BQ24450

Vladimir Naumenkov

Other Parts Discussed in Thread: BQ24450

Dear sir, please answer

I need to charge 1 cell lead battery (2V). I need 2.5 A charging current, then I set sensing R1=0.1 Ohm. Please see attach.

QUESTION: Does the VD1 need? If 5 V off and battery is not charging (and discharging) I need to minimize the possible discharge current through the BQ24450 and VT1. I used previously the same scheme but with a R1=0.4 ohm (and now I need R1=0.1 Ohm) and then present VD1. But at the 2.5 A current VD1 will be very hot and can it be removed? Or if to remove VD1 is leakage through VT1, when 5 V is off? Even 1 mA leakage is unacceptable for me.

TIA

Sincerely

Vladimir NaumenkovBQ24450.docx

over 8 years ago

0 Jing Zou over 8 years ago

TI__Mastermind 20530 points

For linear charger, we do not recommend to charge it over 1.5A. The power dissipation is going to become heat, in your case, (5V-2V)*2.5A = 6.25W. The loss will be distributed through the charging path.

The diode is used to blocking any leakage current from the battery to the sensing circuit when no input is attached.

0 Vladimir Naumenkov over 8 years ago in reply to Jing Zou

Expert 2970 points

Dear Jing, thank you

As I understand from your answer, VD1 need for blocking leakage. Good. As to power 6.25W, I can install transistor and diode on the heatsink 7W ?

Thank you.

Sincerely,

Vladimir Naumenkov

www.agat.by

0 Vladimir Naumenkov over 8 years ago in reply to Vladimir Naumenkov

Expert 2970 points

Dear Jing, could you please recommend PNP transistor in TO220 case (or in other case, that can be mounted on the heat sink ) wich I can use for 2.2-2.5A charger together with BQ24450?

Power management

Power management forum

BQ24450