BQ2057C: BQ2057C little charge current

Part Number: BQ2057C

Hi

 My customer use BQ2057C to charge battery. The current sense is 0.1 ohm, transistor is FZT788B, the actual charging current is only about 200mA in the case of 5V voltage, and can rise to more than 400 mA when it reaches above 5.4v, how should I modify the circuit?

Thanks

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