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AM4377: Simplified Power Sequencing

Bernd Sprenger
Intellectual 340 points

Part Number: AM4377

I am designing a board with the AM4377 using Simplified Power Sequencing and a discrete power supply. In the datasheet p.125 it is noted that " VDDS, VDDS_CLKOUT terminals are powered
by shorting them to CAP_VDDS1P8V_IOLDO".

On the AM4377 there are some more power supply pins that have to be powered with 1.8V and are also named VDDS_*:

VDDS_RTC
VDDS_OSC
VDDS_SRAM_CORE_BG
VDDS_PLL_MPU
VDDS_SRAM_MPU_BB
VDDS_PLL_DDR
VDDS_PLL_CORE_LCD

Can they also be powered to CAP_VDDS1P8V_IOLDO instead to another external 1.8V voltage regulator?

(On the Am437x_IDK they are powered by an external regulator)

Thanks a lot for your help - regards,

Bernd

  • +1
    TI__Guru 63635 points

    No.

    The VDDS and VDDS_CLKOUT power rails must be sequenced along with the 3.3V supply so this internal LDO was provided to ensure these two 1.8V power rails ramp up/down with the 3.3V rail. However, it does not have enough current capacity to source any other 1.8V rails.

    You must provide a separate power source for the other 1.8V power rails.

    Regards,
    Paul