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Version:V1.0 —— May 2021

AHT20 Data Sheet

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5 Interface Definition

Table 5. Sensor pin distribution (top view)

5.1 Power Pin (VDD, GND)

The power supply range of the sensor is 2.2-5.5V. A decoupling capacitor of 10uF must be added between VDD

and GND to play a filtering role. VDD is better than SDA and SCL power on or synchronous power on, to avoid the

signal line (SCL/SDA) leakage current into the chip, resulting in power on the chip in the non-working state.

5.2 Serial Clock SCL

The serial clock is used to synchronize the communication between the microprocessor and sensor. Since the

interface contains completely static logic, there is no minimum SCL frequency.

5.3 Serial Data SDA

SDA pins are used for data input and output of the sensor. The SDA is effective on the rising edge of the serial

clock SCL when sending commands to the sensor, and the SDA must remain stable when the SCL is at high levels.

After the SCL falling edge, 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 - refer

to Figure 17.When reading data from the sensor, the SDA is effective after the SCL is low (TV) and remains until

the falling edge of the next SCL.

Figure 16. Typical application circuit

Note:

1. The pull-up voltage of SCL and SDA must be powered by VDD, and the power supply voltage range is 2.2~ 5.5V;

2. Add 10μF decoupling capacitor between VDD and GND

3. In order to ensure that the sensor is not disturbed by the circuit, please add filter circuit to the VDD, such as R1 and C1 on

the typical circuit.

To avoid conflict of signal, the microprocessor (MCU) must be driven SDA and SCL only at low level, need an

external pull-up resistors (for example: 2.0 ~ 4.7 K Ω) will lift the signals to high level, pull-up resistance may have

often included in a microprocessor I/O circuits. Refer to Tables 7 and 8 for detailed information on sensor

input/output characteristics.