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Original question:

TPS544C20: TPS544C20 CNTL Pin source current

TPS544B20: Can CNTL pin be left floating for TPS544B20 to operate properly

LALIT VERMA
Expert 1635 points
Part Number: TPS544B20

Hi,

I would like to know whether CNTL pin of TPS544B20 can be left floating so that TPS544B20 can be enabled by default without any programming.

Thanks,

Lalit

  • 0
    TI__Mastermind 48160 points

     

    The TPS544B20's CNTRL pin does not have an intentional pull-up or pull-down.  It is a high-impedance logic input and could drift high or low if left floating.  It should not be left floating.  If the pin is left floating, the TPS544B20 may not enable its output when powered.

    if you want to eliminate a pull-up resistor, the CNTL pin can be connected directly to BP3.

  • 0 in reply to Peter James Miller
    Expert 1635 points

    Hi Peter,

    Thanks for the quick reply.

    It means that the BP3 regulator will start regulating and give the 3.3v output voltage as soon as input voltage is provided to the TPS544B20 and it is not controlled by CNTL pin?

    CNTL pin only control the output voltage of the regulator and can be tied to BP3 to keep TPS544B20 always ON.

    Am I right?

    And one more question:

    Are the SMBus pins : CLK,DATA and SMBALERT_N 5.5v tolerant as per SMBus specification?

    Thanks,

    Lalit

  • 0 in reply to LALIT VERMA
    TI__Mastermind 48160 points

    [LV] It means that the BP3 regulator will start regulating and give the 3.3v output voltage as soon as input voltage is provided to the TPS544B20 and it is not controlled by CNTL pin?

    [PJM] Yes, the BP3 regulator (and the BP6 regulator) on the TPS544B20 are not controlled by the CNTRL function, they are powered nay time the VDD pin is powered.

    [ LV] CNTL pin only control the output voltage of the regulator and can be tied to BP3 to keep TPS544B20 always ON.

    Am I right?

    [PJM] Yes, that is correct.  Connecting the CNTL pin to BP3 will keep the TPS544B20 "Always ON" by default programming.

    Note: It is possible to change the ON_OFF_CONFIG PMBus command so that the TPS544B20 requires the OPERATION command as well as the CNTL pin, or to set the TPS544B20 to not require the CNTL pin, and store those settings to NVM, but this is correct for the default value of ON_OFF_CONFIG.

    And one more question:

    [LV] Are the SMBus pins : CLK,DATA and SMBALERT_N 5.5v tolerant as per SMBus specification?

    Yes, the CLK, DATA and SMBALERT pins of the TPS544B20 are compliant to 400kHz class SMBus specification and are tolerance to voltage upto 5.5V.