Si 7 0 3 4 - A10 D IGITA L I 2 C H UMIDITY AND TEMPERATURE S ENSOR Features Precision Relative Humidity Sensor ± 4% RH (max), 0–80% RH High Accuracy Temperature Sensor ±0.4 °C (max), –10 to 85 °C 0 to 100% RH operating range –40 to +125 °C operating range Low Voltage Operation Low Power Consumption 50 nA, standby current Factory-calibrated I2C Interface Integrated on-chip heater 2x2 mm QFN package Excellent long term stability Applications Mobile smartphones and tablets Consumer electronics HVAC/R Respiratory therapy White goods Ordering Information: See page 23. Asset and goods tracking Thermostats/humidistats Micro-environments/data centers Indoor weather stations Pin Assignments Description DNC The Si7034 I2C Humidity and Temperature Sensor is a monolithic CMOS IC integrating humidity and temperature sensor elements, an analog-to-digital 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. The humidity and temperature sensors 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 calibration or software changes required. The Si7034 is available in a 2x2 mm DFN package and is reflow solderable. It can be used as a hardware- and software-compatible drop-in upgrade for existing RH/ temperature sensors in 2x2 mm QFN-6 packages. The Si7034 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. 1.0 8/15 Copyright © 2015 by Silicon Laboratories VDD 1 SCL 2 6 3 5 GND 4 SDA DNC Top View Patent Protected. Patents pending Si7034-A10 Si7034-A10 Functional Block Diagram Vdd Si7034 Humidity Sensor 1.25V Ref Calibration Memory Control Logic ADC Temp Sensor I2C Interface SDA SCL GND 2 Rev. 1.0 Si7034-A10 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. Relative Humidity Sensor Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2. Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.3. Prolonged Exposure to High Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 4.4. PCB Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.5. Protecting the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.6. Bake/Hydrate Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.7. Long Term Drift/Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5. I2C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1. Issuing a Measurement Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.2. Reading and Writing User Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.3. Measuring Relative Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.4. Measuring Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.5. Firmware Revision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.6. Electronic Serial Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 5.7. Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6. Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 7. Pin Descriptions: Si7034 (Top View) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 8. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 9. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 9.1. Package Outline: 2x2 6-pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 10. PCB Land Pattern and Solder Mask Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 11. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 11.1. Si7034 Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 11.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 12. Additional Reference Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 Rev. 1.0 3 Si7034-A10 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 Operating Temperature Test Condition Min Typ Max Unit VDD 1.67 — 1.98 V TA –40 — +125 °C Table 2. General Specifications 1.67 VDD 1.98 V; TA = –40 to +125 °C unless otherwise noted. Parameter Symbol Test Condition Min Typ Max Unit Input Voltage High VIH SCL, SDA pins 0.7xVDD — — V Input Voltage Low VIL SCL, SDA pins — — 0.3xVDD V Input Voltage Range VIN SCL, SDA pins with respect to GND 0.0 — VDD+2 V Input Leakage IIL SCL, SDA pins — — 1 μA Output Voltage Low VOL SDA pin; IOL = 1.5 mA — — 0.4 V Current Consumption IDD Normal Mode, Temperature conversion in progress1 — 245 288 μA Normal Mode, RH conversion in progress1 — 106 145 μA Fast Mode, parallel temperature and RH conversion in progress2 — 337 398 μA Fast Mode, RH conversion in progress3 — 106 145 μA °C5 — 0.05 0.56 μA Standby, –40 to +125 °C5 — 0.05 5.2 μA — 4 5.1 mA — 3.5 4 mA — 11.6 17 µA — 6.4 to 53.5 — mA Standby, –40 to +85 Peak IDD during powerup6 Peak IDD during I2C operations7 8 After writing to user registers Heater Current9 IHEAT Notes: 1. In Normal Mode, a temperature conversion is performed first, followed by an RH conversion. 2. In Fast Mode, both a temperature conversion and an RH conversion are initiated at the same time and occur in parallel. 3. Current consumption of RH conversion after the temperature conversion has finished. In Fast Mode, the temperature conversion finishes before the RH conversion. 4. Additional time for RH conversion after the temperature conversion has finished. 5. No conversion or I2C transaction in progress. Typical values measured at 25 °C. 6. Occurs once during powerup. Duration is <5 msec. 7. Occurs during I2C commands for Reset, Read/Write User Registers, Read EID, and Read Firmware Version. Duration is <100 μs when I2C clock speed is >100 kHz (>200 kHz for 2-byte commands). 8. IDD after a user register write. Initiating any other subsequent I2C transaction on the same bus (such as a user register read, starting an RH measurement, or traffic directed at other I2C devices) will transition the device to standby mode. 9. Additional current consumption when HTRE bit enabled. 4 Rev. 1.0 Si7034-A10 Table 2. General Specifications (Continued) 1.67 VDD 1.98 V; TA = –40 to +125 °C unless otherwise noted. Parameter Conversion Time Symbol Test Condition tCONV Normal Mode, RH conversion1 Typ Max Unit 5.8 8.5 ms 3.7 6 ms Fast Mode, parallel Temp and RH conversion2 0.9 1.5 ms Fast Mode, additional RH conversion time4 1.6 2.5 ms Normal Mode, Temperature conversion Powerup Time tPU Min 1 From VDD ≥ 1.67 V to ready for a conversion, 25 °C — 10 15 ms From VDD ≥ 1.67 V to ready for a conversion, full temperature range — — 50 ms After issuing a software reset command — 1.2 2.0 ms Notes: 1. In Normal Mode, a temperature conversion is performed first, followed by an RH conversion. 2. In Fast Mode, both a temperature conversion and an RH conversion are initiated at the same time and occur in parallel. 3. Current consumption of RH conversion after the temperature conversion has finished. In Fast Mode, the temperature conversion finishes before the RH conversion. 4. Additional time for RH conversion after the temperature conversion has finished. 5. No conversion or I2C transaction in progress. Typical values measured at 25 °C. 6. Occurs once during powerup. Duration is <5 msec. 7. Occurs during I2C commands for Reset, Read/Write User Registers, Read EID, and Read Firmware Version. Duration is <100 μs when I2C clock speed is >100 kHz (>200 kHz for 2-byte commands). 8. IDD after a user register write. Initiating any other subsequent I2C transaction on the same bus (such as a user register read, starting an RH measurement, or traffic directed at other I2C devices) will transition the device to standby mode. 9. Additional current consumption when HTRE bit enabled. Table 3. I2C Interface Specifications1 1.67 VDD 1.98 V; TA = –40 to +125 °C unless otherwise noted. Parameter Symbol Test Condition Min Typ Max Unit Hysteresis VHYS High-to-low versus low-to-high transition 0.05 x VDD — — V SCLK Frequency2 fSCL — — 400 kHz SCL High Time tSKH 0.6 — — µs SCL Low Time tSKL 1.3 — — µs Start Hold Time tSTH 0.6 — — µs Notes: 1. All values are referenced to VIL and/or VIH. 2. Depending on the conversion command, the Si7034 may hold the master during the conversion (clock stretch). At above 300 kHz SCL, the Si7034 may hold the master briefly for user register and device ID transactions. At the highest I2C speed of 400 kHz the stretching will be <50 µs. 3. Pulses up to and including 50 ns will be suppressed. Rev. 1.0 5 Si7034-A10 Table 3. I2C Interface Specifications1 (Continued) 1.67 VDD 1.98 V; TA = –40 to +125 °C unless otherwise noted. Parameter Symbol Test Condition Min Typ Max Unit Start Setup Time tSTS 0.6 — — µs Stop Setup Time tSPS 0.6 — — µs Bus Free Time tBUF 1.3 — — µs 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 µs SDA Acknowledge Valid Time tVD;ACK From SCL low to data valid — — 0.9 µs 50 — — ns Suppressed Pulse Width3 Between Stop and Start tSP Notes: 1. All values are referenced to VIL and/or VIH. 2. Depending on the conversion command, the Si7034 may hold the master during the conversion (clock stretch). At above 300 kHz SCL, the Si7034 may hold the master briefly for user register and device ID transactions. At the highest I2C speed of 400 kHz the stretching will be <50 µs. 3. Pulses up to and including 50 ns will be suppressed. tSKH 1/fSCL tSKL tSP SCL tBUF tSTH tDS D7 SDA D6 tDH D5 D0 tSPS R/W ACK Start Bit Stop Bit tVD : ACK tSTS Figure 1. I2C Interface Timing Diagram 6 Rev. 1.0 Si7034-A10 Table 4. Humidity Sensor 1.67 ≤ VDD ≤ 1.98 V; TA = 30 °C unless otherwise noted. Parameter Operating Accuracy Symbol Range1 2, 3 Test Condition Min Typ Max Unit Non-condensing 0 — 100 %RH 0 – 80% RH — ±3 +4 %RH %RH RMS 80 – 100% RH Repeatability/Noise4 See Figure 2 Normal — 0.15 — Fast — 0.45 — 1 m/s airflow — 18 — S Drift vs. Temperature — 0.05 — %RH/°C Hysteresis — ±1 — %RH — 0.25 — %RH/yr Response Time Long Term 5 τ63% Stability3 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 Relative Humidity Sensor Accuracy for more details. 3. Drift due to aging effects at typical room conditions of 30 °C and 30% to 50% RH. May be impacted by dust, vaporized solvents or other contaminants, e.g., out-gassing tapes, adhesives, packaging materials, etc. See section “4.7. Long Term Drift/Aging”. 4. 3-sigma measurement deviation. 5. Response time to a step change in RH. Time for the RH output to change by 63% of the total RH change. Figure 2. RH Accuracy at 30 °C Rev. 1.0 7 Si7034-A10 Table 5. Temperature Sensor 1.67 ≤ VDD ≤ 1.98 V; TA = –40 to +125 °C unless otherwise noted. Parameter Symbol Test Condition Operating Range Accuracy 1 Min Typ Max Unit –40 — +125 °C — ±0.3 ±0.4 °C °C RMS tA =30 °C –40 < tA < 125 °C Repeatability/Noise2 Response Time 3 τ63% Figure 3 Normal — 0.03 — Fast — 0.09 — Unmounted device — 0.7 — Si7034-EB — 5.1 — — < 0.01 — Long Term Stability Notes: 1. Normal conversion time. 2. 3-sigma measurement deviation. 3. 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 8 Rev. 1.0 s °C/Yr Si7034-A10 Table 6. Thermal Characteristics Parameter Symbol Test Condition QFN-6 Unit Junction to Air Thermal Resistance JA JEDEC 2-Layer Board, No Airflow 173 °C/W Junction to Air Thermal Resistance JA JEDEC 2-Layer Board, 1 m/s Airflow 153 °C/W Junction to Air Thermal Resistance JA JEDEC 2-Layer Board, 2 m/s Airflow 146 °C/W Junction to Case Thermal Resistance JC JEDEC 2-Layer Board 84 °C/W Junction to Board Thermal Resistance JB JEDEC 2-Layer Board 114 °C/W Table 7. Absolute Maximum Ratings1,2 Parameter Min Typ Max Unit Ambient temperature under bias –55 — 125 °C Storage Temperature –65 — 150 °C Voltage on I/O pins –0.3 — VDD+2.0 V V Voltage on VDD with Respect to GND –0.3 — 2.3 V HBM 2 kV CDM 1.25 kV MM 250 V ESD Tolerance Symbol Test Condition 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 application note, “AN607: Si70xx Humidity and Temperature Sensor Designer’s Guide”. Rev. 1.0 9 Si7034-A10 2. Typical Application Circuit The primary function of the Si7034 is to measure relative humidity and temperature. Figure 4 demonstrates the typical application circuit to achieve these functions; pins 3 and 6 are not required and must be left unconnected. Do not connect pins 3 and 6 to ground or pull up to VDD. They should be soldered to floating pads for mechanical stability of the package. 1 R1 10K DNC 6 1. to 1. V VDD GND SCL SDA 5 R2 10K Si7034 4 3 2 SCL DNC C1 0.1uF SDA Figure 4. Typical Application Circuit for Relative Humidity and Temperature Measurement 10 Rev. 1.0 Si7034-A10 3. Bill of Materials Table 8. Typical Application Circuit BOM for Relative Humidity and Temperature Measurement Reference Description Mfr Part Number Manufacturer R1 Resistor, 10 k, ±5%, 1/16W, 0402 CR0402-16W-103JT Venkel R2 Resistor, 10 k, ±5%, 1/16W, 0402 CR0402-16W-103JT Venkel C1 Capacitor, 0.1 µF, 6.3 V, X7R, 0402 C0402X7R6R3-104MNP Venkel U1 IC, Digital Temperature/humidity Sensor Si7034-A10-IM Silicon Labs Rev. 1.0 11 Si7034-A10 4. Functional Description Vdd Si7034 Humidity Sensor 1.25V Ref Calibration Memory Control Logic ADC Temp Sensor I2C Interface SDA SCL GND Figure 5. Si7034 Block Diagram The Si7034 is a digital relative humidity and temperature sensor that integrates temperature and humidity sensor elements, an analog-to-digital converter, signal processing, calibration, polynomial non-linearity correction, and an I2C interface all in a single chip. The Si7034 is individually factory-calibrated for both temperature and humidity, with the calibration data stored in on-chip non-volatile memory. This ensures that the sensor is fully interchangeable, with no recalibration or changes to software required. Patented use of industry-standard CMOS low-K dielectrics as a sensor enables the Si7034 to achieve excellent long term stability and immunity to contaminants with low drift and hysteresis. The Si7034 offers a low power, high accuracy, calibrated and stable solution ideal for a wide range of temperature, humidity, and dew-point applications including medical and instrumentation, high reliability automotive and industrial systems, and cost-sensitive consumer electronics. While the Si7034 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 as follows: The need to protect the sensor during board assembly, i.e., solder reflow, and the need to subsequently rehydrate the sensor. 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. 1.0 Si7034-A10 4.1. 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 25–30 °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 30 minutes before a reading is taken from the sensor. Prior to the sweep, the device is allowed to stabilize to 50%RH. The solid trace in Figure 6, “Measuring Sensor Accuracy Including Hysteresis,” shows the result of a typical sweep. Figure 6. Measuring Sensor Accuracy Including Hysteresis The RH accuracy is defined as the dotted 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 Si7034 accuracy specification (Table 4) includes: Unit-to-unit and lot-to-lot variation in non-linearity compensation Accuracy of factory calibration Margin for shifts that can occur during IR solder reflow (compensation for shift due to reflow is included in the linearization procedure below) The accuracy specification does not include: 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. RH readings will typically vary with temperature by < +0.05% / °C. Rev. 1.0 13 Si7034-A10 4.2. 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 trace in Figure 5. 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 error (dashed trace). In the example of Figure 5, the measurement uncertainty due to the hysteresis effect is +/-1.0%RH. 4.3. 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 “4.6. Bake/Hydrate Procedure” ). 4.4. PCB Assembly 4.4.1. Soldering Like most ICs, Si7034 devices are shipped from the factory vacuum-packed with an enclosed desiccant to avoid any RH accuracy drift during storage and to prevent any moisture-related issues during solder reflow. The following guidelines should be observed during PCB assembly: Si7034 devices are compatible with standard board assembly process. 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 AN607 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 polyimide tape can be installed during PCB assembly. 4.4.2. 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 Si7034 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. 4.4.3. 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: exposed polymer sensing film must be kept clean and undamaged. A Kapton® tape protective cover is recommended during any rework operation. 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 AN607 for more information on cleaning. The 14 Rev. 1.0 Si7034-A10 Minimize the heating of the device. Soldering iron temperatures should not exceed 350 °C and that the contact time per pin should not exceed 5 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. 4.5. 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. Depending on the needs of the application, there may be a need for basic protection against particulates or something more sophisticated such as a hydrophobic membrane providing up to IP67 compliant protection, during PCB assembly and/or the end system. 4.6. 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: the sensor at 125 °C for ≥ 12 hours Hydration 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. Baking 4.7. 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 Si7034 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 effects of damage, contamination, or exposure to extreme environmental conditions. Rev. 1.0 15 Si7034-A10 5. I2C Interface The Si7034 communicates with the Host controller over a digital I2C interface. The 7-bit base slave address is 0x70. Table 9. I2C Slave Address Byte A6 A5 A4 A3 A2 A1 A0 R/W 1 1 1 0 0 0 0 1/0 Master I2C devices communicate with the Si7034 using a command structure. The commands are listed in the I2C command table. Commands other than those documented below are undefined and should not be sent to the device. Table 10. I2C Command Table 16 Command Hold/No Hold Mode Hex Code Read Electronic ID: Two Separate IDs with checksum — 0xFA 0x0F Read Electronic ID: Two Separate IDs with checksum — 0xFC 0xC9 Soft Reset — 0xFE Temperature and Relative Humidity Measurement: Normal Mode Hold Mode 0x7C 0xA2 Temperature and Relative Humidity Measurement: Normal Mode No Hold Mode 0x78 0x66 Temperature and Relative Humidity Measurement: Fast Mode Hold Mode 0x64 0x58 Temperature and Relative Humidity Measurement: Fast Mode No Hold Mode 0x60 0x9C Query Device Device will ACK command, No Functional Effect or response 0x80 0x5D Query Device Response 0x00 0x47 0x2B 0xEF 0xC8 Write Heater Control Register Hold Mode 0xE6 Read Heater Control Register Hold Mode 0xE7 Read Firmware Revision — 0x84 0xF1 Rev. 1.0 Si7034-A10 5.1. Issuing a Measurement Command The measurement commands instruct the Si7034 to perform Relative Humidity and Temperature measurements. The procedure to issue any one of these commands is identical. While the measurement is in progress, the option of either clock stretching (Hold Master Mode) or Not Acknowledging read requests (No Hold Master Mode) is available to indicate to the master that the measurement is in progress; the chosen command code determines which mode is used. A checksum byte is returned from the slave for use in checking for transmission errors. The checksum byte will follow the least significant measurement byte. The checksum byte is calculated using a CRC generator polynomial of x8 + x5 + x4 + 1, with an initialization of 0xFC. Table 11. I2C Bit Descriptions Name Symbol Description START S SDA goes low while SCL high. STOP P SDA goes high while SCL high. Repeated START Sr SDA goes low while SCL high. It is allowable to generate a STOP before the repeated start. SDA can transition to high before or after SCL goes high in preparation for generating the START. READ R Read bit = 1 WRITE W Write bit = 0 All other bits — SDA value must remain high or low during the entire time SCL is high (this is the set up and hold time in Figure 1). In the I2C sequence diagrams in the following sections, bits produced by the master and slave are color coded as shown: Master Slave Sequence to perform a measurement and read back result (Hold Mode) Slave S R Address A W Command A Byte 1 Clock Stretch During Measurement Humidity MSB Temp MSB A Humidity LSB A A A Rev. 1.0 Command Byte 2 Temp LSB Checksum A Sr A NA Slave Address Checksum A P 17 Si7034-A10 Sequence to perform a measurement and read back result (No Hold Mode) Slave S R Address Sr NA* Command A W Slave Address Byte 1 R Humidity MSB A A A Temp MSB Humidity LSB A Command Byte 2 A A Temp LSB Checksum Slave Sr A NA Address Checksum A P *Note: Device will NACK the slave address byte until conversion is complete. 5.2. Reading and Writing User Registers The Heater Control Register allows the user to set the configuration of the Si7034. The procedure for accessing this register is described below. A checksum byte is not provided after reading a user register. Sequence to read a register S Slave Address Read W A Reg A Sr Cmd Slave Address R A Read Data NA Sequence to write a register S 18 Slave Address W A Write Reg Cmd Rev. 1.0 A Write Data A P P Si7034-A10 5.3. Measuring Relative Humidity Once a relative humidity measurement has been made, the results of the measurement may be converted to percent relative humidity by using the following expression: RH_Code%RH = 100 --------------------------16 2 Where: %RH is the measured relative humidity value in %RH RH_Code is the 16-bit word returned by the Si7034 5.4. Measuring Temperature Each time a relative humidity measurement is made a temperature measurement is also made for the purposes of temperature compensation of the relative humidity measurement.The results of the temperature measurement may be converted to temperature in degrees Celsius (°C) using the following expression: Temp_CodeT = – 45 + 175 --------------------------------16 2 Where: Temperature (°C) is the measured temperature value in °C Temp_Code is the 16-bit word returned by the Si7034 5.5. Firmware Revision The internal firmware revision can be read with the following I2C transaction: S Slave Address W A R 0x84 A A FWREV 0xF1 A NA A Sr Slave Address P The values in this field are encoded as follows: 0x10 = Firmware version 1.0 Rev. 1.0 19 Si7034-A10 5.6. Electronic Serial Number The Si7034 provides a serial number individualized for each device that can be read via the I2C serial interface. Two I2C commands are required to access the device memory and retrieve the complete serial number. The command sequence, and format of the serial number response is described in the figure below: Master Slave First access: S Slave Address W ACK 0xFA ACK 0X0F ACK S Slave Address R ACK SNA_3 ACK CRC ACK SNA_2 ACK CRC ACK SNA_1 ACK CRC ACK SNA_0 ACK CRC NACK S Slave Address W ACK 0xFC ACK 0XC9 ACK S Slave Address R ACK SNB_3 ACK SNB_2 ACK CRC ACK SNB_1 ACK SNB_0 ACK CRC NACK P 2nd access: P The format of the complete serial number is 64-bits in length, divided into 8 data bytes. The complete serial number sequence is shown below: SNA_3 SNA_2 SNA_1 SNA_0 SNB_3 SNB_2 SNB_1 SNB_0 The SNB3 field contains the device identification to distinguish between the different Silicon Labs relative humidity and temperature devices. The value of this field maps to the following devices according to this table: 0x00 or 0xFF engineering samples 0x22 = Si7034 5.7. Heater The Si7034 contains an integrated resistive heating element that may be used to raise the temperature of the sensor. This element can be used to test the sensor, to drive off condensation, or to implement dew-point measurement when the Si7034 is used in conjunction with a separate temperature sensor such as another Si7034 (the heater will raise the temperature of the internal temperature sensor). The heater can be activated using HTRE, bit 4 in the Heater Control Register. Turning on the heater will reduce the tendency of the humidity sensor to accumulate an offset due to “memory” of sustained high humidity conditions. The heater current can be configured using bits 3:0 of the Heater Control Register. 20 Rev. 1.0 Si7034-A10 6. Control Registers Table 12. Register Summary Register Bit 7 Bit 6 Heater Control Register Bit 5 Bit 4 RSVD Bit 3 Bit 2 HTRE Bit 1 Bit 0 HEATER[3:0] Notes: 1. Any register not listed here is reserved and must not be written.The result of a read operation on these registers is undefined. 2. Except where noted, reserved register bits will always read back as “1,” and are not affected by write operations. For future compatibility, it is recommended that prior to a write operation, registers should be read. Then the values read from the RSVD bits should be written back unchanged during the write operation. Register 1. Heater Control Register Bit D7 Name D6 D5 D4 RSVD Type D3 D2 HTRE D1 D0 Heater [3:0] R/W R/W Reset Settings = 0000_0000 Bit D4 Name HTRE D3:D0 HEATER[3:0] Function 1 = On-chip Heater Enable 0 = On-chip Heater Disable D3 D2 D1 D0 Heater Current 0 0 0 0 6.4 mA 0 0 0 1 9.7 mA 0 0 1 0 13.1 mA 0 19.6 mA 0 32.4 mA 1 53.5 mA ... 0 1 0 ... 1 0 0 ... 1 D7,D6, D5 RSVD 1 1 Reserved Rev. 1.0 21 Si7034-A10 7. Pin Descriptions: Si7034 (Top View) DNC VDD 1 SCL 2 6 3 5 GND 4 SDA DNC Pin Name Pin # VDD 1 Power. This pin is connected to the power supply on the circuit board. SCL 2 I2C clock DNC 3,6 SDA 4 I2C data GND 5 Ground. This pin is connected to ground on the circuit board. 22 Pin Description Do not connect electrically. It is recommended to solder to floating pads for mechanical stability. Do not connect to GND or GND plane. Rev. 1.0 Si7034-A10 8. Ordering Guide Table 13. Device Ordering Guide P/N Description Max. Accuracy Temp RH Package Operating Range (°C) Packing Format Si7034-A10-IM Digital temperature/ humidity sensor ±0.4 °C ± 4% 6-pin QFN –40 to +125 °C Cut tape Si7034-A10-IMR Digital temperature/ humidity sensor ±0.4 °C ± 4% 6-pin QFN –40 to +125 °C Tape-and-reel Rev. 1.0 23 Si7034-A10 9. Package Outline 9.1. Package Outline: 2x2 6-pin QFN Figure 7 illustrates the package details for the Si7034. Figure 7. Si7034 Package Drawing Table 14. Package Dimensions Dimension Min Nom Max A 0.70 0.75 0.80 b 0.30 0.35 0.40 D 2.00 BSC E 2.00 BSC e 1.00 BSC D2 0.60 0.70 0.80 E2 1.50 1.60 1.70 g 0.20 0.25 0.30 H1 0.70 0.75 0.80 H2 1.20 1.25 1.30 L 0.30 0.35 0.40 aaa 0.10 bbb 0.10 ccc 0.08 ddd 0.10 eee 0.05 fff 0.05 Notes: 1. All dimensions shown are in millimeters (mm). 2. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 24 Rev. 1.0 Si7034-A10 10. PCB Land Pattern and Solder Mask Design Figure 8. PCB Land Pattern Dimensions Table 15. PCB Land Pattern Dimensions Symbol mm C1 2.00 E 1.00 X1 0.40 Y1 0.75 X2 1.70 Y2 0.80 Notes: General 1. All dimensions shown are in millimeters (mm). 2. This Land Pattern Design is based on the IPC-7351 guidelines. 3. All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition (LMC) is calculated based on a Fabrication Allowance of 0.05 mm. Solder Mask Design 4. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60 µm minimum, all the way around the pad. Stencil Design 5. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 6. The stencil thickness should be 0.125 mm (5 mils). 7. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pins. 8. A 2x1 array of 0.55 mm square openings on 0.90 mm pitch should be used for the center ground pad to achieve a target solder coverage of 50%. Card Assembly 9. A No-Clean, Type-3 solder paste is recommended. 10. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. Rev. 1.0 25 Si7034-A10 11. Top Marking 11.1. Si7034 Top Marking 11.2. Top Marking Explanation 26 Mark Method: Laser Font Size: 0.30 mm Line 1 Marking: Circle = 0.25 mm Diameter, Pin #1 Indicator T = Manufacturing Trace Code Digit 1 Line 2 Marking: TT = Manufacturing Trace Code Digits 2-3 Rev. 1.0 Si7034-A10 12. Additional Reference Resources AN607: Si70xx Humidity and Temperature Sensor Designer’s Guide Rev. 1.0 27 Si7034-A10 DOCUMENT CHANGE LIST Revision 0.5 to Revision 0.8 Revision 0.11 to Revision 0.3 Updates to Section 1. “Electrical Specifications”. Updated Table 2. “General Specifications”. 2 Updated Figure 1. “I C Interface Timing Diagram”. Updated Table 12. “I2C Command Table”. Updated Section 4.4. “PCB Assembly”. Updated Section 5.2. “Reading and Writing User Registers”. Updated Section 5.3. “Measuring Relative Humidity”. Updated Section 5.4. “Measuring Temperature”. Updated Section 5.6. “Electronic Serial Number”. Updated Section 6. “Control Registers”. Updated Section 7. “Pin Descriptions”. Updated Section 8. “Package Outline”. Revision 0.8 to Revision 0.9 Revision 0.3 to Revision 0.4 Updated Features on page 1. Updated Block Diagram. Updated Table 1. Updated Table 2. Updated Table 3. Updated Table 4. Updated Table 5. Updated Table 6. Updated Table 7. Updated Table 8. Updated Section 4.4. Updated Table 12. Updated Section 5. Added Section 6. Updated Table 13. Updated Section 9. Updated Section 10. 28 Updated Table 2. Updated footnotes in Table 3. Updated Table 4. Updated descriptions in Table 10. Updated Table 13. Updated Section 5.1. Updated Section 5.3. Added Section 5.5. Updated Section 6. Revision 0.9 to Revision 1.0 Updated features on page 1. Updated Table 2. Updated Figure 4 Updated Section 5.1. Revision 0.4 to Revision 0.5 Updated Table 6, “Thermal Characteristics,” on page 9. Updated Table 2. Updated Table 10. Updated Section 5.3. Updated Section 5.4. Updated Section 11. Added ESD specifications to Table 7. Revised Heater Control Register settings. Updated Firmware Revision command address. Corrected pin numbering in Figure 7 and Figure 8. Updated Table 4, “Humidity Sensor,” on page 7. Updated Table 5, “Temperature Sensor,” on page 8. Changed power supply voltage range to ±10%. Rev. 1.0 Smart. Connected. Energy-Friendly. Products Quality Support and Community www.silabs.com/products www.silabs.com/quality community.silabs.com Disclaimer Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products are not designed or authorized to be used within any Life Support System without the specific written consent of Silicon Laboratories. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected to result in significant personal injury or death. Silicon Laboratories products are not designed or authorized for military applications. Silicon Laboratories products shall under no circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons. Trademark Information Silicon Laboratories Inc.® , Silicon Laboratories®, Silicon Labs®, SiLabs® and the Silicon Labs logo®, Bluegiga®, Bluegiga Logo®, Clockbuilder®, CMEMS®, DSPLL®, EFM®, EFM32®, EFR, Ember®, Energy Micro, Energy Micro logo and combinations thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZRadio®, EZRadioPRO®, Gecko®, ISOmodem®, Precision32®, ProSLIC®, Simplicity Studio®, SiPHY®, Telegesis, the Telegesis Logo®, USBXpress® and others are trademarks or registered trademarks of Silicon Laboratories Inc. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of ARM Holdings. Keil is a registered trademark of ARM Limited. All other products or brand names mentioned herein are trademarks of their respective holders. Silicon Laboratories Inc. 400 West Cesar Chavez Austin, TX 78701 USA http://www.silabs.com