Application Circuit BOM* Reference Description Mfr Part Number Manufacturer C1 Capacitor, 0.1 F, 6.3 V, X7R, 0603 C0603X7R6R3-104M Venkel R1* Resistor, 10 k, 5%, 1/16 W, 0603 CR0603-16W-1002J Venkel R2* Resistor, 10 k, 5%, 1/16 W, 0603 CR0603-16W-1002J Venkel U1 IC, digital temperature/humidity sensor Si7015-A20 Silicon Labs *Note: Typical value shown. Optimal value depends on bus capacitance and speed of bus operation; not needed if present elsewhere in the system. Rev. 1.2 11 Si7015-A20 4. Functional Description Figure 5. Si7015 Functional Block Diagram 4.1. Overview The Si7015 is a digital relative humidity and temperature sensor. This monolithic CMOS IC integrates temperature and humidity sensor elements, an analog-to-digital converter, signal processing, calibration data, and an I2C host interface. Both the temperature and humidity sensors on each unit are factory-calibrated and the calibration data is stored in the on-chip non-volatile memory. This ensures that the sensors are fully interchangeable, with no recalibration or software changes required. While the Si7015 is largely a conventional mixed-signal CMOS integrated circuit, relative humidity sensors in general and those based on capacitive sensing using polymeric dielectric have unique application and use requirements that are not common to conventional (non-sensor) ICs. Chief among those are: The need to protect the sensor during board assembly, i.e., solder reflow, and the need to subsequently rehydrate the sensor. The need to apply temperature correction to the humidity readings. The need to protect the sensor from damage or contamination during the product life-cycle. The impact of prolonged exposure to extremes of temperature and/or humidity and their potential effect on sensor accuracy. The effects of humidity sensor "memory". Each of these items is discussed in more detail in the following sections. 12 Rev. 1.2 Si7015-A20 4.2. Relative Humidity Sensor Accuracy To determine the accuracy of a relative humidity sensor, it is placed in a temperature and humidity controlled chamber. The temperature is set to a convenient fixed value (typically 30 C) and the relative humidity is swept from 20 to 80% and back to 20% in the following steps: 20% - 40% - 60% - 80% - 80% - 60% - 40% - 20%. At each set-point, the chamber is allowed to settle for a period of 60 minutes before a reading is taken from the sensor. Prior to the sweep, the device is allowed to stabilize to 50%RH. The solid top and bottom trace in Figure 6, "Measuring Sensor Accuracy Including Hysteresis," shows the result of a typical sweep after non-linearity compensation. RHAccuracyvs.RHSetPoint 5 4 Hysteresis 3 %RHAccuracy 2 1 0 1 10 20 30 40 50 60 70 80 90 2 3 4 5 %RHSetpoint Figure 6. Measuring Sensor Accuracy Including Hysteresis The RH accuracy is defined as the center (dashed) line shown in Figure 6, which is the average of the two data points at each relative humidity set-point. In this case, the sensor shows an accuracy of 0.25%RH. The Si7015 accuracy specification (Table 4) includes the following: Unit-to-unit and lot-to-lot variation in non-linearity compensation of factory calibration Margin for shifts that can occur during solder reflow. The accuracy specification does not include the following: Accuracy Hysteresis (typically 1%) Effects from long term exposure to very humid conditions Contamination of the sensor by particulates, chemicals, etc. Other aging related shifts ("Long-term stability") Variations due to temperature Rev. 1.2 13 Si7015-A20 4.3. Temperature Compensation The Si7015 relative humidity sensor is calibrated at a temperature of 30 C; it is at this temperature that the sensor will give the most accurate relative humidity readings. For relative humidity measurements at other temperatures, the RH reading from the Si7015 must be compensated for the change in temperature relative to 30 C. Temperature-compensated relative humidity readings can be calculated as follows: RH TempCompensated = RH Linear + Temperature - 30 RH Linear Q 1 + Q 0 Where: RHTempCompensated RHLinear is the temperature compensated relative humidity value in %RH. is the linear corrected relative humidity value in %RH. Temperature is the ambient temperature in C as measured by the Si7015 on chip temperature sensor. and Q0 are unit-less correction coefficients derived through characterization of Si7015s by Silicon Laboratories. This temperature compensation is most accurate in the range of 15-50 C. The values for the correction coefficients are shown in Table 9. Q1 Table 9. Linearization Coefficients Coefficient Value Q0 0.060162 Q1 0.000508 4.4. Hysteresis The moisture absorbent film (polymeric dielectric) of the humidity sensor will carry a memory of its exposure history, particularly its recent or extreme exposure history. A sensor exposed to relatively low humidity will carry a negative offset relative to the factory calibration, and a sensor exposed to relatively high humidity will carry a positive offset relative to the factory calibration. This factor causes a hysteresis effect illustrated by the solid top and bottom traces in Figure 6. The hysteresis value is the difference in %RH between the maximum absolute error on the decreasing humidity ramp and the maximum absolute error on the increasing humidity ramp at a single relative humidity Setpoint and is expressed as a bipolar quantity relative to the average, the center dashed trace in Figure 6. In the case of Figure 6, the measurement uncertainty due to the hysteresis effect is 1.05%RH. 4.5. Prolonged Exposure to High Humidity Prolonged exposure to high humidity will result in a gradual upward drift of the RH reading. The shift in sensor reading resulting from this drift will generally disappear slowly under normal ambient conditions. The amount of shift is proportional to the magnitude of relative humidity and the length of exposure. In the case of lengthy exposure to high humidity, some of the resulting shift may persist indefinitely under typical conditions. It is generally possible to substantially reverse this affect by baking the device (see Section "4.8. Bake/Hydrate Procedure"). 14 Rev. 1.2 Si7015-A20 4.6. PCB Assembly 4.6.1. Soldering Like most ICs, Si7015 devices are shipped from the factory vacuum-packed with an enclosed desiccant to avoid any drift during storage and to prevent any moisture-related issues during solder reflow. The following guidelines should be observed during PCB assembly: Si7015 devices are compatible with standard board assembly processes. Devices should be soldered using reflow per the recommended card reflow profile. See Section "10. PCB Land Pattern and Solder Mask Design" for the recommended card reflow profile. A "no clean" solder process is recommended to minimize the need for water or solvent rinses after soldering. Cleaning after soldering is possible, but must be done carefully to avoid impacting the performance of the sensor. See application note, "AN607: Si70xx Humidity Sensor Designer's Guide" for more information on cleaning. It is essential that the exposed polymer sensing film be kept clean and undamaged. This can be accomplished by careful handling and a clean, well-controlled assembly process. When in doubt or for extra protection, a heat-resistant, protective cover such as Kapton(R) KPPD-1/8 can be installed during PCB assembly. Si7015s may be ordered with a factory-fitted, solder-resistant protective cover. This cover provides protection during PCB assembly or rework but without the time and effort required to install and remove the Kapton(R) tape. It can be left in place for the lifetime of the product, preventing liquids, dust, or other contaminants from coming into contact with the polymer sensor film. See Section "8. Ordering Guide" for a list of ordering part numbers that include the cover. 4.6.2. Rehydration The measured humidity value will generally shift slightly after solder reflow. A portion of this shift is permanent and is accounted for in the accuracy specifications in Table 4. After soldering, an Si7015 should be allowed to equilibrate under controlled RH conditions (room temperature, 45-55%RH) for at least 48 hours to eliminate the remainder of the shift and return the device to its specified accuracy performance. Rev. 1.2 15 Si7015-A20 4.6.3. Rework To maintain the specified sensor performance, care must be taken during rework to minimize the exposure of the device to excessive heat and to avoid damage/contamination or a shift in the sensor reading due to liquids, solder flux, etc. Manual touch-up using a soldering iron is permissible under the following guidelines: The exposed polymer sensing film must be kept clean and undamaged. A protective cover is recommended during any rework operation (Kapton(R) tape or the factory-installed cover). Flux must not be allowed to contaminate the sensor; liquid flux is not recommended even with a cover in place. Conventional lead-free solder with rosin core is acceptable for touch-up as long as a cover is in place during the rework. If possible, avoid water or solvent rinses after touch-up. Cleaning after soldering is possible, but must be done carefully to avoid impacting the performance of the sensor. See application note, "AN607: Si70xx Humidity Sensor Designer's Guide" for more information on cleaning. Minimize the heating of the device. Soldering iron temperature should not exceed 350 C and the contact time per pin should not exceed five seconds. Hot air rework is not recommended. If a device must be replaced, remove the device by hot air and solder a new part in its place by reflow following the guidelines above. *Note: All trademarks are the property of their respective owners. Figure 7. Si7015 with Factory-Installed Protective Cover 16 Rev. 1.2 Si7015-A20 4.7. Protecting the Sensor Because the sensor operates on the principal of measuring a change in capacitance, any changes to the dielectric constant of the polymer film will be detected as a change in relative humidity. Therefore, it is important to minimize the probability of contaminants coming into contact with the sensor. Dust and other particles as well as liquids can affect the RH reading. It is recommended that a cover is employed in the end system that blocks contaminants but allows water vapor to pass through. Depending on the needs of the application, this can be as simple as plastic or metallic gauze for basic protection against particulates or something more sophisticated such as a hydrophobic membrane providing up to IP67 compliant protection. The Si7015 may be ordered with a factory-fitted, solder-resistant cover that can be left in place for the lifetime of the product. It is very low-profile, hydrophobic and oleophobic. See Section "8. Ordering Guide" for a list of ordering part numbers that include the cover. A dimensioned drawing of the IC with the cover is included in Section "9. Package Outline". Other characteristics of the cover are listed in Table 10. Table 10. Specifications of Protective Cover Parameter Material Value PTFE Operating Temperature -40 to +125 C Maximum Reflow Temperature IP Rating (per IEC 529) 260 C IP67 4.8. Bake/Hydrate Procedure After exposure to extremes of temperature and/or humidity for prolonged periods, the polymer sensor film can become either very dry or very wet; in each case the result is either high or low relative humidity readings. Under normal operating conditions, the induced error will diminish over time. From a very dry condition, such as after shipment and soldering, the error will diminish over a few days at typical controlled ambient conditions, e.g., 48 hours of 45 %RH 55. However, from a very wet condition, recovery may take significantly longer. To accelerate recovery from a wet condition, a bake and hydrate cycle can be implemented. This operation consists of the following steps: Baking the sensor at 125 C for 12 hours at 30 C in 75 %RH for 10 hours Following this cycle, the sensor will return to normal operation in typical ambient conditions after a few days. Hydration 4.9. Long Term Drift/Aging Over long periods of time, the sensor readings may drift due to aging of the device. Standard accelerated life testing of the Si7015 has resulted in the specifications for long-term drift shown in Table 4 and Table 5. This contribution to the overall sensor accuracy accounts only for the long-term aging of the device in an otherwise benign operating environment and does not include the affects of damage, contamination, or exposure to extreme environmental conditions. Rev. 1.2 17 Si7015-A20 5. Host Interface 5.1. I2C Interface The Si7015 has an I2C serial interface with a 7-bit address of 0x40. The Si7015 is a slave device supporting data transfer rates up to 400 kHz. Table 20 shows the register summary of the Si7015. 5.1.1. Performing a Relative Humidity Measurement The following steps should be performed in sequence to take a relative humidity measurement: 1. Set START (D0) in CONFIG to begin a new conversion. 2. Poll RDY (D0) in STATUS (register 0) until it is low (= 0). (This must be done at least once prior to reading results even if the host waits longer than tCONV.) 3. Read the upper and lower bytes of the RH value from DATAh and DATAl (registers 0x01 and 0x02), respectively. Table 11 shows the format of the 12-bit relative humidity result. 4. Convert the RH value to %RH using the following equation: RH %RH = --------- - 24 16 where RH is the measured value returned in DATAh:DATAI. 5. Apply temperature compensation as discussed elsewhere in this data sheet. Due to normal variations in RH accuracy of the device as described in Table 4, it is possible for the measured value of %RH to be slightly less than 0 when the actual RH level is close to or equal to 0. Similarly, the measured value of %RH may be slightly greater than 100 when the actual RH level is close to or equal to 100. This is expected behavior, and it is acceptable to limit the range of RH results to 0 to 100%RH in the host software by truncating values that are slightly outside of this range. Table 12 shows the 12-bit values that correspond to various measured RH levels. Table 11. 12-Bit Relative Humidity Result Available in Registers 1 and 2 DATAh D7 D6 D5 D4 D3 DATAI D2 D1 D0 D7 12-Bit Relative Humidity Code 18 Rev. 1.2 D6 D5 D4 D3 D2 D1 D0 Si7015-A20 Table 12. Typical %RH Measurement Codes for 0 to 100% RH Range %RH 12 Bit Code Dec Hex 0 384 180 10 544 220 20 704 2C0 30 864 360 40 1024 400 50 1184 4A0 60 1344 540 70 1504 5E0 80 1664 680 90 1824 720 100 1984 7C0 The above sequence assumes normal mode, i.e., tCONV = 5.8 ms (typical). Conversions may be performed in fast mode. See Section "5.1.4. Fast Conversion Mode". Rev. 1.2 19 Si7015-A20 5.1.2. Performing a Temperature Measurement The following steps should be performed in sequence to take a temperature measurement: 1. Set START (D0) and TEMP (D4) in CONFIG (register 0x03) to begin a new conversion, i.e., write CONFIG with 0x11 2. Poll RDY (D0) in STATUS (register 0) until it is low (=0). This must be done at least once prior to reading results even if the host waits longer than tCONV. 3. Read the upper and lower bytes of the temperature value from DATAh and DATAl (registers 0x01 and 0x02), respectively Table 13 shows the format of the 14-bit temperature result. This value may be converted to C using the following equation: TEMP Temperature C = ----------------- - 50 32 where TEMP is the measured value returned in DATAh:DATAI. Table 14 shows the 14-bit values that correspond to various measured temperature levels. Table 13. 14-Bit Temperature Result Available in Registers 1 and 2 DATAh D7 D6 D5 D4 D3 DATAI D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 14-Bit Temperature Code The above sequence assumes normal mode, i.e., tCONV = 5.8 ms (typical). Conversions may be performed in fast mode. See Section "5.1.4. Fast Conversion Mode". 5.1.3. Entering Low-Power Mode Either of the following sequences can be used to place the Si7015 into its low-power standby mode following an RH conversion: Option A: Bring CSb high. This puts the Si7015 in low-power mode and disables I2C communication. This is similar to Si7005 except that the response to CSb high takes only a few usec and the VDD current is <1 A (as opposed to Si7005 which can take >1second and can have VDD current of up to 100 A). Option B: 1. Poll /RDY until it returns zero, indicating that the conversion is finished. 2. Read the results of the RH conversion from DATAh:DATAl. 3. Clear the start bit (START) by writing 0x0 to register 3. 4. Clear the start bit (START) a second time by again writing 0x0 to register 3. The Si7015 does enter its low-power standby mode following a temperature conversion. No action is required in this case. However, please note that doing a temperature conversion following an RH conversion will not put the Si7015 in low power state. 20 Rev. 1.2 Si7015-A20 Table 14. Typical Temperature Measurement Codes for the -40 C to 100 C Range Temp(C) 14 Bit Code Dec Hex -40 320 0140 -30 640 0280 -20 960 03C0 -10 1280 0500 0 1600 0640 10 1920 0780 20 2240 08C0 30 2560 0A00 40 2880 0B40 50 3200 0C80 60 3520 0DC0 70 3840 0F00 80 4160 1040 90 4480 1180 100 4800 12C0 Rev. 1.2 21 Si7015-A20 5.1.4. Fast Conversion Mode The time needed to perform a temperature or RH measurement can be reduced from 5.8 ms (typical) to 2.6 ms (typical) by setting FAST (D5) in CONFIG (register 0x03). Fast mode reduces the total power consumed during a conversion or the average power consumed by the Si7015 when making periodic conversions. It also reduces the resolution of the measurements. 5.1.5. Heater The Si7015 relative humidity sensor contains an integrated, resistive heating element that may be used to raise the temperature of the humidity sensor. This element can be used to drive off condensation or to implement dew-point measurement when the Si7015 is used in conjunction with a separate temperature sensor such as another Si7015. The heater can be activated by setting HEAT (D1) in CONFIG (register 0x03). Turning on the heater will reduce the tendency of the humidity sensor to accumulate an offset due to "memory" of sustained high humidity conditions. When the heater is enabled, the reading of the on-chip temperature sensor will be affected (increased). 5.1.6. Device Identification The Si7015 device and its revision level can be determined by reading ID (register 0x11). Table 15 lists the values for the various device revisions and may include revisions not yet in existence. Table 15. Device ID Revision Values Device ID Value 22 D[7:4] D[3:0] 1111 0000 Rev. 1.2 Device Type Revision Level Si7015 A Si7015-A20 5.2. I2C Operation The format of the address byte is shown in Table 16. Table 16. I2C Slave Address Byte A6 A5 A4 A3 A2 A1 A0 R/W 1 0 0 0 0 0 0 1/0 5.2.1. I2C Write Operation To write to a register on the Si7015, the master should issue a start command (S) followed by the slave address, 0x40. The slave address is followed by a 0 to indicate that the operation is a write. Upon recognizing its slave address, the Si7015 issues an acknowledge (A) by pulling the SDA line low for the high duration of the ninth SCL cycle. The next byte the master places on the bus is the register address pointer, selecting the register on the Si7015 to which the data should be transferred. After the Si7015 acknowledges this byte, the master places a data byte on the bus. This byte will be written to the register selected by the address pointer. The Si7015 will acknowledge the data byte, after which the master issues a Stop command (P). See Table 17. Master Slave Table 17. I2C Write Sequence Sequence to Write to a Register S Slave Address W A Address Pointer A Register Data A P A P A P Sequence to Start a Relative Humidity Conversion S 0x40 0 A 0x03 A 0x01 Sequence to Start a Temperature Conversion S 0x40 0 A 0x03 Rev. 1.2 A 0x11 23 Si7015-A20 5.2.2. I2C Read Operation To read a register on the Si7015, the master must first set the address pointer to indicate the register from which the data is to be transferred. Therefore, the first communication with the Si7015 is a write operation. The master should issue a start command (S) followed by the slave address, 0x40. The slave address is followed by a 0 to indicate that the operation is a write. Upon recognizing its slave address, the Si7015 will issue an acknowledge (A) by pulling the SDA line low for the high duration of the ninth SCL cycle. The next byte the master places on the bus is the register address pointer selecting the register on the Si7015 from which the data should be transferred. After the Si7015 acknowledges this byte, the master issues a repeated start command (Sr) indicating that a new transfer is to take place. The Si7015 is addressed once again with the R/W bit set to 1, indicating a read operation. The Si7015 will acknowledge its slave address and output data from the previously-selected register onto the data bus under the control of the SCL signal, the master should not acknowledge (A) the data byte and issue a stop (P) command (see Table 22). However, if a RH or Temperature conversion result (two bytes) is to be read, the master should acknowledge (A) the first data byte and continue to activate the SCL signal. The Si7015 will automatically output the second data byte. Upon receiving the second byte, the master should issue a not Acknowledge (A) followed by a stop command. (See Table 23.) Table 18. I2C Read Sequence for a Single Register Sequence to Read from a Single Register S Slave Address W A Address Pointer A Sr Slave Address R A Register Data A P 1 A ID A P 1 A A P Sequence to Read Device ID S 0x40 0 A 0x11 A Sr 0x40 Sequence to Read RDY bit S 0x40 0 A A 0x00 Sr 0x40 -- RDY Table 19. I2C Read Sequence for RH or Temperature Conversion Result Sequence to Read Conversion Result S Slave Address W A Address Pointer A Sr Slave Address R A Register 1 Data A Register 2 Data A P S 0x40 0 A 0x01 A Sr 0x40 1 A Data H A Data L A P 24 Rev. 1.2 Si7015-A20 5.2.3. Firmware Revision The internal firmware revision can be read with the following I2C transaction: S R Slave Address A FWREV A W A 0x84 NA A 0xB8 A S Slave Address P The values in this field are encoded as follows: 0xFF = Firmware revision 1.0 0x20 = Firmware revision 2.0 Rev. 1.2 25 Si7015-A20 6. Control Registers Table 20 contains a summary of the Si7015 register set. Each register is described in more detail below. Table 20. Si7015 Register Summary Register Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 RSVD RSVD RSVD /RDY I2C Register Summary 0x00 STATUS RSVD RSVD RSVD RSVD 0x01 DATAh Relative Humidity or Temperature, High Byte 0x02 DATAl Relative Humidity or Temperature, Low Byte 0x03 CONFIG RSVD RSVD FAST TEMP RSVD RSVD HEAT START 0x11 ID ID3 ID2 ID1 ID0 0 0 0 0 0x84 0xB8 FWREV MAJREV MINREV Notes: 1. Any register address not listed here is reserved and must not be written. 2. Reserved register bits (RSVD) must always be written as zero; the result of a read operation on these bits is undefined. 6.1. Register Detail Register 0. STATUS Bit D7 D6 D5 D4 D3 D2 D0 Name /RDY Type R Reset Settings = 0000_0001 Bit 7:1 0 26 D1 Name Function Reserved Reserved. Reads undefined. /RDY Ready. 0 = conversion complete; results available in DATAh:DATAl. 1 = conversion in progress. Rev. 1.2 Si7015-A20 Register 0x01. DATAh Bit D7 D6 D5 D4 D3 D2 Name Relative Humidity or Temperature, High Byte Type R D1 D0 Reset Settings = 0000_0000 Bit Name 7:0 DATAh Function Data, High Byte. Eight most significant bits of a temperature or humidity measurement. See Table 11 or Table 13 for the measurement format. Register 0x02. DATAI Bit D7 D6 D5 D4 D3 D2 Name Relative Humidity or Temperature, Low Byte Type Read D1 D0 Reset Settings = 0000_0000 Bit Name 7:0 DATAl Function Data, Low Byte. Eight least significant bits of a temperature or humidity measurement. See Table 11 or Table 13 for the measurement format. Rev. 1.2 27 Si7015-A20 Register 0x03. CONFIG Bit D7 D6 D5 D4 Name FAST Type R/W D3 D2 D1 D0 TEMP HEAT START R/W R/W R/W Reset Settings = 0000_0000 Bit 7:6 Name Function Reserved Reserved. Reads undefined. Always write as zero. 5 FAST Fast Mode Enable. 0 = 5.8 ms (typical) 1 = 2.6 ms (typical) 4 TEMP Temperature Enable. 0 = Relative humidity 1 = Temperature 3:2 Reserved Reserved. Reads undefined. Always write as zero. 1 HEAT Heater Enable. 0 = heater off 1 = heater on 0 START Conversion Start. 0 = do not start a conversion 1 = start a conversion Register 0x11. ID Bit D7 D6 D5 D4 D3 D2 D1 D0 Name ID7 ID6 ID5 ID4 ID3 ID2 ID1 ID0 Type R R R R R R R R Reset Settings = 0101_0000 28 Bit Name 7:0 ID Function Identification. See Section "5.1.6. Device Identification" for reset settings. Rev. 1.2 Si7015-A20 Register 0x84 0xB8. FWREV Bit D7 D6 D5 D4 D3 D2 D1 Name MAJREV MINREV Type R R Bit Name 7:4 MAJREV Major firmware revision number 3:0 MINREV Minor firmware revision number D0 Function Rev. 1.2 29 Si7015-A20 DNC DNC DNC DNC DNC GND 24 23 22 21 20 19 7. Pin Descriptions: Si7015 DNC 5 14 DNC DNC 6 13 DNC 12 15 CS DNC 4 11 SDA GND 16 DNC 10 3 DNC SCL 9 17 DNC VDD 2 8 DNC GND 18 DNC 7 1 DNC GND Table 21. Pin Descriptions Pin # Pin Name Pin Type* 1, 8, 11, 19 GND G 2, 5-7, 12-14, 16-18, 20-24 DNC 3 SCL Description Ground. Do Not Connect. Do not connect any of these pins to supply, ground or any other signal. Internal pull-ups or pull-downs will prevent any of these pins from floating. I I2C Clock Signal. This pin is voltage-tolerant. See Table 2. 4 SDA I/O I2C Data Signal. This pin is voltage-tolerant. See Table 2. 9 VDD S VDD Power Supply (1.9 V < VDD < 3.6 V). 10 DNC I If Si7015 is replacing an Si7005, the capacitor connected to Pin 10 may be left connected or removed. 15 CS I Chip Select--Active Low Signal. Epad TGND G Thermal Paddle. This pad is connected to GND internally. The pad can be connected to GND externally or it can be left open-circuit and used as a thermal input to the on-chip temperature sensor. *Note: G = Ground, S = Power Supply, I = Digital Input, O = Digital Output, I/O = Input/Output. 30 Rev. 1.2 Si7015-A20 8. Ordering Guide Table 22. Si7015 Device Ordering Guide Max Accuracy P/N Description Temp RH Pkg Operating Range (C) Protective Cover Packing Format Si7015-A20-FM Digital temperature/ humidity sensor 1 C 4.5% QFN-24 0 to 70 C N Cut Tape Si7015-A20-FMR Digital temperature/ humidity sensor 1 C 4.5% QFN-24 0 to 70 C N Tape-and-reel Si7015-A20-FM1 Digital temperature/ humidity sensor 1 C 4.5% QFN-24 0 to 70 C Y Cut tape Si7015-A20-FM1R Digital temperature/ humidity sensor 1 C 4.5% QFN-24 0 to 70 C Y Tape-and-reel Si7015-A20-GM Digital temperature/ humidity sensor 1 C 4.5% QFN-24 -40 to +85 C N Cut Tape Si7015-A20-GMR Digital temperature/ humidity sensor 1 C 4.5% QFN-24 -40 to +85 C N Tape-and-reel Si7015-A20-GM1 Digital temperature/ humidity sensor 1 C 4.5% QFN-24 -40 to +85 C Y Cut tape Si7015-A20-GM1R Digital temperature/ humidity sensor 1 C 4.5% QFN-24 -40 to +85 C Y Tape-and-reel Note: The "A" denotes product revision A and "20" denotes firmware version 2.0. Rev. 1.2 31 Si7015-A20 9. Package Outline 9.1. 24-Pin QFN Figure 8 illustrates the package details for the Si7015. Tables 23 and 24 list the values for the dimensions shown in the illustration. There are two package variants with slightly different height dimensions. The two package variants are otherwise interchangeable. Figure 8. 24-Pin Quad Flat No Lead (QFN) Table 23. 24-Pin Package Diagram Dimensions Dimension Min Nom Max Dimension Min Nom Max A1 0.00 0.02 0.05 H1 1.03 1.08 1.13 b 0.18 0.25 0.30 H2 D D2 4.00 BSC. 2.55 e 2.75 0.50 BSC. E E2 2.65 4.00 BSC. 2.55 2.65 2.75 1.68 REF L 0.30 0.35 0.40 aaa -- -- 0.15 bbb -- -- 0.15 ccc -- -- 0.08 ddd -- -- 0.10 Notes: 1. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 2. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. Table 24. Package Variants Variant A Variant B Dimension Min Nom Max Min Nom Max A 0.80 0.90 1.00 0.70 0.75 0.80 Note: All Dimensions are in mm unless otherwise noted. 32 Rev. 1.2 Si7015-A20 9.2. 24-Pin QFN with Protective Cover Figure 9 illustrates the package details for the Si7015 with the optional protective cover. Tables 25 and 26 list the values for the dimensions shown in the illustration. There are two package variants with slightly different height dimensions. The two package variants are otherwise interchangeable. Figure 9. 24-Pin Quad Flat No Lead (QFN) With Protective Cover Table 25. 24-Pin Package Diagram Dimensions Dimension Min Nom Max Dimension Min Nom Max A1 0.00 0.02 0.05 h 0.76 0.83 0.90 b 0.18 025 0.30 L 0.30 0.35 0.40 R1 0.45 0.50 0.55 2.75 aaa -- -- 0.15 D D2 4.00 BSC. 2.55 2.65 e 0.50 BSC. bbb -- -- 0.15 E 4.00 BSC. ccc -- -- 0.08 ddd -- -- 0.10 E2 2.55 2.65 2.75 F1 3.60 3.75 3.90 F2 3.60 3.75 3.90 Notes: 1. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 2. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. Table 26. Package Variants Variant A Variant B Dimension Min Nom Max Min Nom Max A -- 1.27 1.41 -- 1.07 1.21 A2 0.80 0.90 1.00 0.70 0.75 0.80 Note: All Dimensions are in mm unless otherwise noted. Rev. 1.2 33 Si7015-A20 10. PCB Land Pattern and Solder Mask Design Figure 10 illustrates the recommended PCB land pattern for use with the Si7015's 4x4 mm QFN package. Figure 10. Typical QFN-24 PCB Land Pattern 34 Rev. 1.2 Si7015-A20 Table 27. PCB Land Pattern Dimensions Symbol mm C1 4.00 C2 4.00 E 0.50 P1 2.75 P2 2.75 X1 0.30 Y1 0.75 Notes: General 1. All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition (LMC) is calculated based on a Fabrication Allowance of 0.05 mm. 2. This Land Pattern Design is based on the IPC-7351 guidelines. Solder Mask Design 3. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60 m minimum, all the way around the pad. Stencil Design 4. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 5. The stencil thickness should be 0.125 mm (5 mils). 6. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pins. 7. A 2x2 array of 0.95 mm square openings on 1.35 mm pitch should be used for the center ground pad. Card Assembly 8. A No-Clean, Type-3 solder paste is recommended. 9. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. Rev. 1.2 35 Si7015-A20 11. Top Marking 11.1. Si7015 Top Marking 11.2. Top Marking Explanation Mark Method: Laser Pin 1 Indicator: Circle = 0.3 mm Diameter Upper-Left Corner Font Size: 0.40 mm Line 1 Marking: TTTT = Manufacturing Code Note: The top mark may not be visible if the optional protective cover is installed. If needed, the device can be identified by reading the identification register as explained in Section "5.1.6. Device Identification". 36 Rev. 1.2 Si7015-A20 12. Additional Reference Resources AN607: Si70xx Humidity Sensor Designer's Guide AN764: Upgrading from the Si7005 to the Si7015 Rev. 1.2 37 Si7015-A20 DOCUMENT CHANGE LIST Revision 0.9 to Revision 1.0 Updated document revision to 1.0. Revision 1.0 to Revision 1.1 Minor modification to description and dimensions of protective cover due to the addition of a second cover supplier. Revision 1.1 to Revision 1.2 Changed packing format from tube to cut tape for all non-tape & reel part numbers without protective filter covers. 38 Rev. 1.2 Smart. Connected. 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