• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 457 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ40Z80: Using the device as a power switch

Chris Davidoff
Prodigy 220 points
Part Number: BQ40Z80

Hello!

I recently posted a question asking if I could use one of the configurable GPIO pins to use the bq40z80 as a switch (using the bq40z80 as an INPUT).  That wasn't possible.  Perhaps I was asking the wrong question though..

The bq40z80 controls N-channel CHG and DSG FETs as a way to protect from over-charge and over-discharge.  I should be able to use the bq40z80 to turn the CHG and DSG FETs on and off at my own will, to act as a power switch.

Can you recommend the best way to do this?

Perhaps by use of the 'Emergency Shutdown' feature?   Found in the technical reference manual in section 6.6

 


Thanks!

-Chris

  • 0
    TI__Mastermind 24870 points

    Hello Chris,

    It could work, but my only question is how to get the FETs back on. I will check on this for you internally.

    In the mean time, can you try to implement on EVM? I suggest using a differential scope probe to monitor VGS across the FETS when you send a high-low transition on the GPIO pin. After that, I would recommend you provide a low-high transition to see if the FETs turn back on?

    It is not clear to me in that section of the TRM, but I'll submit a ticket to see if we can update the bq40z80 TRM to include it.

  • 0 in reply to Kang Kang
    TI__Mastermind 24870 points

    http://www.ti.com/lit/ug/sluubt5a/sluubt5a.pdf

    To add on:

    Section 6.6.3 has the exit conditions.

    Please try it out on an EVM and your system.

  • 0 in reply to Kang Kang
    Prodigy 220 points

    Kang Kang,

    I have succesfully attempted this on the EVM and it works wonderfully!  I am extremely happy about this, it makes my design much cleaner and efficient.  Now.... If I could control the debounce delay within the Data Memory section of the bq40z80, that would be tremendous!  As it stands, it takes about 1 second to either turn on or off the system by holding down a momentary push button.  This is also specifically stated in the pin functionality (I.E. section 2.6.2 or 6.6.1 or 6.6.3).  If that delay could be altered, to say, 3 seconds, this chip would truly be the dream fuel-gauge IC.  This can be done externally of course, but it means more components.  I'll ask this in a 'related question'.

    If changes are ever made to the Technical Reference manual, I would suggest adding to the beginning of the Pin Configuration section, that a device RESET is required in order for the changes to take effect.