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BQ24170: Question about reducing leakage current

Chase Jeong
Genius 5420 points
Part Number: BQ24170

Dear TI experts,

My customer is trying to reduce leakage current of BQ24170, and they had some tests.

Could you check that thest tests are available and okay to apply next PCB version?

First refer the schematic below;

1. They removed R33 -> reduced 1.1uA. -> Is it okay to remove?

2. They removed R32 -> reduced 12.1uA -> Is it okay to remove? I cannot find this resistor in reference schematic.

3. They removed R24, R22 -> reduced 2uA -> Is it okay to remove?

4. They removed Q6 -> reduced 7.1uA -> Is it okay to remove?

4-1. They saw 7.1uA leakage current with Q6 attached amd R18 NA.

4-2. They saw 8uA leakage current with Q6 attached and R18 50Kohm.

4-3. They saw 0.5uA leakage current with Q6 attached and R18 10Mohm.

-> So if I cannot remove Q6, Please check the best value of R18 resistor.

Best regards,

Chase

  • 0
    TI__Guru**** 150335 points

    Hi Chase,

    Regarding 1, no.  The low pass filter created by 10ohm and 0.1uF is required.  It has minimal effect on Iq.

    Regarding 2, I do not know.  I do not understand its purpose.  This part is so old there is no one left to ask.  It is not used on the 5V input EVM but is on the 12V input.  I recommend keeping it.

    Regarding 3, R22 is the sense resistor used to measure charge current.  It is required.

    Regarding 4, Q6 is the battery FET that connects the battery to the system load at V_charge.  It can replaced with Schottky, if the system can afford the diode voltage drop.  If there is no load connected at V_charge or that load isn't intended to be powered by battery only, then Q6 can be removed.

    Regarding 4.x, R18 of 10k is only needed for 1S applications.  Per 3S EVM, it can be replaced with 1Mohm.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Genius 5420 points

    Dear Jeff,

    Thank you for your support, and hope you had a good weekend.

    My customer have some more questions about your answers. Could you check it?

    Regarding 4, Q6 is the battery FET that connects the battery to the system load at V_charge.  It can replaced with Schottky, if the system can afford the diode voltage drop.  If there is no load connected at V_charge or that load isn't intended to be powered by battery only, then Q6 can be removed.

    -> Coul you provide the schematic of replaced with schottky and Q6 removed? Hahd-writing schematic is also fine with me.

    Regarding 4.x, R18 of 10k is only needed for 1S applications.  Per 3S EVM, it can be replaced with 1Mohm.

    -> My customer uses 2S1P battery. How about the value of R18 in this condition?

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Guru**** 150335 points

    HI Chase,

    Regarding 1, 


    Regarding 2, R18 can be 1 Mohm or open.

    Regards,

    Jeff