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Original question:

BQ25504: Are BQ25504RGTR and BQ25504RGTT interchangeable?

BQ25504: BQ25504 charge query

Star Xu
Genius 9645 points
Part Number: BQ25504

Hi

The customer design with BQ25504, the battery is a lithium titanate battery with a full charge voltage of 2.8V. But actually it stops charging at 2.34V.

Attached the schematic for your reference.

Please give some suggestions.

Thanks

Star

  • 0
    TI__Guru*** 144000 points

    Hi Star,

    There are 3 possibilities.

    1. The load on VSTOR and VBAT (including battery leakage) is higher than the input power can support once the battery reaches 2.34V.

    2. Switching noise on VSTOR is not being adequately filtered by the 0.01-0.1uF on VSTOR, thereby causing a shift in the voltage voltage.  Placement of that resistor as close as possible between VSTOR and IC GND (VSS pin) is required.

    3. Parasitic resistors from residual solder flux in parallel with the multi-mega ohm resistors is changing their effective value.  This is explained in the datasheet layout section toward the end of the datasheet.  Quickest way to check is to remove the resistors, use solder flux remover to clean the board and replace the resistors by standing them on their edge to reduce surface area for parasitic resistor connection.  If this is found to be the problem, the the board assembler needs to improve its solder flux removal procedures.

    Regards,

    Jeff