BQ25710: BQ25710 With the battery unconnected, the AC adapter is used to power the system via VSYS.

Hi Star,

BQ25710 should support adapter power only (no battery) and should regulate VSYS to VMinSys.

Can you provide some more details about how to reproduce this issue? Is this on EVM or on a customer design?

Thanks,

Khalid

Hi Khalid

Thanks for your reply.

The customer design the schematic with BQ25710 and find the following issue.

1, If the battery and adapter are connected at the same time, VBUS can support 7-22V and work normally, the battery is 3 series.

If only the adapter is connected, and the VBUS voltage is lower than 16V, BQ25710 will report sys_ Short fault, CHRG_ OK is low, Vsys is 1.5V.

2. Form the datasheet we know the CELL_BATPRESZ pin is pulled below VCELL_BATPRESZ_FALL to indicate battery removal. But when I pull down the  CELL_BATPRESZ pin, it will report sys_ Short fault. 

Please give some suggestions about this problem.

Thanks

Star

Hello Star,

SYS_SHORT fault means that the system voltage has dropped below 2.4V. The device should regulate System voltage above this value whether a battery is attached or not. Since the issue is happening at certain VBUS condition (<16V) please check the input supply clamp and input capacitance. Is there a load on the System?

Khalid

Hi Khalid 

Thanks for your reply.

1. During the test, the system load and no load conditions are the same, and the SYS_SHORT fault is reported when the Vbus is lower than 16V;

2.Please help check the schematic as below.

PWR_IN_JM.pdf

Waiting for your reply.

Thanks

Star

Hello Star,

The schematic has a a lot of circuitry on the input side, have you isolated the charger chip by applying voltage directly at VBUS?

One thing I noticed, VSYS pin is connected through a FET to the System, we recommend connecting directly with Kelvin connection as it is important that the device senses the SYS voltage accurately. There are a number of signals that can open this FET, and it's possible this is the reason the device detects a SYS_SHORT. Can you please check the voltage of the System at the SYS_PWR point as well as at the BQ25710 SYS pin, and check whether this FET is open or closed?

Thanks,

Khalid

Hi Khalid

Thanks for your help.

The problem has been resolved after changing the R595 to 0Ω.

Still have some query need your help.

1,Will affecting the stable operation when change the value of R595 to 0 Ω? Because the reference design value is 1 Ω.

2, If the battery is removed during normal operation, Does CELL_ BATPRESZ pin need to pull low?

3, Does BQ25710 support battery hot plug？

Waiting for your reply.

Thanks

Star