Datasheet SHT20 (Sensirion) - 7
| Manufacturer | Sensirion |
| Description | ±3% Digital humidity and temperature sensor |
| Pages / Page | 14 / 7 — 5.1 Start Up Sensor. SCL. SDA. 5.2 Start / Stop Sequence. Figure 12. … |
| File Format / Size | PDF / 478 Kb |
| Document Language | English |
5.1 Start Up Sensor. SCL. SDA. 5.2 Start / Stop Sequence. Figure 12. Figure 13. Table 5. Figure 14. Communication with Sensor
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5.1 Start Up Sensor
1/fSCL t t As a first step, the sensor is powered up to the chosen SCLH tSCLL R tF supply voltage VDD (between 2.1 V and 3.6 V). After 70%
SCL
power-up, the sensor needs at most 15 ms, while SCL is 30% high, for reaching idle state, i.e., to be ready accepting t SDA valid write commands from the master (MCU). Current consumption SU tHD during start up is 350 µA maximum. Whenever the sensor DATA IN 70% is powered up, but not performing a measurement or
SDA
communicating, it is automatically in idle state (sleep 30% mode). SDA valid read tR tVD tF
5.2 Start / Stop Sequence
DATA OUT 70% Each transmission sequence begins with Start condition
SDA
30% (S) and ends with Stop condition (P) as displayed in Figure
Figure 12
Timing Diagram for Digital Input/Output Pads, 13 and Figure 14. abbreviations are explained in Table 5. SDA directions are seen 70% from the sensor. Bold SDA line is controlled by the sensor, plain
SCL
SDA line is controlled by the micro-controller. Note that SDA 30% valid read time is triggered by falling edge of anterior toggle. 70%
SDA
Parameter min typ max Units 30% SCL frequency, fSCL 0 - 0.4 MHz
Figure 13
Transmission Start condition (S) - a high to low SCL High Time, tSCLH 0.6 - - µs transition on the SDA line while SCL is high. The Start condition SCL Low Time, t is a unique state on the bus created by the master, indicating to SCLL 1.3 - - µs the slaves the beginning of a transmission sequence (bus is SDA Set-Up Time, tSU 100 - - ns considered busy after a Start). SDA Hold Time, tHD 0 - 900 ns SDA Valid Time, tVD 0 - 400 ns 70%
SCL
SCL/SDA Fall Time, tF 0 - 100 ns 30% SCL/SDA Rise Time, tR 0 - 300 ns Capacitive Load on Bus Line, CB 0 - 400 pF 70%
SDA Table 5
Timing specifications of digital input/output pads for I2C 30% fast mode. Entities are displayed in Figure 12. VDD = 2.1 V to
Figure 14
Transmission Stop condition (P) - a low to high 3.6 V, T = -40°C to 125°C, unless otherwise noted. transition on the SDA line while SCL is high. The Stop condition is a unique state on the bus created by the master, indicating to
5
the slaves the end of a transmission sequence (bus is
Communication with Sensor
considered free after a Stop). SHT20 communicates with I2C protocol. For information on I2C beyond the information in the following Sections
5.3 Sending a Command
please look for the NXP I2C-bus specifications and user After sending the Start condition, the subsequent I2C manual. header consists of the 7-bit I2C device address ‘1000’000’ Please note that all sensors are set to the same I2C and an SDA direction bit (Read R: ‘1’, Write W: ‘0’). The address, as defined in Section 5.3. sensor indicates the proper reception of a byte by pulling the SDA pin low (ACK bit) after the falling edge of the 8th Furthermore, please note, that Sensirion provides an SCL clock. After the issue of a measurement command exemplary sample code on its home page – compare (‘1110’0011’ for temperature, ‘1110’0101’ for relative www.sensirion.com/products/catalog/SHT20/. humidity’), the MCU must wait for the measurement to Please note that in case VDD is set to 0 V (GND), e.g. in complete. The basic commands are summarized in Table case of a power off of the SHT2x, the SCL and SDA pads 6 below. are also pulled to GND. Consequently, the I2C bus is blocked while VDD of the SHT2x is set to 0 V. www.sensirion.com Version 5 – October 2022 7/14
5.1 Start Up Sensor
1/fSCL t t As a first step, the sensor is powered up to the chosen SCLH tSCLL R tF supply voltage VDD (between 2.1 V and 3.6 V). After 70%
SCL
power-up, the sensor needs at most 15 ms, while SCL is 30% high, for reaching idle state, i.e., to be ready accepting t SDA valid write commands from the master (MCU). Current consumption SU tHD during start up is 350 µA maximum. Whenever the sensor DATA IN 70% is powered up, but not performing a measurement or
SDA
communicating, it is automatically in idle state (sleep 30% mode). SDA valid read tR tVD tF
5.2 Start / Stop Sequence
DATA OUT 70% Each transmission sequence begins with Start condition
SDA
30% (S) and ends with Stop condition (P) as displayed in Figure
Figure 12
Timing Diagram for Digital Input/Output Pads, 13 and Figure 14. abbreviations are explained in Table 5. SDA directions are seen 70% from the sensor. Bold SDA line is controlled by the sensor, plain
SCL
SDA line is controlled by the micro-controller. Note that SDA 30% valid read time is triggered by falling edge of anterior toggle. 70%
SDA
Parameter min typ max Units 30% SCL frequency, fSCL 0 - 0.4 MHz
Figure 13
Transmission Start condition (S) - a high to low SCL High Time, tSCLH 0.6 - - µs transition on the SDA line while SCL is high. The Start condition SCL Low Time, t is a unique state on the bus created by the master, indicating to SCLL 1.3 - - µs the slaves the beginning of a transmission sequence (bus is SDA Set-Up Time, tSU 100 - - ns considered busy after a Start). SDA Hold Time, tHD 0 - 900 ns SDA Valid Time, tVD 0 - 400 ns 70%
SCL
SCL/SDA Fall Time, tF 0 - 100 ns 30% SCL/SDA Rise Time, tR 0 - 300 ns Capacitive Load on Bus Line, CB 0 - 400 pF 70%
SDA Table 5
Timing specifications of digital input/output pads for I2C 30% fast mode. Entities are displayed in Figure 12. VDD = 2.1 V to
Figure 14
Transmission Stop condition (P) - a low to high 3.6 V, T = -40°C to 125°C, unless otherwise noted. transition on the SDA line while SCL is high. The Stop condition is a unique state on the bus created by the master, indicating to
5
the slaves the end of a transmission sequence (bus is
Communication with Sensor
considered free after a Stop). SHT20 communicates with I2C protocol. For information on I2C beyond the information in the following Sections
5.3 Sending a Command
please look for the NXP I2C-bus specifications and user After sending the Start condition, the subsequent I2C manual. header consists of the 7-bit I2C device address ‘1000’000’ Please note that all sensors are set to the same I2C and an SDA direction bit (Read R: ‘1’, Write W: ‘0’). The address, as defined in Section 5.3. sensor indicates the proper reception of a byte by pulling the SDA pin low (ACK bit) after the falling edge of the 8th Furthermore, please note, that Sensirion provides an SCL clock. After the issue of a measurement command exemplary sample code on its home page – compare (‘1110’0011’ for temperature, ‘1110’0101’ for relative www.sensirion.com/products/catalog/SHT20/. humidity’), the MCU must wait for the measurement to Please note that in case VDD is set to 0 V (GND), e.g. in complete. The basic commands are summarized in Table case of a power off of the SHT2x, the SCL and SDA pads 6 below. are also pulled to GND. Consequently, the I2C bus is blocked while VDD of the SHT2x is set to 0 V. www.sensirion.com Version 5 – October 2022 7/14