BQ2022A: BQ2022A Power-on waveform

Wei-Hao Chen (TW-FAE)

Part Number: BQ2022A

Hi Support Team:

My customer is having a issue during the power-up of BQ2022A device, they found the SDQ signal has been pull-down twice. This is caused by the host MCU or the standard startup sequence for BQ2022A?

VCC = 3.3V
Slew rate: 2.5V/1ms
First low pulse duration: 80us
Second low pulse duration: 120us
Duration between low pulses: 40us

Thank you.

Best Regards,

Wei-Hao

over 7 years ago

0 Kang Kang over 7 years ago

TI__Mastermind 24870 points

Hello Wei-Hao,

Can you try the same initialization procedure using a TI EV2300 and measure the waveform. If you do not see this pattern, I would believe it is the host pulling the line low.

Thanks!

0 Wei-Hao Chen (TW-FAE) over 7 years ago in reply to Kang Kang

TI__Expert 3260 points

Hi Kang,

I do not have the EV2300 and BQ2022A EVM on my hands, could you please verify this for us?

Thank you.

Best Regards,
Wei-Hao

0 Wei-Hao Chen (TW-FAE) over 7 years ago in reply to Kang Kang

TI__Expert 3260 points

Hi Kang,

Our customer has verified the SDQ was pulling down by the BQ2022A, by connecting the SDQ with a 2kohm pull-up resistor to a DC source (without any host):

And they found with different slew rate of the DC supply, the BQ2022A behaves differently. Could you please explain why? and why does SDQ being pulled-low during the start-up phase?

VPU Slew rate = 2.0V/ms