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BQ25505: Inquire about BQ25505 or BQ25504 differences and design

Part Number: BQ25505
Other Parts Discussed in Thread: BQ25570, BQ25504,


The BQ25570 circuit I asked you about earlier works well because the problem has been solved.

When applying mass production products, the circuit is changed, so the output of BQ25570 is not required, so we would like to change it to BQ25505 or BQ25504 to reduce the cost of parts.

I can't decide which one suits my purpose, BQ25505 or BQ25504, so please advise which one would suit me better.

1. Li-po 130mAh Li-Po


3. 2.4V Indoor Small Solar Cell

In addition, I would like to ask if it is correct to attach a diode to the battery input and output as shown in the picture.



  • Hi JP,

    The BQ25504 and 505 have the same boost converter.  The 504 has adjustable BAT UVLO (voltage at which the PFET between BAT and VSTOR stops discharge from BAT to VSTOR) while the 505 has fixed UVLO at 2.1V.  The 505 also has MUX to switch between the rechargeable battery and a primary non-rechargeable battery.  If not needed as a MUX, since one of the MUX outputs is an inverse of the BAT_OK output, which some customers use to control an external PFET that isolates the load on VSTOR until the battery voltage is high enough.

    Regarding the diodes, I don't see a need for them.  The BQ2550x internal PFET body diode prevents reverse current.  The TPS7Axxx has reverse current protection as well.



  • Thx Jeff