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BQ76952EVM: When PDSG_EN is １, how do i use FET_CONTROL ?

Sho Takayama
Intellectual 390 points
Part Number: BQ76952EVM

Tool/software:

Hi

I use FET_CONTOL(DSG_OFF=0, PDSG_OFF=1, CHG_OFF=1, PCHG_OFF=1)   when DSG_FET is ON.
If PDSG in FET Option, how do I use FET_CONTROL to be enable DSG_FET?

  FET_CONTOL(DSG_OFF=0, PDSG_OFF=1, CHG_OFF=1, PCHG_OFF=1):
 How does PDSG_FET operate?

Tankyou,

Sho Takayama

  • 0
    TI__Genius 17655 points

    Hi,

    Today and tomorrow (Dec. 24-25) are U.S. holidays. The team will be back in office on Thursday and will get back to you then.

    Thank you for your patience.

  • 0 in reply to Alexis_H
    TI__Genius 17655 points

    Hello Sho,

    Thank you for your patience.

    Sho Takayama said:
    If PDSG in FET Option, how do I use FET_CONTROL to be enable DSG_FET?

    Writing a 1 to the DSG_OFF bit should allow the DSG FET to turn on if other conditions are met. When FET Control subcommands are used to disable a FET, a signal is latched, which blocks the FET from being enabled.

    You need to clear any signal ‘blocking’ the FET using the appropriate FET Control subcommand. One example is using the subcommand, 0x0096 ALL_FETS_ON().

    This is further mentioned in Section 5.2.3.2 FET Control in the BQ76952 Technical Reference Manual in the paragraph before Table 5-8. FET Control Subcommands.

    Sho Takayama said:
      FET_CONTOL(DSG_OFF=0, PDSG_OFF=1, CHG_OFF=1, PCHG_OFF=1):
     How does PDSG_FET operate?

    Table 12-29. FET Control Register Field Descriptions in the TRM shows what each bit does in 0x0097 FET_CONTROL().  

    When PREDISCHARGE mode is activated, the device remains in this mode until either one of these conditions occur:
    1. Timeout is reached
    2. Voltage at the LD pin rises to within a programmable delta of the top-of-stack voltage
    3. Both

    More information on this is further mentioned in the second paragraph of Section 5.2.3.2.2 PREDISCHARGE Mode in the TRM. 

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Intellectual 390 points

    Hello Alexis

    Thank you your response.

    I understand that PreDischarge mode is a function PDSG is ON for a certain period of time (Settings:FET:Predischarge Timeout) when DSG is tuened ON.

    How should I use FET_CONTROL() to work PreDischarge mode when all FETs are OFF?
    FET_CONTROL(DSG_OFF=0, PDSG_OFF=1, CHG_OFF=1, PCHG_OFF=1) ?
    Or
    FET_CONTROL(DSG_OFF=0, PDSG_OFF=0, CHG_OFF=1, PCHG_OFF=1)?

    Best Regards,

    Sho Takayama

  • 0 in reply to Sho Takayama
    TI__Genius 17655 points

    Hello Sho,

    Sho Takayama said:
    How should I use FET_CONTROL() to work PreDischarge mode when all FETs are OFF?
    FET_CONTROL(DSG_OFF=0, PDSG_OFF=1, CHG_OFF=1, PCHG_OFF=1) ?
    Or
    FET_CONTROL(DSG_OFF=0, PDSG_OFF=0, CHG_OFF=1, PCHG_OFF=1)?

    The second one should be what you want with FET_CONTROL(). Something to note is that the FETs can only be enabled if nothing exists to block them (such as the latched FET Control subcommand signal, CFETOFF/DFETOFF signal is asserted, or a separate enabled safety fault is present). 

    Make sure PREDISCHARGE mode is also enabled through the Settings:FET:FET Options[PDSG_EN] as well.

    I will double-check somethings in the lab and with my team when they are available.

    Best Regards,
    Alexis