TPS659037: Communication problem

Tadahiko-san,

Hi, can you provide scope shots of the I2C lines during this first write? Also can you tell us which what the pullup resistors on the I2C lines are powered by?

Thanks,

Nastasha

Nastasha-san,

Thank you for your reply.

I attaches the waveforms.

TPS659037 Start up.xlsx

I2C lines should be pulled up by external(not TPS659037) power supply.

I'll check it.

Best Regards,

Kuramochi

Kuramochi-san,

Thanks for sharing the scope shots. I recommend checking the power supply on the pullup resistors and also making sure that the pullup resistors are a good size (2.4K or 4.7K should be okay).

Thanks,

Nastasha

Hi Natasha-san,

As I mentioned above, this symptom is not caused by external circuit because SCL line is pulled up by removing TPS659037.

What case is TPS659037 pulls down SCL line?

I think that this device doesn't pull down it normally.

Best Regards,

Kuramochi

Hi

How is this progress?

Best Regards,

Kuramochi

Kuramochi,

I went ahead and checked with my design colleagues to get more insight on possible causes. We don't have any known behavior in the TPS659037 that keeps the PMIC SCL low. It is more likely the master I2C device or other device on the bus causing this behavior every once in a while. One way to check is to add a series resistor (around 100 ohms) on the SCL line and measure the ground levels to see if they are different.

Thanks,

Nastasha

Hi Nastasha-san,

Thank you for your reply.

Did you mean that there is no trigger to enter this mode which keeps the PMIC SCL low?

If you know any factor to change the I2C behavior, please let me know.

And, we will ask our customer to add a series resistor on the SCL line.

Best Regards,

Kuramochi