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Question asked by Marius Häffner on Jan 8, 2019
Latest reply on Jan 10, 2019 by G.w. Sun



I have a problem with NXP´s LED driver pca9634 and its I2C communication. (datasheet).


For setup and programming I followed the instructions of the datasheet.



  • i2c master µC: ATMEGA32U4 (datasheet).
  • The PCA9634 is the only bus slave so i chose the address 0x01 (A0=HIGH and A1..A6 connected to gnd).
  • bus speed: 100kHz
  • pull up resistors: 4k7 (Vdd = 5V)
  • LED resistors 430 ohms / I = 11mA


The schematic is attached.



The PCA9634 works fine for a while (about 10 minutes) then it stucks at the current state (blinking, permanent on/off).

Analyzing the signals with an oscilloscope shows:

  • SDA = 5V
  • SCL = 1V constant.

After power off/on reset the chip does not work anymore at all!


Furthermore I used another µC as master (SAMat03463 --> datasheet) and in a third scenario an i2c-USB emulator.

I always have the same result as described.



Does anybody has an advice for this issue or had a similar behavior?


I`m very grateful for every response.


Best regards,