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BQ20Z65-R1: PERS# pin status

Thomas CN1
Intellectual 300 points
Part Number: BQ20Z65-R1
Other Parts Discussed in Thread: BQ20Z60-R1

Hi,

1) 

BQ20Z65-R1 data sheet  Figure 2-4. AFE Discharge Overcurrent Protection mentions as:  Reinsert Battery Pack [PRES#] transitions from 0 to 1

But section 2.8.2.1 Battery Pack Removed explains as: The bq20z60-R1/bq20z65-R1 detects the Battery Pack Removed mode if the [NR] bit is set to 0 AND the PRES# input is high ([PRES] = 0)

Aren't these statements contradicting? And which is correct? Hope the battery is detected as present when the PRES# signal is LOW and [PRES] bit is HIGH in this condition. Please confirm.

2) 

Also section 2.8.3 Sleep Mode explains as: If the [NR] bit is set to 0, [PRES] must also be set to 0 for the bq20z60-R1/bq20z65-R1 to enter sleep. AND one of the following conditions:

Is this means the PERS# signal has to be HIGH (battery removed condition making [PRES] bit as LOW) for entering into sleep mode? 

Regards,

Thomas CN

  • 0
    TI__Guru 57747 points

    Hello Thomas,

    The PRES pin is active low and the PRES bit is active high. You understood correctly - the battery is detected as present when the PRES signal is LOW and [PRES] bit is HIGH in this condition.

  • 0 in reply to Shirish
    Intellectual 300 points

    Hi Shirish,

    Thanks for the clarification. Can you please confirm on the second question also? 

    Whether the PERS# signal must be HIGH (battery removed condition making [PRES] bit as LOW) for entering into sleep mode? 

    Is there any way to enter into sleep mode if the PRES# signal is LOW?

    Regards,

    Thomas CN

  • 0 in reply to Thomas CN1
    TI__Guru 57747 points

    If NR=0, then correct. PRES signal must be high for entering sleep mode.

    Note that in sleep mode the FETs are turned off, so the system will lose power.

    Setting NR=1 will ignore the PRES pin signal in most cases(please read TRM for specifics). You can send the ManufactererAccess() Sleep command to enter sleep mode.

  • 0 in reply to Shirish
    Intellectual 300 points

    Hi Shirish,

    Thanks for the clarification.

    If NR is high, will the below condition also causes to enter into sleep mode or the Manufacturer Access Sleep command is the only possible method?

    (|Current| ≤ Sleep Current) AND (SMBus is low for Bus Low Time) AND (the [SLEEP] bit is set)

    Regards,

    Thomas CN

  • 0 in reply to Thomas CN1
    TI__Guru 57747 points

    Hello Thomas,

    I don't see that condition specified in the TRM but i think that it will enter sleep mode if other conditions are met. (NR=1 should result in PRES state ignored).

  • 0 in reply to Shirish
    Intellectual 300 points

    Hi Shirish,

    Thanks for the reply.

    Is there a way to check if the BQ20Z65-R1  is in sleep mode?

    This query has been raised based on on one issue we have: Our battery pack is getting very quick self discharge and going into deep discharged state, and we are suspecting the BQ20Z65-R1 is not entering into sleep mode and draining the cells. I will share our BQ20Z65-R1 design. Can you please review and let us know if there is any issue in our design? Especially on the PRES and ALERT pins which we have tied to GND. Whether the ALERT pin has any connection with the sleep mode?

    Please reach me by email on thomas.ninan@ge.com  so that I can reply you with the schematics attachment. I cannot attach files here in forum due to the organization's network restrictions to upload files to external websites.

    Regards,

    Thomas CN

  • 0 in reply to Thomas CN1
    TI__Guru 57747 points

    Hello Thomas,

    Current consumption is the best way to know if bq20z65-R1 is in sleep mode. Other quick ways to check if the cells are self discharging is to disconnect the gauge power. Then check there is any other current path. If not, then wait and check if self discharge is observed even without the gauge.