LP8866-Q1: I2C doesn't response ACK

Jerry Chen

Part Number: LP8866-Q1

Hi team,

In below design, we found the Bit 9/ACK is always high. We checked the schematics, changed Pin 33/MODE resistor to 11kohm/1%, and demounted other devices on the same I2C bus. LP8866 still doesn't response ACK. Is there anything else that I could try?

Thanks.

Below is the same I2C write to EVM. You could see the ACK bit is pulled low.

over 4 years ago

0 Frank Qiu over 4 years ago

TI__Genius 15776 points

Hi Charles, could you help in this case?

0 Charles-Chen over 4 years ago

TI__Genius 11836 points

Hi Jerry,

I don't see the enable signal of device. Please also check the power supply of device. Try to use the customers' MCU to communicate with the EVM board to verify to correctness of software. In the figure1, please also zoom the waveform and provide the signal of EN with the corresponding resistor value of mode pin.

0 Jerry Chen over 4 years ago in reply to Charles-Chen

TI__Expert 5110 points

Hi Charles,

I would like to add more information. The analog functions are good. We can drive the LEDs by analog dimming. The only issue is I2C communication.

0 Charles-Chen over 4 years ago in reply to Jerry Chen

TI__Genius 11836 points

Hi Jerry,

Please check other suggestions.

0 Jerry Chen over 4 years ago in reply to Charles-Chen

TI__Expert 5110 points

Hi Charles,

Pin 1 VDD is measured as 3.3V. Pin 2 EN is measured as 3.3V. Customers' MCU can communicate with the EVM board correctly. R_BST_FSET=7.87kohm, R_PWM_FSET=3.88k, R_LED_SET=5.62k, R_ISET=15.86kohm. Below is the zoom in of SCA & SCLK signal. Bit 9 for ACK is always 1'b1 in the customer board. We are checking of EN is still enabled during I2C communication.

Do you see anything wrong?

Thanks.

0 Charles-Chen over 4 years ago in reply to Jerry Chen

TI__Genius 11836 points

Hi Jerry,

What's the value of resistor of mode pin when the customer measure this waveform? I see the mode resistor is 121k and is different from 11k in the EVM board. Please also provide the EN, SCL, SDA, VCC in the same waveform.

0 Jerry Chen over 4 years ago in reply to Charles-Chen

TI__Expert 5110 points

Hi Charles,

As I described in the original question, Mode pin resistor has been changed to the EVM's 11kohm. Below is the SCL SDA and EN waveform. We will add VCC tomorrow.