SPECIFICATIONS

1. AHT21B- Temperature and Humidity sensor:

• Complete calibration

• Digital output, I²C interface

• P2C interface

• Excellent long-term stability

• Quick response

• Strong anti-interference ability

• A variety of accessories are available for customized applications

AHT21B Digital Temperature and humidity module is a temperature and humidity composite sensor with calibrated digital signal output. It uses special digital module acquisition technology and temperature and humidity sensing technology to ensure that the product has very high reliability and excellent long-term stability. The product has the advantages of excellent quality, rapid response, strong anti-interference ability and high cost performance. Each sensor is calibrated in a professional humidity check room to achieve higher accuracy standards. The standard l2C interface makes the system integration easy and fast. Its small size and low power consumption make it the best choice for all kinds of applications, even the most demanding.

2. Application scenario:

Hvac, dehumidifier, test and detection equipment, consumer goods, automobiles, automatic control, data recorder, weather station, home appliances, humidity regulation, medical and other related temperature and humidity detection and control.

3. Product parameters:

4. Sensor performance：

5. Interface definition:

1. VCC: power supply voltage

2. SDA: serial data, two-way port

3. GND: ground

4. SCL: serial data, two-way port

Power pin (VDD,GND)

The power supply range of AHT21B is 2.0-5.5V, the recommended voltage is 3.3V, and the decoupling capacitor 100NF must be added between VCC and GND to act as a filter.

Serial clock SCL

SCL is used for communication synchronization between microprocessor and AHT21B. Because the interface contains completely static logic, there is no minimum SCL frequency.

Serial data SDA

SDA pins are used for data input and output of the sensor. SDA is effective on the rising edge of the serial clock SCL when the command is sent to the sensor, and SDA must remain stable when the SCL is at high level. After the falling edge of SCL, the SDA value can be changed. To ensure communication security, the effective time of SDA should be extended to TSU AND THO before the rising edge of SCL and after the falling edge of SCL, respectively. When reading data from the sensor, SDA is effective after the SCL becomes low (TV) and remains effective until the falling edge of the next SCL.

6. Typical application circuit：

To avoid signal collisions, microprocessors (MCU) must only drive SDA and SCL at low levels. An external pull-up resistor (e.g. 4.7~10KO) is required to pull the signal to high levels. Pull-up resistors may usually be included in the microprocessor's I/○ circuit.

7. Note:

• The pull-up voltage of SDA must be supplied by VCC, and the supply voltage range is 2.0~5.5V;

• The capacity between VCC and GND should be 100NF decoupling capacitor;

• AHT21B can share PC bus with other l2C devices.

8. Product picture: