BQ27542EVM: Bus free time between stop and start

Statham Su

Genius 4990 points

Part Number: BQ27542EVM

Hello Sir:

We have a question on I2C bus free time.

We checked datasheet that tBUF was 66us.

But our tested result that tBUF is around 28us.

It's not meet datasheet.

Is it normal?

Please kindly give us some explanation.

Looking forward your feedback.

Thanks a lot.

over 1 year ago

0 Statham Su over 1 year ago

Genius 4990 points

Hello Sir:

Updated our tested result.

0 Adrian over 1 year ago in reply to Statham Su

TI__Mastermind 37761 points

Hey Statham,

No that is not normal. You will need to change your timing on the host to match the datasheet to at least the minimum value. You will need to add more buffer time between communication so the gauge is able to have enough time to process incoming communication.

Regards,

Nick Richards

0 TsungMin Tsai over 1 year ago in reply to Adrian

Prodigy 50 points

Hi Nick,

Good day.

Sorry to bother you.

I want to inquire about waveforms with you.

1.
Is the TBuf time reasonable?
I checked other products utilizing I2C and found that the TBuf does not exceed 10us.
At least 66 us is necessary for the TI GAUGE IC. I'm unsure if this is reasonable?

2.
It appears to me that the clock frequency of the waveform being discussed is estimated to be 100kHz.
Does the clock have an impact on TBuf time?

Is 66us(TBuf) defined as a clock frequency of 400kHz?
So is 28us reasonable at 100kHz?

Thank you for being patient with me.

TsungMin Tsai

0 Adrian over 1 year ago in reply to TsungMin Tsai

TI__Mastermind 37761 points

Hey TsungMin,

1. This is what the design engineers choice for TBuf time. I can not speak on whether that value is reasonable or not. I would assume that this value is a safe value to ensure communication is sent without errors.

2. The TBuf time is independent of clock frequency

Regards,

Nick Richards

0 TsungMin Tsai over 1 year ago in reply to Adrian

Prodigy 50 points

Hi Nick,

Thank you for your reply.
I understand, thank you very much.

Best regards.

TsungMin Tsai

0 Adrian over 1 year ago in reply to TsungMin Tsai

TI__Mastermind 37761 points

Hey TsungMin,

Your welcome, Glad I was able to help.

Regards,

Nick Richards

Power management

Power management forum

BQ27542EVM: Bus free time between stop and start