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LPM3 power consumption is too high (F5329)

Other Parts Discussed in Thread: MSP-TS430PN80A

Dear all,

We seem to be unable to lower the power consumption to the level indicated in the datasheet (~2 uA).

The MCU is programmed to turn off all peripherals and timers (which should be off anyway after boot), and to set all pins to low output. When that's done, LPM3 is entered. Here's a link to the code:

http://pastebin.com/S5YDhzrN

When this code is executed on the TI MSP-TS430PN80A board, the power consumption is ~70 uA. On our own board, the consumption is ~95 uA. The theoretical consumption of our board should be ~25 uA, which seems wrt the consumption of the TI board.

All of this seems to indicate that the power consumption of the MCU is around 70 uA, which is way higher than the announced 2 uA. Is there something wrong in the way we handle LPM3?

Thanks in advance for any help.

  • Is the JTAG adapter attached (TEST pin pulled high)?  If so, the DCO keeps running (even in LPM3).

    Also in your code I don't see you stifling the LDO-PWR module, which by default is enabled.  Are you powering that regulator (via LDOI pin)?  If so are you using that regulator for anything?

    Jeff

  • Nope, the JTAG is always unplugged when measuring the current (it indeed induces an over consumption of ~200 uA).

    You're right about the LDO-PWR module, it was still enabled. We're not using the LDO (LDOI is connected to gnd, LDOO is NC), so I turned off the module by setting LDOKEYPID to 0x9628 and LDOPWRCTL to 0 but that didn't change the power consumption.

  • Yes, if the LDO isn't even powered then you don't need to worry about it being "enabled".  (Not true of the '5529 USB module, which watches for power-up events on the LDO supply, costing 20uA.)

    Could it be port J?  Try activating the pull-up or pull-down resistors in port J.  PJREN = 0xFFFF;

    Jeff

  • Unfortunately that didn't change the power consumption either.

    It would have been nice to have TI providing a sample code with power consumption figures for their board (e.g., with this code running on our board, power consumption is expected to be xx uA). That would help to have such reference as a building block...

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