1、附录 三 外文翻译 外文资料 SHT1x / SHT7x Humidity & Temperature Sensor - 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 - S
2、mall 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 reliabil
3、ity 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
4、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 coeff
5、icients 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 application
6、s.The device is supplied in eith surface-mountable LCC (Leadless Chip Carrier) or as a pluggable 4-pin single-in-line type package. Customer specific packaging options may beavailable on request. Applications _ HVAC _ Automotive _ Consumer Goods _ Weather Stations _ Humidifiers _ Dehumidifiers _ Tes
7、t & Measurement _ Data Logging _ Automation _ White Goods _ Medical 2 Interface Specifications Figure 2 Typical application circuit 2.1 Power Pins The SHTxx requires a voltage supply between 2.4 and 5.5 V. After powerup the device needs 11ms to reach its “sleep” state. No commands should be sent bef
8、ore that time.Power supply pins (VDD, GND) may be decoupled with a 100 nF capacitor. 2.2 Serial Interface (Bidirectional 2-wire) The serial interface of the SHTxx is optimized for sensor readout and power consumption and is not compatible with I2C interfaces, see FAQ for details. 2.2.1 Serial clock
9、input (SCK) The SCK is used to synchronize the communication between a microcontroller and the SHTxx. Since the interface consists of fully static logic there is no minimum SCK frequency. 2.2.2 Serial data (DATA) The DATA tristate pin is used to transfer data in and out of the device. DATA changes a
10、fter the falling edge and is valid on the rising edge of the serial clock SCK. Duringtransmission the DATA line must remain stable while SCK is high. To avoid signal contention the microcontroller should only drive DATA low. An external pull-up resistor (e.g. 10 k ) is required to pull the signal hi
11、gh. (See Figure 2) Pull-up resistors are often included in I/O circuits of microcontrollers. See Table 5 for detailed IO characteristics. 2.2.3 Sending a command To initiate a transmission, a “Transmission Start” sequence has to be issued. It consists of a lowering of the DATA line while SCK is high
12、, followed by a low pulse on SCK and raising DATA again while SCK is still high. Figure 3 Transmission Start sequence The subsequent command consists of three address bits (only “000” is currently supported) and five command bits. The SHTxx indicates the proper reception of a command by pulling the
13、DATA pin low (ACK bit) after the falling edge of the 8th SCK clock. The DATA line is released (and goes high) after the falling edge of the 9th SCK clock. 2.2.4 Measurement sequence (RH and T) After issuing a measurement command (00000101 for RH, 00000011 for Temperature) the controller has to wait
14、for the measurement to complete. This takes approximately 11/55/210 ms for a 8/12/14bit measurement. The exact time varies by up to 15% with the speed of the internal oscillator. To signal the completion of a measurement, the SHTxx pulls down the data line and enters idle mode. The controller must w
15、ait for this “data ready” signal before restarting SCK to readout the data. Measurement data is stored until readout, therefore the controller can continue with other tasks and readout as convenient. Two bytes of measurement data and one byte of CRC checksum will then be transmitted. The uC must acknowledge each byte by pulling the DATA line low. All values are MSB first, right justified. (e.g. the 5th SCK is MSB for a 12bit value, for a
