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MSP430G2153 comparator bias current

Andre Pinheiro Fernandes
Prodigy 130 points
Other Parts Discussed in Thread: MSP430G2153, BQ24450, LM393

Hi,

I am planning to interface the MSP430G2153 with bq24450 to read the charge status pins.

The problem is that if I connect directly to STAT1 pin it will mass up the voltage divider. So, I thought that I could use the MSP430 internal comparator to know if STAT1 is HIGH or LOW. Do you whink it is OK? What is the MSP430G2153 comparator bias current?

Thank you!

Andre

  • 0
    Guru 46710 points

    Andre Pinheiro Fernandes said:
    So, I thought that I could use the MSP430 internal comparator to know if STAT1 is HIGH or LOW. Do you whink it is OK?

    I don't think so. STAT1 and STAT2 are open-collector outputs. All you need is to add pull-up resistor (like 10k) between STAT pin and VCC of msp430 and use logical input of msp430 to check the state of STAT1/STAT2.

    Andre Pinheiro Fernandes said:
    What is the MSP430G2153 comparator bias current?

    You can find this info in the datasheet. Max leakage current (with pull-up resistor disabled) is the same for all input types - digital, adc and comparator, it is +/- 50nA (nano Amps).

  • 0 in reply to Ilmars
    Prodigy 130 points

    In fact STAT1 and STAT2 are open drain outputs, but as you can see in Fig10 of bq24450 datasheet, STAT1 is connected in a resistor divider through RD.

    If I draw current from STAT1, the battery float voltage will be affected.

    I have already read STAT1 using a LM393 comparator. What I want to know now is if the internal MSP430 comparator draw <1uA.

  • 0 in reply to Andre Pinheiro Fernandes
    Guru 46710 points

    Andre Pinheiro Fernandes said:
    What I want to know now is if the internal MSP430 comparator draw <1uA.

    As far as I know, 50nA is less than 1uA.

    Ilmars said:
    it is +/- 50nA (nano Amps).

  • 0 in reply to Ilmars
    Prodigy 130 points

    Yes, you are right.

    I was just justifying why do I need a high impedance input. xD

    Thank you.

  • 0 in reply to Andre Pinheiro Fernandes
    Guru 46710 points

    Andre Pinheiro Fernandes said:
    I was just justifying why do I need a high impedance input. xD

    Understood. My fault that I did not read whole datasheet of bq.

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