TPS65400: Questions about I2C + ALERT PINs

Denis Alain1

Part Number: TPS65400

Hi,

We would like to use the TPS65400 within a new product because we want to control power sequencing by programming the internal EEPROM of the DC_DC in prod. Do we need to use the I2CALERT pin to do that?

The pull-up resistors of the I2C bus will be powered by the DC-DC output #4, since the MCU is powered by this DC-DC's output. Is-it a problem, since the I2C pull-up won't be powered until the DC_DC's output #4 turns ON?

Thanks,
Denis Alain, Eng.

over 5 years ago

0 Zhao Ma over 5 years ago

TI__Genius 15135 points

Hi, Denis

1. No need to use the I2CALERT pin when programming the internal EEPROM.

There is programming guidance for reference.

TPS65400_Programming_Guidance.zip

2. You can make I2C pull-up by VDDD pin, see the EVM schematic.

https://www.ti.com/lit/ug/slvuac4/slvuac4.pdf?ts=1594971695125&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS65400%253FkeyMatch%253DTPS65400%2526tisearch%253DSearch-EN-everything%2526usecase%253DGPN

0 Denis Alain1 over 5 years ago in reply to Zhao Ma

Intellectual 600 points

Thanks Zhao. We will look at this document for programming.

If I use VDDD to pull-up I2C buses, the I2C pins on the MCU will be powered before the MCU IOs bank and I will violate the IOs spec of the MCU itself. The only way I know to do that is by using an I2C buffer (repeater) that can support unpowered I2C bus on one side. I wanted to avoid this extra component, but I think it will be necessary.

Best Regards,

Denis Alain, Eng.

0 Zhao Ma over 5 years ago in reply to Denis Alain1

TI__Genius 15135 points

Hi, Denis

I understand your application.

Back to your initial question:

"The pull-up resistors of the I2C bus will be powered by the DC-DC output #4, since the MCU is powered by this DC-DC's output. Is-it a problem, since the I2C pull-up won't be powered until the DC_DC's output #4 turns ON?"

You are worrying that "I2C pull-up won't be powered" will affect TPS65400 work?

I think it is not problem, the TPS65400 will startup according to the setting value in EEPROM.

0 Denis Alain1 over 5 years ago in reply to Zhao Ma

Intellectual 600 points

Thanks Zhao,

You understand my concern about the pull-ups. So I will connect them directly to my MCU.

Best Regards,

Denis Alain, Eng.

Power management

Power management forum

TPS65400: Questions about I2C + ALERT PINs