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BQ76952: can not turn on the PDSG pin normally

Allen Lu
Intellectual 2440 points
Part Number: BQ76952

Hi, Dear Experts

 my customer have some questions are as below, and add some my experiment also:

1. BQ76952 cannot turn on the PDSG pin by these below commands :

1st:

0x0093 DSG_PDSG_OFF()

0x0094 CHG_PCHG_OFF()

0x0095 ALL_FETS_OFF()

2rd:

writes the 0x0096 ALL_FETS_ON() command

3rd:

write 0x0097 FET_CONTROL as 0x00 to turn on the fet if other conditions are met

4th:

Write 0x9308  FET Options Register

Bit4 PDSG_EN=1, PDSG FET is turned on before DSG

5th:

test mode:

0x0057 Manufacturing Status() Bit Definitions，BIT5,4,2,1,0=1

0x001C PDSGTEST() Only functional in FET Test mode, toggles PDSG FET state

0x001E PCHGTEST()Only functional in FET Test mode, toggles PCHG FET state

0x001F CHGTEST() Only functional in FET Test mode, toggles CHG FET state

0x0020 DSGTEST() Only functional in FET Test mode, toggles DSG FET state

as the above commands ,my customer feedback that it is still cannot turn on the PDSG pin, but these are ±0.3V changing during the test mode toggling. so is there any ,command like DSG_PDSG_ON()?

Or is there any common code to show us the logic how to turn on PDSG without  turn on every FETs, and turn off the useless FETs one by one？

  • 0
    TI__Mastermind 42060 points

    Hello Allen, 

    Is the customer measuring the PDSG FETs correctly?

    If they're using the EVM they should measure the source-gate voltage across the PDSG FETs through TP23 and TP27.

    Did they modify the Settings:FET:Predischarge Timeout or Settings:FET:Predischarge Stop Delta? If Timeout is set to any value (besides 0), the PDSG will turn ON first prior to the DSG gate for the programmed amount of time. This would happen every time the DSG FET is tasked to turn on. If Timeout is set to 0, it will use the Stop Delta condition to turn off the PDSG FET.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Intellectual 2440 points

    Hi Luis:

     tks for your feedback. 

    as i check with my customer ,i ask them to disconnect the outside circuit and measure the PDSG GPIO individually.  but they dont have the EVM board ,just test on their platform. so for the next step ,i will check to confirm these items:

    1. ask my customer to send the GG and LOG file ,and would you help to check their configuration accordingly？

    2. i will let my customer to confirm the setting of Settings:FET:Predischarge Timeout or Settings:FET:Predischarge Stop Delta.

     

  • 0 in reply to Allen Lu
    TI__Mastermind 42060 points

    Hello Allen,

    If the customer can share their schematic, that would be useful to check that everything is okay.

    Yes sending the GG file would be good to confirm the PDSG settings all correct.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Intellectual 2440 points

    Hi Luis ,after work with customer ,they can toggle the PDSG PIN under test mode. but in normal control mode ,they still got some confusion and ask as below:

    1. does the PDSG FET and DSG FET can open together in a long term cycle?

    2. as the PREDISCHARGE Modes description said :  "If PREDISCHARGE mode is enabled, whenever the DSG FET is turned on to power the load, the device will first enable the PDSG FET, then transition to turn on the DSG FET and turn off the PDSG FET." ,what the time interval between the PDSG and DSG?

    3.if we turn on the PDSG all the time, what `s the disadvantage of this application?

    Tks for your time and confirmation!

  • 0 in reply to Allen Lu
    TI__Guru* 81034 points

    Hi Allen,

    The PDSG and DSG FET cannot be enabled together for a long time. There is no option for this on the BQ76952. 

    The time interval between PDSG and DSG enabling is defined by the Predischarge Timeout register (they can set the Predischarge Stop Delta to zero if they want to control it based on time only). 

    I encourage them to play with this feature on an EVM to understand it better.

    Best regards,

    Matt