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BQ25120A: Using I2C to enter Low power Chip Mode?

Todd Keppler
Prodigy 180 points
Part Number: BQ25120A

Hi 

Cusotmer has the following question regarding BQ25120A.

" I am trying to finish the design details so we can start layout of our ring main flex with the BQ25120A, but learning this part from the datasheet is very time consuming and I don't want to make a mistake.

 

I am trying for minimal IO to the part. The datasheet says I need to have !MR and !CD high for tReset before shutdown mode can happen. I need my device to enter this mode on its own. The diagram does not show !CD and !MR falling after shutdown mode is entered. In my system, these lines would drop as there is nothing to pull them up. I am disappointed that I have to dedicate IO pins in order to enter shipping mode through I2C. Can you confirm I absolutely have to do it this way. I2C only control is my desire."

 

 

Any way to do this through I2C.


Regards,

Todd

  • 0
    TI__Prodigy 670 points
    Hi, if I2C is your only control, no problem, you can use the I2C command to set the EN_SHIPMODE bit to place the part enter shipmode.
  • 0 in reply to Robin Tang
    TI__Genius 9430 points

    Hi Robin,

    Thank you for the quick help. I'm working on this same issue. Just to clarify, it's clear that the /MR and /CD pins need to be held high during the ship mode command. I see that /MR has an internal pull up so we can leave this floating. /CD is usually pulled up to Vsys. Can you confirm that Vsys will say active for tquiet after the ship mode command is given, so /CD is still held high during the required wait period? 

    Thanks,

    Nate

  • 0 in reply to Nate Enos
    TI__Prodigy 670 points

    Hi, what's mean Vsys will say active for tquiet after the ship mode command is given? If you used I2C to place the part in shipmode, the Vsys will no voltage. nad it's not a proboem that /CD is high or low when bq25120A is already in shipmode.

    Thanks,

  • 0 in reply to Robin Tang
    TI__Genius 9430 points

    Hello,

    Posting to capture this in writing. I confirmed with Robin that Vsys is held up for tquiet after the ship mode command is given since the battery FET is still on. Thus it's possible to put the BQ25120A  into ship mode with only I2C but leaving /MR floating (internally pulled up) and pulling /CD up to Vsys and using I2C to give the ship mode command. 

    Thank you for the help,

    Nate