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MSP430F5335: LDOO current draw

JAP
Intellectual 2410 points
Part Number: MSP430F5335

Hi,

I'm working with a design where LDOO is supplied externally. LDOI is connected to GND and internal LDO is disabled. It turned out that LDOO draws tens on mA's current even though it is powering only IO.

Is there someting I'm missing here?

Thanks!

Rgds,

JAP

  • 0
    TI__Genius 13660 points

    Hello,

    Could you please provide more detail as to why the LDO is being externally supplied on the LDOO pin. According to Figure 43.2.2 on the device family user's guide, if you want to power the device using the LDO and an external source, you should supply the source voltage on the LDOI pin and then externally connect the LDOO pin to the DVCC pin. This will then allow the customer to power the MCU when the input source voltage goes above Vlaunch.

    Best regards,

    Matt

  • 0 in reply to Matt Calvo
    TI__Intellectual 2410 points

    Hi Matt,

    Idea is that internal LDO is not used at all. Therefore LDOI in grounded and external rail connected to LDOO to power PU.0 and PU.1. DVCC is powered from other external rail. According to user's guide section 43.2.4 this kind of approach should be supported.

    "There may be applications where the 3.3-VLDO is not required. In these cases, keep LDOI tied low to prevent the 3.3-VLDO from turning on and drawing any current even if LDOEN= 1. If Port U operation is desired, since the 3.3-VLDO is not enabled,an external voltage to the LDOO pin is required."

  • 0 in reply to JAP
    TI__Genius 13660 points

    JAP,

    According to Figure 43-1 of the user's guide, the LDOO pin is internally connected to Port U:

    Has the customer taken all of the necessary steps to properly initialize these special port pins as per the recommendation in Section 43.2.7? The high current draw could be from something that is connected to PU.0 or PU.1.

    Best regards,

    Matt

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