BQ24272, is there any issue with the I2C interface?

We are not aware of an issue.  Are you using TI's bq24272EVM and EVM software?

No. The master is an Atmel atmega32. Also some times the bq24272 did not acknowledge at all. I have not similar issues with other slave devices. Pull up resistor at 3V for SDA and SCK is ok?

3V pullup is okay.  Are the rise times of the pulses within I2C spec?

The rise time its OK. I use low baud rate (100KHz) and I tried small pull up resistors (1K). The problem appears more often when the charger is running.

Hello,

I tested a BQ24272 EVM during charging and monitored the SCL and SDA lines with the scope. For my testing I shortened the watchdog reset to once a second to try to catch any issues that might be evident in the I2C communication.

Below is a sample of the waveforms that I observed consistently during charging. The top is a 50us and the bottom is 20us.

I did not observe any issues with the communication or any observed interruptions in the charging.

I do see that the problematic transaction you have captured bears a strong resemblance to the second half of the sampled communication. However there was no fault in the communication observed in my testing. However the baud rate of the EVM & USB interface is lower to 100kbaud.

Have you tested at a lower baud rate? Do you still see communications issues?

Thank you for your time Ryan!

I change the capacitor of BYPASS PIN (pin 23) to 1uF from 0.1uF that a had in the first place. The datasheet recommend 0.1uF minimum capacitance. The things are better now. I still testing it. I will try lower baud rate, too. I will keep you informed.

In fact, in my case, the larger capacitor improve the i2c communication. Now the issues appears more seldom. Do you think the reason may be poor grounding? In my prototype I have not solder the thermal pad to ground because I have soldered the IC by hand.

Another issue a discovered is that some times the charge is not terminated. The TE is enabled and the termination current is set to 400mA. The consumption of the rest components  is 40mA.

In low charge mode is the "charge current termination" disabled?

Hello Anastasios,

The larger bypass capacitor should attenuate any higher frequency noise better which makes the improvement in the I2C understandable.

The disconnected thermal pad is something that needs to be fixed with the datasheet explicitly stating it should be connected directly to a ground potential. Are you able to solder the pad?

When the device does not terminate does the current simply continue to taper lower and lower?

Are you only seeing this failure to terminate when the LOW_CHG bit is enabled?

Hello,

I order a stencil and I will solder the BQ24272 properly. I believe the issue with the I2C is due to unsoldering thermal pad. Don't you believe? The lower baud rate didn't help the I2C.

When the device does not terminate, the current continues to lower near zero mA. When the safe timer expires the charging terminates and  'Battery OVP' fault return. This happen when LOW_CHG bit is enabled. Until now I haven't noticed it when the LOW_CHG bit is disabled.

Thank you

Hello Anastasios,

When the LOW_CHG bit is enabled the safety is slowed and the termination is disabled. This is why you are not seeing seeing termination in when that bit is set.

There is no known issue with the I2C protocol.