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TIDEP-0091: LDO bypass setting

Dave Ochs
Prodigy 250 points
Part Number: TIDEP-0091
Other Parts Discussed in Thread: IWR1443, IWR1443BOOST

Hi,

Can you please explain why the the IWR1443 LDO bypass is disabled by default when the LP87524J is used in auto mode? Isn't the output voltage of Buck2 1V no matter which mode the PMIC is operating in? Why would we set the LDO bypass to true only if the PMIC is in forced PWM mode, as the comments in the code say to do?

Thanks,

Dave

  • 0
    TI__Guru 50240 points
    Hi Dave,

    The IWR1443BOOST Rev A board comes with the LP87524B PMIC and if LDO Bypass is enabled then there is high risk for damage to the board. Since modification of the EVM is required for use of the LP87524J PMIC, we have disabled the LDO Bypass as a default. If you have installed the LP87524 J PMIC then you should enable LDO Bypass.


    Cheers,
    Akash
  • 0 in reply to Akash Gondalia
    Prodigy 250 points

    Hi Akash,

    If I'm reading the IWR1443 datasheet correctly, it seems like the LDO bypass should be enabled if the PMIC, no matter which one, can supply 1V to : VIN_13RF2, VIN_13RF1. Do you mean that if the LP87524J PMIC is used with the default configuration, the LDO bypass should be enabled? Or more specifically: if BUCK2_VSET in the LP87524J is set to 1.0V, the LDO bypass should be enabled?

    Thanks,

    Dave

  • 0 in reply to Dave Ochs
    TI__Guru 50240 points
    Hi Dave,

    Yes this is correct. If BUCK2 is set to 1.0 then LDO bypass should be enabled.

    Alternatively if the MSP432 is used to program the PMIC into PFM mode then BUCK2 should be set to 1.3 V and LDO Bypass disabled.


    Cheers,
    Akash
  • 0 in reply to Akash Gondalia
    Prodigy 250 points

    Why can't PFM mode be enabled if BUCK2 is 1.0V?

    Thanks,

    Dave

  • 0 in reply to Dave Ochs
    TI__Guru 50240 points
    Hi Dave,

    This is the recommended setting because it allows us to get some Line Rejection from the PMIC output, the internal RFLDO wil lconvert 1.3v to 1.0v.

    There is a slight power increase but it protects the radar 1.0v rom PFM/PWM spikes somewhat.


    Cheers,
    Akash