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MSP430F5257: Increased power consumption when pulling up P5.5/XOUT to 1V8

Part Number: MSP430F5257

Recently we noticed a strong power consumption increase in a new revision of an existing product based on the MSP430F5257. The product normally uses around 15uA in sleep mode, the new revision product uses around 150uA.

We traced this back to a change in the components connected to the P5.5/XOUT pin. This pin is configured (in sleep mode) as input GPIO with in the new revision an external pullup to 1.8V which the old version does not have. When experimenting with the pull up voltage we noticed: 0.8V to 1.65V additional power consumption: 0 to 120uA and 1.65V to 2.5V additional power consumption 120uA to 0.

In our opinion all related registers are configured correctly.

Details

XT1 is OFF. P5.4/XIN not connected and set as GPIO output tot '0'. P5.5/XOUT as GPIO input, no internal pull up/down configured.

DVCC: 3.3V

DVIO: 1.8V

What can be causing this increased power consumption?

Is this expected behaviour?

  • Hi Jeroen,

    What frequency are you running at in active mode? It sounds like the device is in active mode. At 1MHz, this would explain the 150uA that you are seeing.  If you disable all of your GPIOs and interrupts, do you still see the 150uA of current consumption? 

    I wouldn't expect to see this much current consumption while in sleep mode.  I'm wondering if something has caused the microcontroller to come out of sleep mode.

    BR,
    Leo

  • Hi Jeroen,

    I'm wondering if UCS9 in the Revision S errata might relate to the issue you are seeing(is the new revision you are using Revision S?):

    https://www.ti.com/lit/er/slaz534s/slaz534s.pdf 

    BR,

    Leo

  • Hi Jeroen,

    how do the P5SELx register settings look like can you please post this piece of the code?

    Also would be interesting if this appears on all devices or only on some?

  • Jeroen,

    I think I have the problem. The point is you pull P5.4 to 1.8V but the Port 5 is a 3V port and not a DVIO supplied port see datasheet extract below.

    When you apply a value around DVCC/2 like 1.8V for DVCC of around 3V your input schmitt trigger generates cross currents because you apply a level exactly in the middle of the threshold of the schmitt trigger. So if you want to use P5.4 as input with external pull up pls apply DVCC otherwise you need select a pin from the blue marked ports below.

  • Hi Leo,

    thank you for pointing out errata UCS9.

    It sure does look related, however we are not using LPM4 but LPM3 and we are not using the XT1BYPASS functionality since it is configured as GPIO. 

    Futhermore the previous revision of the product also had external input on this pin when in LPM3 mode, the main difference is the level. Previous product revision 0 .. 3.3V, new product revision: pullup to 1.8V

    So in my opinion this does not explain our observations.

    Best Regards,

    Jeroen

  • Jeroen,

    your comment "Futhermore the previous revision of the product also had external input on this pin when in LPM3 mode, the main difference is the level. Previous product revision 0 .. 3.3V, new product revision: pullup to 1.8V" finally confirms what I posted before this pin is 3.3V pin and not 1.8V so pulling it to 1.8V with a pull will cause cross currents as described above.

  • Hi Dietmar,

    thank you for pointing this out, this explains our observations and I agree on the proposed solution

    Best regards,

    Jeroen

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