SHT15

SHT1x / SHT7x Humidity & Temperature Sensor Evaluation Kit Available SHT7x SHT1x - Relative humidity and temperature sensors - Dew point - Fully calibrated, digital output - Excellent long-term stability - No external components required - Ultra low power consumption - Surface mountable or 4-pin fully interchangeable - Small size - Automatic power down SHT1x / SHT7x Product Summary The SHTxx is a single chip relative humidity and temperature multi sensor module comprising a calibrated digital output. Application of industrial CMOS processes with patented micro-machining (CMOSens® technology) ensures highest reliability and excellent long term stability. The device includes a capacitive polymer sensing element for relative humidity and a bandgap temperature sensor. Both are seamlessly coupled to a 14bit analog to digital converter and a serial interface circuit on the same chip. This results in superior signal quality, a fast response time and insensitivity to external disturbances (EMC) at a very competitive price. Each SHTxx is individually calibrated in a precision humidity chamber with a chilled mirror hygrometer as reference. The calibration coefficients are programmed into the OTP memory. These coefficients are used internally during measurements to calibrate the signals from the sensors. The 2-wire serial interface and internal voltage regulation allows easy and fast system integration. Its tiny size and low power consumption makes it the ultimate choice for even the most demanding applications. The device is supplied in either a surface-mountable LCC (Leadless Chip Carrier) or as a pluggable 4-pin single-in-line type package. Customer specific packaging options may be available on request. Applications _ HVAC _ Automotive _ Consumer Goods _ Weather Stations _ Humidifiers _ Dehumidifiers _ Test & Measurement _ Data Logging _ Automation _ White Goods _ Medical Block Diagram 1 %RH Sensor Calibration Memory SCK DATA Digital 2wire Interface & CRC generator GND Temp. Sensor VDD Amplification D Ordering Information Humidity Temperature Part accuracy accuracy [K] Package Number [%RH] @ 25 °C SHT11 SHT15 SHT71 SHT75 ±3.0 ±2.0 ±3.0 ±1.8 ±0.4 ±0.3 ±0.4 ±0.3 SMD (LCC) SMD (LCC) 4-pin single-in-line 4-pin single-in-line A i -b 14 t www.sensirion.com Sensirion, Eggbühlstr. 14, 8052 Zürich, Switzerland, Tel: +41 1 306 40 00, Fax: +41 1 306 40 30 v2.02 SHT1x / SHT7x Relative Humidity & Temperature Sensor System 1 Sensor Performance Specifications Conditions Min. Typ. Max. Units 0.5 8 linearized 0.03 0.03 12 12 ±0.1 see figure 1 %RH bit %RH %RH ±5 ±4 ±3 ±2 ±1 ±0 Relative Humidity absolute accuracy Parameter Humidity Resolution (2) Repeatability Accuracy (1) Uncertainty Interchangeability Nonlinearity Range Response time Hysteresis Long term stability Temperature Resolution (2) SHT11/71 SHT15 SHT75 0 10 20 30 40 50 60 70 80 90 100 %RH raw data linearized 1/e (63%) typical slowly moving air Fully interchangeable %RH ±3 2.47 ‘1’ for Vdd < 2.47 reserved reserved For Testing only, do not use Heater no reload from OTP ’1’ = 8bit RH / 12bit Temperature resolution ’0’ = 12bit RH / 14bit Temperature resolution Default 0 X No default value, bit is only updated after a measurement 0 0 0 0 off 0 reload 0 12bit RH 14bit Temp. 5 4 3 2 1 0 Table 4 SHTxx DC Characteristics R/W R/W R/W Table 3 Status Register Bits 2.3.1 Measurement resolution The default measurement resolution of 14bit (temperature) and 12bit (humidity) can be reduced to 12 and 8bit. This is especially useful in high speed or extreme low power applications. Conditions Min Typ. Max. Unit FSCK VDD > 4.5 V 10 MHz VDD < 4.5 V 1 MHz TRFO DATA fall time Output load 5 pF 3.5 10 20 ns Output load 100 pF 30 40 200 ns TCLx SCK hi/low time 100 ns TV DATA valid time 250 ns TSU DATA set up time 100 ns THO DATA hold time 0 10 ns TR/TF SCK rise/fall time 200 ns Parameter SCK frequency 2.3.2 End of Battery The “End of Battery” function detects VDD voltages below 2.47 V. Accuracy is ±0.05 V Table 5 SHTxx I/O Signals Characteristics TCLH FSCK TR TF 2.3.3 Heater An on chip heating element can be switched on. It will increase the temperature of the sensor by 5-15 °C (9-27 °F). Power consumption will increase by ~8 mA @ 5 V. Applications: By comparing temperature and humidity values before and SCK TV TSU DATA THO Figure 9 Timing Diagram 1) (2) (3) Parameters are periodically sampled and not 100% tested With one measurement of 8 bit accuracy without OTP reload per second With one measurement of 12bit accuracy per second www.sensirion.com v2.02 July 2004 4/9 ack TS SHT1x / SHT7x Relative Humidity & Temperature Sensor System 3 Converting Output to Physical Values 3.2 Temperature The bandgap PTAT (Proportional To Absolute Temperature) temperature sensor is very linear by design. Use the following formula to convert from digital readout to temperature: 3.1 Relative Humidity To compensate for the non-linearity of the humidity sensor and to obtain the full accuracy it is recommended to convert the readout with the following formula1: RHlinear = c 1 + c 2 • SORH + c 3 • SORH 2 SORH c1 c2 c3 12 bit -4 0.0405 -2.8 * 10-6 8 bit -4 0.648 -7.2 * 10-4 Table 6 Humidity conversion coefficients Temperature = d1 + d 2 • SOT For simplified, less computation intense conversion formulas see application note “RH and Temperature Non-Linearity Compensation”. The humidity sensor has no significant voltage dependency.  & $ "   VDD 5V 4V 3.5V 3V 2.5V Table 8 d1 [°C] d1 [°F] SOT d2 [°C] d2 [°F] -40.00 -40.00 14bit 0.01 0.018 -39.75 -39.50 12bit 0.04 0.072 -39.66 -39.35 -39.60 -39.28 -39.55 -39.23 Temperature conversion coefficients For improved accuracies in extreme temperatures with more computation intense conversion formulas see application note “RH and Temperature Non-Linearity Compensation”. %RH 3.3 Dewpoint Since humidity and temperature are both measured on the same monolithic chip, the SHTxx allows superb dewpoint measurements. See application note “Dewpoint calculation” for more.  # SORH sensor readout (12bit)  #  # ! Figure 10 Conversion from SORH to relative humidity 3.1.1 Humidity Sensor RH/Temperature compensation For temperatures significantly different from 25 °C (~77 °F) the temperature coefficient of the RH sensor should be considered: RHtrue = (T°C - 25) • (t1 + t 2 • SORH ) + RHlinear SORH t1 t2 12 bit 0.01 0.00008 8 bit 0.01 0.00128 Table 7 Temperature compensation coefficients This equals ~0.12 %RH / °C @ 50 %RH 1 Where SORH is the sensor output for relative humidity www.sensirion.com v2.02 July 2004 5/9 SHT1x / SHT7x Relative Humidity & Temperature Sensor System 4 100 80 60 40 20 Applications Information 4.6 Light The SHTxx is not light sensitive. Prolonged direct exposure to sunshine or strong UV radiation may age the housing. [%RH] Maximum operating conditions 4.1 Operating and Storage Conditions Normal operating conditions [°C] 4.7 Materials Used for Sealing / Mounting 0 -40 -20 0 20 40 60 80 100 120 Figure 11 Recommended operating conditions Conditions outside the recommended range may temporarily offset the RH signal up to ±3 %RH. After return to normal conditions it will slowly return towards calibration state by itself. See 4.3 “Reconditioning Procedure” to accelerate this process. Prolonged exposure to extreme conditions may accelerate ageing. Many materials absorb humidity and will act as a buffer, increasing response times and hysteresis. Materials in the vicinity of the sensor must therefore be carefully chosen. Recommended materials are: All Metals, LCP, POM (Delrin), PTFE (Teflon), PE, PEEK, PP, PB, PPS, PSU, PVDF, PVF For sealing and gluing (use sparingly): High filled epoxy for electronic packaging (e.g. glob top, underfill), and Silicone. Outgassing of these materials may also contaminate the SHTxx (cf. 4.2). Store well ventilated after manufacturing or bake at 50°C for 24h to outgas contaminants before packing. 4.2 Exposure to Chemicals Chemical vapors may interfere with the polymer layers used for capacitive humidity sensors. The diffusion of chemicals into the polymer may cause a shift in both offset and sensitivity. In a clean environment the contaminants will slowly outgas. The reconditioning procedure described below will accelerate this process. High levels of pollutants may cause permanent damage to the sensing polymer. 4.8 Wiring Considerations and Signal Integrity Carrying the SCK and DATA signal parallel and in close proximity (e.g. in wires) for more than 10cm may result in cross talk and loss of communication. This may be resolved by routing VDD and/or GND between the two data signals. Please see the application note “ESD, Latchup and EMC” for more information. Power supply pins (VDD, GND) should be decoupled with a 100 nF capacitor if wires are used. 4.3 Reconditioning Procedure The following reconditioning procedure will bring the sensor back to calibration state after exposure to extreme conditions or chemical vapors. 80-90 °C (176-194°F) at < 5 %RH for 24h (baking) followed by 20-30 °C (70-90°F) at > 74 %RH for 48h (re-hydration) 4.9 Qualifications Extensive tests were performed in various environments. Please contact SENSIRION for detailed information. Environment Temperature Cycles HAST Pressure Cooker High Temperature and Humidity Salt Atmosphere Condensing Air Freezing cycles fully submerged Various Automotive Chemicals Table 9 Norm JESD22-A104-B -40 °C / 125 °C, 1000 cy JESD22-A110-B 2.3 bar 125 °C 85 %RH JESD22-A101-B 85 °C 85 %RH 1250h DIN-50021ss -20 / +90 °C, 100 cy 30min dwell time DIN 72300-5 Results(1) Within Specifications Reversible shift by +2 %RH Reversible shift by +2 %RH Within Spec. Within Spec. Reversible shift by +2 %RH Within Specifications 4.4 Temperature Effects The relative humidity of a gas strongly depends on its temperature. It is therefore essential to keep humidity sensors at the same temperature as the air of which the relative humidity is to be measured. If the SHTxx shares a PCB with electronic components that give off heat it should be mounted far away and below the heat source and the housing must remain well ventilated. To reduce heat conduction copper layers between the SHT1x and the rest of the PCB should be minimized and a slit may be milled in between (see figure 13). Qualification tests (excerpt) 4.5 Membranes A membrane may be used to prevent dirt from entering the housing and to protect the sensor. It will also reduce peak concentrations of chemical vapors. For optimal response times air volume behind the membrane must be kept to a minimum. For the SHT1x package Sensirion recommends the SF1 filter cap for optimal IP67 protection. (1) 4.10 ESD (Electrostatic Discharge) ESD immunity is qualified according to MIL STD 883E, method 3015 (Human Body Model at ±2 kV)). Latch-up immunity is provided at a force current of ±100 mA with Tamb = 80 °C according to JEDEC 17. See application note “ESD, Latchup and EMC” for more information. The temperature sensor passed all tests without any detectable drift. Package and electronics also passed 100% www.sensirion.com v2.02 July 2004 6/9 SHT1x / SHT7x Relative Humidity & Temperature Sensor System 5 Pin 1 2 3 4 Package Information Name GND DATA SCK VDD NC Comment Ground Serial data, bidirectional Serial clock, input Supply 2.4 - 5.5 V Remaining pins must be left unconnected For manual soldering contact time must be limited to 5 seconds at up to 350 °C. After soldering the devices should be stored at >74 %RH for at least 24h to allow the polymer to rehydrate. Please consult the application note “Soldering procedure” for more information. 5.1 SHT1x (surface mountable) Table 10 SHT1x Pin Description 5.1.4 Mounting Examples 5.1.1 Package type The SHT1x is supplied in a surface-mountable LCC (Leadless Chip Carrier) type package. The sensors housing consists of a Liquid Crystal Polymer (LCP) cap with epoxy glob top on a standard 0.8 mm FR4 substrate. The device is free of lead, Cd and Hg. Device size is 7.42 x 4.88 x 2.5 mm (0.29 x 0.19 x 0.1 inch) Weight 100 mg The production date is printed onto the cap in white numbers in the form wwy. e.g. ”351” = week 35, 2001. Slit to minimize heat transfer from the PCB Figure 13 SHT1x PCB Mounting example 5.1.2 Delivery Conditions The SHT1x are shipped in 12mm tape at 100pcs or 400pcs.. Reels are individually labelled with barcode and human readable labels. The Lot numbers allow full traceability through production, calibration and test. 2.8mm The SF1 membrane filter cap is available for optimal IP67 protection. When mounted through a housing the interior can be protected from the environment while still allowing high quality humidity measurements (see example below). o-ring housing housing Filtercap SH 1x T Carrier Tape Cover Tape Trailer Tape 300mm minimum Components Leader Tape 480mm minimum PCB melted plastic pin Figure 12 Tape configuration and unit orientation 5.1.3 Soldering Information Standard reflow soldering ovens may be used. For details please see application note "soldering procedure". Top View 1.15 (0.04) NC 1.9 (0.07) 1.49 (0.06) Figure 14 SF1 IP67 filter cap mounting example Side View sensor opening NC NC NC NC NC Recommended PCB Footprint 7.42 (0.29) 6.88 (0.27) 1.81 1.27 (0.07) (0.05) 2.5 (0.1) 5.22 (0.2) 2.44 (0.1) 4.88 (0.19) 0.8 (0.03) 4 3.99 (0.16) 3 0.8 (0.03) 0.47 (0.018) 2 actual size 1.8 (0.07) 3.48 (0.137) 7.08 (0.278) 1.8 (0.07) Figure 15 SHT1x drawing and footprint dimensions in mm (inch) www.sensirion.com v2.02 July 2004 1.27 1.27 1.27 (0.05) 1 No copper inside this field 0.6 (0.02) 4.61 (0.2) 7/9 SHT1x / SHT7x Relative Humidity & Temperature Sensor System 5.2 SHT7x (4-pin single-in-line) Pin 1 2 3 4 Name SCK VDD GND DATA Comment Serial clock input Supply 2.4 - 5.5 V Ground Serial data bidirectional 3.7 (0.15) 0.4 (0.02) 3.1 (0.12) 2.2 (0.09) Table 11 SHT7x Pin Description 5.2.1 Package type1 The device is supplied in a single-in-line pin type package. The sensor housing consists of a Liquid Crystal Polymer (LCP) cap with epoxy glob top on a standard 0.6 mm FR4 substrate. The device is Cd and Hg free. The sensor head is connected to the pins by a small bridge to minimize heat conduction and response times. The gold plated back side of the sensor head is connected to the GND pin. A 100nF capacitor is mounted on the back side between VDD and GND. All pins are gold plated to avoid corrosion. They can be soldered or mate with most 1.27 mm (0.05’’) sockets e.g.: Preci-dip / Mill-Max 851-93-004-20-001 or similar Total weight: 168 mg, weight of sensor head: 73 mg The production date is printed onto the cap in white numbers in the form wwy. e.g. ”351” = week 35, 2001. 13.5 (0.53) 3.7 (0.15) 1.2 (0.05) 0.6 (0.024) 1 2 3 4 3.4 (0.13) ~6 (~0.24) 5.2.2 Delivery Conditions The SHT7x are shipped in 32 mm tape. These reeled parts in standard option are shipped with 500 units per 13 inch diameter reel. Reels are individually labelled with barcode and human readable labels. 0.46 1.27 (0.018) 5.08 (0.05) (0.2) 0.2 (0.01) 2 (0.08) Figure 17 SHT7x dimensions in mm (inch) Carrier Tape Cover Tape Trailer Tape 300mm minimum Components Leader Tape 500mm minimum Figure 16 Tape configuration and unit orientation 5.2.3 Soldering Information2 Standard wave SHT7x soldering ovens may be used at maximum 235 °C for 20 seconds. For manual soldering contact time must be limited to 5 seconds at up to 350 °C. After wave soldering the devices should be stored at >74 %RH for at least 24 h to allow the polymer to rehydrate. Please consult the application note “Soldering procedure” for more information. Other packaging options may be available on request. For maximum accuracy do not solder SHT75! www.sensirion.com 1 2 v2.02 July 2004 8/9 SHT1x / SHT7x Relative Humidity & Temperature Sensor System 6 Revision history Version Page(s) Preliminary 1-9 Preliminary Final v2.0 1-9 V2.01 V2.02 1-9 1-9 Changes First public release Added SHT7x information Major remake, added application information etc. Various small modifications Typos, Graph labeling Improved specifications, added SF1 information, improved wording Date February 2002 June 2002 March 2003 July 2004 The latest version of this document and all application notes can be found at: www.sensirion.com/en/download/humiditysensor/SHT1x_SHT7x.htm 7 Important Notices 7.3 Warranty SENSIRION AG makes no warranty, representation or guarantee regarding the suitability of its product for any particular purpose, nor does SENSIRION AG assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability, including without limitation consequential or incidental damages. “Typical” parameters can and do vary in different applications. All operating parameters, including “Typical” must be validated for each customer applications by customer’s technical experts. SENSIRION AG reserves the right, without further notice, to change the product specifications and/or information in this document and to improve reliability, functions and design. Copyright© 2001-2004, SENSIRION AG. All rights reserved. 7.1 Warning, personal injury Do not use this product as safety or emergency stop devices or in any other application where failure of the product could result in personal injury. Failure to comply with these instructions could result in death or serious injury. Should buyer purchase or use SENSIRION AG products for any such unintended or unauthorized application, Buyer shall indemnify and hold SENSIRION AG and its officers, employees, subsidiaries, affiliates and distributors harmless against all claims, costs, damages and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SENSIRION AG was negligent regarding the design or manufacture of the part. 7.2 ESD Precautions The inherent design of this component causes it to be sensitive to electrostatic discharge (ESD). To prevent ESD-induced damage and/or degradation, take normal ESD precautions when handling this product. See application note “ESD, Latchup and EMC” for more information. Headquarters and Sales Office SENSIRION AG Eggbühlstr. 14 P.O. Box CH-8052 Zürich Switzerland Phone: + 41 (0)44 306 40 00 Fax: + 41 (0)44 306 40 30 e-mail: info@sensirion.com http://www.sensirion.com/ Sensirion humidity sensors are available from: find your local representative at: www.sensirion.com/reps www.sensirion.com v2.02 July 2004 9/9