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BQ77915: PRESS Pin Control

eso18
Prodigy 150 points
Part Number: BQ77915

Hi,

I am using BQ77915 for my 4S2P battery.

To switch it for Hibernate mode, the PRESS pin must be left FLOATİNG or LOW. For normal mode, the Press pin should be High(>VPRESH).

I don't want my system to run all the time. That's why I set up a latch circuit on the Press pin. I control the latch circuit with the button. I connected the Latch Circuit output to the Press pin. When I press the button, it goes High and the system switches to Normal mode.

Even if the device goes into hibernate mode, the Latch circuit I set up is always active. It is powered directly from the battery. But the quiescent current is low.

So I have question on my mind.

For the device to work in normal mode, do we have to drive HIGH(>VPRESH) continuously to the press pin (PICTURE 1) ? Is it appropriate to drive HIGH momentarily with the push button (PICTURE 2)?

If the button is driven with a High signal once (like picture 2), I will not use a Latch circuit. due to quiescent current

In short, if I use Picture 2, will the button be permanently off? for normal mode

  • 0
    TI__Mastermind 42060 points

    Hello Eso18,

    To enter in HIBERNATE mode, you have to pull PRESS low or leave it floating, if the pin is pulled high, it will enter NORMAL mode. To enter NORMAL mode, you need to pull-up the PRESS pin and leave it pulled up, otherwise the device will enter HIBERNATE mode again. 

    How it behaves can be read in Section 9.3.5 HIBERNATE Mode Operation from the datasheet. See excerpt below:

    Best Regards,

    Luis Hernandez Salomon