bq24308 / Ron of internal Q1 FET

S.Satoshi

Other Parts Discussed in Thread: BQ24308

Hi Everyone,

Please let me ask about Ron of internal Q1 FET of bq24308. The VDO at 250mA is specified as 75mV max, so I understand that the Ron max at 250mA should be 300mohm. Then is it also the same at 1.5A ? If so, it looks large because the dropout will be 0.45V at 300mohm and 1.5A.

It will be helpful if you can provide the characteristics of VDO vs IOUT.

Best Regards,

Sonoki / Japan Disty

over 9 years ago

0 Roger Hwang over 9 years ago

TI__Genius 10785 points

Sonoki-san,

I don't have the plot but your assumption is correct.

Roger

0 S.Satoshi over 9 years ago in reply to Roger Hwang

Guru 21675 points

Hi Roger,

Thank you for your comment. In the case of standard LDO, the VDO get higher at higher load current. so I believe that VDO of Q1 in bq24308 will be higher than 45mV at over 250mA load. That dropout looks large... however I understood.

Best Regards,
Sonoki

0 Roger Hwang over 9 years ago in reply to S.Satoshi

TI__Genius 10785 points

Hi Satoshi-san,

Can you explain to me the exact concern you have then I can try to comment on it?

Thanks

Roger

0 S.Satoshi over 9 years ago in reply to Roger Hwang

Guru 21675 points

Hi Roger,

I'm concerning that the input voltage to charger IC get lower and it may problem if the voltage will be too low. In the case of very long and/or thin USB cable, the IR drop will be getting large at higher charge current, so the drop out at OVP IC should be low as possible.

Best Regards,
Sonoki

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bq24308 / Ron of internal Q1 FET