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BQ25898D: Charging current higher than set value.

Part Number: BQ25898D
Other Parts Discussed in Thread: BQ25890

Hi guys,

I have met a problem while using BQ25898D, we set the fast charging current to 1024mA, but sometimes the charging current is 1.3A ( I think with higher ILIM, this value will increase) .

This is likely to happen when the battery voltage is low, about 3.2V. 

And if I set the VSYSMIN to 3.0V (In our original design it is default value, 3.5V) , it won't happen.  It seems this issue is related to NVDC feature.

This issue is also found on EVM, you can try to reproduce in you lab. 

Below is the application information. 

  • Product:battery charger, besides the battery no circuit is to be powered by the charger .
  •  Input voltage: 12V
  • Test condition: room temperature;
  • The register setting: 

0x48, //reg00
0x01, //reg01
0x1D, //reg02
0x1A, //reg03:
0x10, //reg04:ich=1024mA
0x11, //reg05:iterm=128mA
0x5E, //reg06:
0x8D, //reg07:disable watchdog
0x4F, //reg08:40mohm,96mV
0x54, //reg09:JEITA_VSET=1

Other registers are default values. 

  • The schematic. 

My questions are:

1) Could you please confirm this issue?

2) Could you please explain the root cause for this issue?

3) Is there any side effect if we change VSYSMIN from .3.5V to 3.0V? There is no circuits to be supplied by the VSYS in our application.