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BQ24170EVM-610-15V: BQ24170 Minimum Vin versus Regulated voltage

Samuel Monsalve
Prodigy 40 points
Part Number: BQ24170EVM-610-15V
Other Parts Discussed in Thread: TPS2121, BQ24170

I have been testing the BQ24170EVM. The user guide says that the Vin should be minimum 1V above the regulated charging voltage for the converter to operate properly. I have tested it for 1S and 2S charging application and found the following results:
- For 1S the converter only starts working when the voltage is around 7V, so 2.8V above the 4.2V charging voltage, but it actually continues working below 7V when it has already started operation.
- For 2S found similar behaviour, converter started working at aroun 10V for the 8.4V charging regulated voltage.

The question is: could you please provide accurate information about the minimum Vin at rising edge (minimum Vin for the converter to start) and falling edge (voltage below which the converter stops operating once it had started); for 1S, 2S and 3S charging?

Thank you,

  • 0
    TI__Mastermind 32385 points

    Dear Samuel,

    What is your setup? Do you have a system load, what is your input source, what are the limits on your input source?

    In addition, can you probe the PVCC, AVCC, SW, and SRN pins in both cases? Specifically, please note the PVCC and AVCC voltage at which the converter starts operating.

    Thanks,

    Mike Emanuel

    Please click "This resolved my issue" button if this post answers your question.

  • 0 in reply to Michael Emanuel35
    Prodigy 40 points

    Hi Michael,

    My system load is connected to the TPS2121 evm 10Ohm resistor. I will test it with my actual system load. The input source is a 2S lithium battery, 2Ah. The aim is to charge an extra (with lower voltage) from this input battery, and at the same time power the system.

    A I mentioned, the 2S battery as input to the BQ24170 makes the converter work at 1S configuration when the voltage is within the nominal range of the input battery, around 7V. 

    I will find the values by testing with the constraint system, since I am guessing there is no an universal answer.

    Thank you very much.

  • 0 in reply to Samuel Monsalve
    TI__Mastermind 32385 points

    Dear Samuel,

    Can you obtain waveforms of the above pins, not just the DC values? This would be more helpful to understand the behavior of the part.

    In addition, can you provide more details as to how you tested when the converter turns on? You said the converter works within the nominal range of the input battery, 7V, but not some lower inputs. Did you discharge the battery to test the lower voltages?

    Can you test the input of the converter with a DC power supply and see if you can get the converter to turn on at a lower voltage?

    Thanks,

    Mike Emanuel

    Please click "This resolved my issue" button if this post answers your question.