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Q: BQ24450 as a charge controller with MOSFET - Regarding
I am looking at using BQ24450 as a charge controller to charge Lead Acid Batteries at a maximum charge current of about 12Amps. I found from the datasheet that by using a Quasi-Darlington pair of transistors, the charging current can be increased up to 15Amps. (Page 14, SLUS929A –APRIL 2009–REVISED JANUARY 2010)
Can the Quasi-Darlington be replaced by a power MOSFET that can handle high current and will be less lossy?
A: Re: BQ24450 as a charge controller with MOSFET
The bq24450 can be used with a P-CH FET. If a FET were used, I would recommend the common-emitter PNP configuration and a P-channel FET. Note that an N-channel can't be used, as there is no way to boost the gate drive voltage. A pull-up resistor would be required from the gate of the FET to Vin. This is what turns off the FET when the bq24450 lets go. A maximum value for this resistor would be the desired response time of the FET on turn off and the minimum value would be the sink capability of the driver in the bq24450.
We have no data on line transient response. But, at 0V in, the IC will be off. An RC filter can always be added to the IN pin to make the circuit more robust from line disturbances.
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