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TPS25942A: For single or double cell li-ion battery UV/OV/OC and reverse battery protection

Danlin Xiang
Prodigy 70 points
Part Number: TPS25942A
Other Parts Discussed in Thread: TPS259230-41EVM

Hello,

I would like to use TPS25942A for single (18650) or double (2x16340) cell li-ion battery UV/OV/OC and reverse battery protection for a portable measurement product. The input voltage range is between about 3V (the low end of single cell) and 8.4V (the high end of 2-cell). The datasheet is well explained about UV/OV/OC  protection. But for reverse battery protection, there is only very brief information in section 10.3.1.4 and Figure 86.

My questions regarding Figure 86 are:

1. Because the signal diode in the GND terminal path, would the input voltage shifted higher of Vf of the diode instead of 2.7 to 18V without the diode?

2. What impact of the calculation of UVLO, OV dVdT, ILIM, and IMON because of the signal diode in the GND terminal path?

3. Should the thermal pad of the chip be connected to the GND of the chip (pin16) then to the PCB ground plane through the signal diode, or connected to the PCB ground plane directly?

Thanks,

Danlin

  • 0
    TI__Guru* 95891 points

    Hi Danlin,

    Thanks for reaching out.

    1A) The working voltage range between IN and GND pins remains same  i.e., 2.7 to 18V

    2A) The calculations for UVLO, OV, dVdT, ILIM, and IMON are referenced to GND. Now, as shown in the below figure, the input voltage becomes IN=VB-VD  instead of VB. The equations given in the datasheet can be used by subtracting signal diode drop from the input source VB.

    3A) Connect the thermal pad to GND  pin(pin 16) and then to the PCB ground plane through the signal diode. Please make a copper island for the thermal pad for thermal relief. You may like to look at examples Figure 6, Figure 7 in

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Prodigy 70 points

    Thanks Rakesh for the quick response.

    The low end of the input voltage range VB is 3V in my design, which is pretty close to the 2.7V Vin min. of TPS25942. Should I use a Schottky diode to have low VD in your highlight? How about use a small MOSFET here as an ideal diode to have minimum VD?

    Thanks,

    Danlin

  • 0 in reply to Danlin Xiang
    TI__Guru* 95891 points
    Hi Danlin,

    Yes, I recommend to use a small MOSFET instead of diode to have lower voltage drop, something like shown in Figure 1. TPS259230-41EVM Schematic www.ti.com/.../sluuba0a.pdf

    Best Regards,
    Rakesh