BQ25756: BQ25756 delay to start reverse mode

Francesco Paparella

Part Number: BQ25756

Tool/software:

Hello,

We are facing a considerable delay (250 ms) for the BQ25756 charger to start the reverse mode when the system voltage Vsys is dropped. The charger is set in reverse mode by setting the bit EN_REV = 1 before the Vsys is dropped. Any idea on how to reduce this delay?

Thanks

Francesco Paparella

2 months ago

0 Michael Bradbourne 2 months ago

TI__Expert 6025 points

Hi Francesco,

The Vsys, do you mean the voltage on VAC? This voltage must be below VAC_UV before EN_REV can be set. Is this the case when you set EN_REV=1?

Best,
Michael

0 Francesco Paparella 2 months ago in reply to Michael Bradbourne

Prodigy 60 points

Yes, I meant Vac.

We have a detection signal (yellow line below) that indicates that our Vac voltage (blue line) is dropping 50V->0V. After the detection signal goes high, the I2C command 0x19 with EN_REV =1 is sent. As you can see below, the Vac voltage goes up again to 40V (BQ25756 chip goes in discharge mode) only after 400 ms.

Can you tell us the cause of this delay?

thanks

0 Michael Bradbourne 2 months ago in reply to Francesco Paparella

TI__Expert 6025 points

Hi Francesco,

What are the values of the VAC_UV/VAC_OV resistor divider?
What is the value of REG0x08_Input_Voltage_DPM_Limit?

Best,
Michael

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BQ25756: BQ25756 delay to start reverse mode