PRELIMINARY! DIGITAL HUMIDITY SENSOR

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1 Characteristic features Measuring range % rh, C Calibrated and temperature-compensated Accuracy ±1.8 % RH and ±0.2 C (-H) Chemical resistant, dew formation resistant Low hysteresis, compensated linearity error and temperature drift Operating voltage V Current consumption < 1µA (25 C, sleep-mode) Digital I²C Interface for µc High quality ceramic substrate SIL-connections, plug-in type, pitch 1.27 mm iaturized construction, fully replaceable Mechanically robust Optimum price performance ratio RoHS conformance ical areas of application Automotive Household appliances Consumer products Air-conditioning Instrumentation Features The combines the advantages of a precise, capacitive humidity sensor with the high integration density and functionality of an ASIC. The signal processing, integrated in the sensor, processes the humidity and temperature provides digital values over the I 2 C compatible interface. The module is factory calibrated and any further alignment by the user is not necessary. Both linearity error and temperature drift are corrected on the chip internally, hence excellent accuracy is achieved over a wide operating range. Compared to monolithic solutions, the offers crucial advantages. The applied sensor corresponds to the proven, capacitive versions of the HS series in terms of quality and layer construction. Also, offers identical outstanding characteristics because of the use of same high performance polymer. The sensor has a high chemical resistance and excellent long term stability, even in critical application areas with high humidity. The sensor is dew resistant. The plug-in type calibrated component has SIL-connection pins with a pitch of 1.27 mm which are compatible with commercial connectors. Thus, the sensor without calibration is fully interchangeable. Other variants, for example as SMD version, are also available on request. Technical Data Humidity Sensor Measuring principle Humidity measuring range Humidity accuracy Humidity resolution Hysteresis Linearity error Response time t63 Capacitive polymer Humidity sensor % rh. (max. dp = +80 C) -S ±2.8% rh -H ±1.8% rh 0.02% rh < ±1% rh < ±1% rh < 4 sec Temp. measuring range C Temperature accuracy -S ±0.3 C -H ±0.2 C Temperature resolution C Digital interface Operating voltage Current consumption (nominal) Dimensions Connection I 2 C, Address 0x28 Alternative address V < 1µA in standby mode < 33µA at 1Hz meas. rate 850 µa maximum 5.08 x x 2.0 mm SIL RM 1.27 mm RoHS-Conformance Example source code and PC-based evaluation kit are available on request! Page 1/6

2 Housing and materials The ASIC, together with the sensor element, is mounted on the ceramic substrate with dimensions 5.08 x Up to the active layer of the sensor element, the ASIC is environmentally resistant. The connections pins are made up of a Cu-Be alloy and tinned. All materials are optimised for minimum water absorption, so that the micro-climate in the environment is not disturbed. The application and temperature range of C are covered by the materials used. All materials correspond to EG-guidelines 2002/95/EG and are RoHS conforming. None of the prohibited materials Pb, Cd, Hg, Cr(6+) PBB or PBDE are contained in the module. There are two SMD capacitors on the module for decoupling. These components are also meet RoHS conform. Internal Functionality of the ASIC The ASIC consists internal of a capacitance to digital converter (14 bits), a polynomial signal processor, a coefficient memory for the calibration values and digital I 2 C-Interface. The correction algorithms implemented in the ASIC work by means of 2nd order polynomials and ensure the computational correction of offset, gain and linearity behaviour, as well as the temperature drift. Because of this, the application window is extremely wide and is accurate from 0 100% rh in the temperature range of C with a maximum dew point of 80 C. The sensor supplies the completely processed values of relative humidity and temperature in digital outputs through the I 2 C Interface. Digital I 2 C-Interface The digital interface fully corresponds to the I 2 C- standard and can be used together with other I 2 C components. In addition to the fixed assigned address 0x28, a second address can also be defined. Thus, simultaneous operation of up to 126 sensors is possible with the same I 2 C bus. Figure: Measurements in mm (1mm = inch) Assignment of pins: 1: SDA, 2: GND, 3: VDD, 4: SCL Cleaning For drying or removing dust particles, the sensor may be blown off with pure clean air. The sensor may be cleaned in isopropanol at 23 C. Then, it must be rinsed several times, either in Isopropyl alcohol or in distilled water with max 15 µs conductivity. Subsequently, the sensor is to be dried with clean compressed air followed by heating in the oven at 60 C/24h. The application of ultrasonic cleaning is not allowed. Mounting The component is provided with connection pins and can be inserted into commercial plug connectors with pitch 1.27 mm. Direct soldering into printed circuits is possible, however, it is not recommended because there is a danger of the sensitive sensor surface becoming damaged by splashing of solder or fluxing agent. While inserting into the contacts, care should be taken to hold the sensor only from the sides at the edge. Touching the sensor surface is not allowed. Page 2/6

3 IC Characteristics Absolute maximum ratings Analog Supply Voltage (VDD Mode) V DD V Voltages at Analog I/O In Pin V INA -0.3 V DD+0.3 V Voltages at Analog I/O Out Pin V OUTA -0.3 V DD+0.3 V Storage Temperature Range ( 10 hours) T STOR C Storage Temperature Range (<10 hours) T STOR<10h C Recommended operating conditions Supply Voltage to Gnd (Supply = VDD pin) 1, 2 V SUPPLY V Ambient Temperature Range T AMB C Pull-up on SDA and SCL R PU kω Electrical parameters Supply Current (varies with sample rate) I DD Conditions maximum sample rate Supply Current I DD 1Hz sample rate Supply Sleep Mode Current I sleep C 1 5 µa C 10 µa I 2 C - Interface Voltage Level Low V OL VSUPPLY Voltage Level High V OH VSUPPLY Voltage Level Low V IL VSUPPLY Voltage Level High V IH VSUPPLY Total system Frequency Variation f var By design ±15 % Start-Up-Time Power-on (POR) to data ready t STA slowest settings µa µa 155 ms Sampling Rate t rate 14 bit 18.5 ms Page 3/6

4 Accuracy Relative Humidity Humidity measurement Conditions Resolution Bit RES Bit Bits Resolution % RES % % RH Accuracy -S (1) ERR % 33 / 75 % RH ±2.8 % RH Accuracy -H (1) ERR % 33 / 75 % RH ±1.8 % RH Repeatebility (2) REP % 33% RH ±0.1 %RH Replacement fully interchangeable without calibration Hysteresis HYST % 33% RH ±1 % RH Nonlinearity NL < 1 % RH Response time t66 RT t63 4 s RH operating range (3) RNG RH % RH T operating range (3) RNG T C Long term drift DRIFT < 0.5 %/year (1) Accuracy is tested at 23 C and 3.3 V in rising dir ection. It does not include hysteresis and non linearity. (2) Repeatebility is measured in same direction without Hysteresis effects (3) imum dewpoint is limited to 80 C. Accuracy Temperature Conditions Temperature conversion Resolution Bit RES Bit Bits Resolution in C RES % C Accuracy -S ERR % 23 C ±0.3 C Accuracy -H ERR % 23 C ±0.2 C Repeatebility REP % 23 C ±0.05 C Replacement fully interchangeable without calibration Response time t66 RT t63 10 s Operation range RNG T C Long term drift DRIFT < 0.03 C/year Page 4/6

5 I 2 C Interface and Timing For integration with the micro-controller, the Humidity module has a I 2 C-compatible interface which supports both 100 khz and 400 khz bit rate. The I 2 C slave address is programmed by default on 0x28 and can be adjusted in the entire address range of (0x00 to 0x7F). Hence, up to 126 Humidity modules can be operated on a single I 2 C-Bus. PARAMETER SYMBOL MIN MAX UNIT SCL clock frequency fscl khz Start condition hold time relative to SCL edge imum SCL clock low width 1 imum SCL clock high width 1 Start condition setup time relative to SCL edge Data hold time on SDA relative to SCL edge Data setup time on SDA relative to SCL edge Stop condition setup time on SCL thdsta 0.1 µs tlow 0.6 µs thigh 0.6 µs tsusta 0.1 µs thddat 0 µs tsudat 0.1 µs tsusto 0.1 µs There are two I 2 C commands for the user to access the humidity module: Command 'Data Fetch' (DF) 'Measuring Request' (MR) Description Fetch the last measured value of Humidity/ Temperature Start a measuring cycle In the initial condition, the humidity module is in the Sleep mode to minimise on the current consumption. A new measurement is carried out only after the command measuring request (MR) is received. Access to the status bits and measured values is made by the data fetch command. After the measuring cycle has been completely processed, the ready status bit is set and the current measured values are available. To determine if the measuring cycle has been already finished, the output registers may be cyclically polled. If the access to the measured values takes place too early, then the measured values of the previous measuring cycle are transferred and the stale status bit is set. Bus free time between stop condition and start condition tbus 1 µs Page 5/6

6 MR (Measurement Requests) By a measurement request command, the sleep mode is terminated and the humidity module executes a mesurement cycle. The measuring cycle begins with the temperature measurment, followed by humidity measurement, digital signal processing (linearizing, temperature compensation) and finally writing the processed measured values into the output register. The MR command consists of the adress of the humidity module, with which the R/W bit is transferred as 0(= write). After the hymidity module is answered with ACK (= mesurement started), the master finalized the transfer with NACK (=stop condition). DF (Data Fetch) The data fetch command serves to finish reading the output register. The DF command is sent by the master to the Humidity module (Slave) and begins with the 7 Bit slave 8. bit as 1 (= read). The Humidity module sends back an acknowledgement (ACK) in case of incorrect addressing The number of bits, that the humidity module sends back, is distiguished when the master sends a NACK (= stop condition). The first two bytes of measurement data contain the two status bits as MSB, then followed by the humidity value with 14 bits. If the temperature data is also needed, then these can be read after the humidity value. The most significant 8 bits of the temperature value will be transferred as third byte. Then the least significant 6 bits of the temperature value can be read as the fourth byte. The last two bits are not used and should be masked away. The master has the possibility to terminate the reading after each read byte through an NACK. Hence, it is possible to finish reading even after the first byte and evaluate only the status/stale bit and the master can terminate the transfer without completing the whole cycle. If only the upper 8-bits of the temperature value are to be transferred (8 bit resolution), the transfer can be aborted after the third byte by a NACK. Page 6/6