Problems with the MP3302DJ

chenbingjy

Problems with the MP3302DJ [Copy link]

The circuit uses LCD backlight driver chip MM3302DJ, 5V power supply, LCD_BL has a wire flying. EN3.18V, but FB voltage does not have 200mV output. What's going on? Thank you!

chenbingjy

BL_VCC4.6V. If the screen is not connected, the 200mV will be gone? I tested the screen on the development board, took it off, and there was no 200mV when it was powered on, but there was when it was connected

xiaxingxing

"Feedback Input. The MP3302 regulates the voltage across the current sense resistor between FB and GND. Connect a current sense resistor from the bottom of the LED string to GND. Connect the bottom of the LED string to FB. The regulation voltage is 200mV." You need to connect the backlight to form a loop, and the LED current will flow through the sense resistor, which is R19 in your figure, so that a voltage of 200mV will appear at the FB port. In addition, whether the voltage of your EN port meets the requirements, read the datasheet carefully, the voltage of the FB port is also related to the voltage of EN.

chenbingjy

xiaxingxing 发表于 2018-10-13 18:14
"Feedback Input. The MP3302 regulates the voltage across the current sense resistor between FB and G ...

谢谢！