This module has a 4-Channel 5v / 3.3v logic conversion that converts the 5v communication to 3v bidirectional a bridge of communication between 3v logic and 5v logic device, and it has four MOSFET to stabilize four channel, Stabilize the UART, IIC, SPI and two way transformation
Schematics Diagram
This module works well in Arduino that communicate with your sensor via I2C protocol very helpful to stabilize the communication between your sensor and the MCU.
Download the datasheet here | BSS138 N-CHannel
Download the eagle file here | Eagle File