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BQ25505 and bq25570 doubts

pipesg
Prodigy 130 points
Other Parts Discussed in Thread: BQ25570, BQ25505, BQ25504

Hi,

I would like to ask you some questions about the BQ25570 and BQ25505.

1-      Is it possible to directly connect VBAT_OK signal to VOUT_EN to control the buck converter? Looking in the electrical characteristics I think should be possible. This option would be included in a solar circuit with MCU-DATAFLASH-GPS, Lipo gauge and a small battery (10-20mah). I have some problems when the device is for a really long periods in the dark to restart and this would allow the circuit to only start working with enough charge in the battery.

2-       I would like to design a board with the minimum components of the BQ25505 and I do not need the VBAT_OK output, is it possible remove the resistors that regulate it in a similar way as explained in the BQ25570 (OK_PROG connected to VSTORE and OK_HYST to GND)?

Thanks in advance!!

All the best,

 

José Mª Abad  

  • 0
    TI__Guru**** 167196 points

    Regarding 1, yes you can connect VBAT_OK to VOUT_EN.

    Regarding 2, if you do not need VBAT_OK, it is best to connect both OK_PROG and OK_HYST to GND and leave VBAT_OK floating.  The next revision of the battery sheet will have this recommendation. 

  • 0 in reply to Jeff F
    Prodigy 130 points

    Thank you very for your prompt and useful reply!!

    The recommendation (OK_PROG and OK_HYST to GND and leave VBAT_OK floating) could also be applied to bq25570?

    One more question, this probably a bit silly (I’m a hobbyist not a professional)so sorry in advance. In the datasheet of Bq25505 and Bq25570, EN, VBAT_OK and VOUT_EN appears as connected to VBAT and VSTORE, does it mean that they should be pulled up with that signals? I have previously used BQ25504 with success but VBAT_OK signal looks different in this way.

  • 0 in reply to pipesg
    TI__Guru**** 167196 points

    The OK_PROG and OK_PROG_HYST  to GND applies to all members of the bq255xx family.

    /EN input pin high voltage threshold is referenced to the VBAT voltage.  The VOUT_EN input pin high voltage threshold is referenced to VSTOR.  VBAT_OK is a push pull output that outputs up to the VSTOR voltage so it can be used to drive VOUT_EN.

  • 0 in reply to Jeff F
    Prodigy 130 points

    Thanks again!!