TPS55288: I2C Communication being lost on other Peripherals when TPS55288 Output Enabled.

Liam Sullivan

Part Number: TPS55288

Tool/software:

Hello,

I am having some issues with the TPS55288 causing the i2c bus it is on to go unresponsive for other peripherals on the bus when the TPS55288's output is enabled.

Currently the TPS55288 is only setting the REF register through I2C to be 0x0106 to set the voltage output to be 6V with all other registers staying at their default configuration. The switching frequency is set to 396.8kHz with Rfsw being 50kOhm.

When output is enabled through the OE bit in the MODE register is when issues arise. My separate peripherals with addresses 0x76 and 0x77 are then unable to communicate via I2C and all transactions are giving NACKs, during this time. Communication can be facilitated between the MCU and the TPS55288 and one other separate peripheral (I2C address: 0x23) on the same I2C however.

Since these issues only arise when the output is enabled for the TPS55288 it seems to be an issue with this IC, I am able to resolve the issue by turning the output off then back on when a i2c transaction is taking place but would like to be able to keep the voltage output enabled during this time.

I have also attached the schematic of the power supply design.

Any help would be greatly appreciated!

8 months ago

0 Mulin Yuan 8 months ago

TI__Genius 15180 points

Hi Liam,

Thank you for reaching out. May I know what is the application here?

TPS55288 is a slave device and it will not influence other device. You can check the SCL and SDA waveforms when you communicate with the 76h/77h device with 55288 enabled/disabled. Check if there is any difference between the waveform.

Regards,

Mulin

0 Liam Sullivan 8 months ago in reply to Mulin Yuan

Prodigy 20 points

Hi Mulin,

The application for this is to supply power from the voltage output through a trace to heat it up and control the short to ground via a MOSFET gate that is being PWM'd. The device I am trying to read from and having issues with the I2C is a temperature sensor to get the temperature of the surrounding area of the trace.

Here are some waveforms I was able to capture.
TPS55288 Disabled:

TPS55288 Enabled:

As can be seen, once the device is enabled we are no longer able to get a proper response from the temperature sensor. Currently for the layout, the temperature sensor is directly below the trace that is being heated and powered from the TPS55288 as seen here.

Our current theory is that the switching frequency of the supply could be possibly effecting the internals of the temperature sensor due to possible EMI and the switching frequency being within the i2c frequency of 100kHz to 400kHz. Hence, the other question I asked and you answered about changing the switching frequency, however when we did this the high side FET was broken.