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BQ25703A: some question about 25703A

maceti
Prodigy 230 points
Part Number: BQ25703A
Other Parts Discussed in Thread: BQ24610, BQ24773

I have some question about BQ25703A;

1- I am using 1 cell 18650 Li-Ion battery( max 4.2V) and my input voltage is 5V-21V. So, I will use it in buck mode every time. Is it possible to use it without boost mode MOSFETs. Because my design is space sensitive.

2- As I said in my 1. question, I am using 1 cell 18650 Li-Ion battery( max 4.2V) and my input voltage is 5V-21V. So, I will use it in buck mode every time. And I don't need independent comparator, PROCHOT, IADPT, IBAT function. I am using BQ25703A because I need high current output and DPM. Do you have any alternative suggestion for my specification?

3- When I look at the EVM Design for CELL_BATPRES Pin resistors, for 1 Cell battery, I saw 400k (280k+120k) and 100k resistors used. With this combination, CELL_BATPRES pin getting %20 VDDA voltage, right? I think 300K and 100K should be used for %25, right?

4- In the EVM Desing, many capacitors used in 0603 packages. Can I use these capacitors with 0402 packages? (With same voltage, tolerance same etc.)

thanks.

  • 0
    TI__Mastermind 25800 points

    Hey MAHMUT,

    For 1) No, the boost mode MOSFETs are required for operation.

    For 2) I would suggest something like a standalone charger like the BQ24610. But it you need some I2C control, you may also consider the BQ24773 which is only a buck-mode NVDC charger. 

    For 3) In the datasheet for the BQ25703A, the % window for the CELL_BATPRESZ pin setting for 1S is between 18% and 31%. In reality, the CELL_BATPRESZ voltage cannot fall below 15% or else it will be detected as a battery removal event. So 20% is perfectly acceptable. 

    For 4) Yes, but keep in mind that 0402 capacitors tend to have a much steeper DC derating factor than 0603 packages. In factor, package size greatly influences the DC derating.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Prodigy 230 points

    Thanks for the reply and great support!