BQ25896: BQ25896 efficiency question

Dustin Sun

Expert 1040 points

Part Number: BQ25896

Dear Expert :

May I know why BQ25896 efficiency is bad in 1.3A ?

over 6 years ago

0 Jeff F over 6 years ago

TI__Guru**** 165786 points

Dustin,

To improve current measurement accuracy, the charger turns off part of the battery FET's "fingers" at lower currents, which increases the battery FETs RDSon at these currents. Above ICHRG~=1.3A, the FET is fully on with lowest RDSon.

0 Dustin Sun over 6 years ago in reply to Jeff F

Expert 1040 points

Hi :
What means battery FET's "fingers" ? could you help to explain ?

0 Jeff F over 6 years ago in reply to Dustin Sun

TI__Guru**** 165786 points

Dustin,

When a high current FET is laid out on a chip, there are multiple sections laid out in parallel instead of one big area. Think of it like multiple small FETs in parallel. The IC turns off a bank of those FETs at lower currents in order to improve current measurement accuracy.

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BQ25896: BQ25896 efficiency question