I'm working with a custom board using the MSP430F5528 and running into a issue with current draw in LPM3. I can verify that the board is going into a low power mode since current draw drops from a few mA to around 600uA, but that 600uA is more than I expect the part to draw in LPM3. Note that this current draw is an isolated measurement at the DVCC pin.
I've also put together a simple application that just boots the board and puts it into LPM3 and I get the expected ~1uA current draw, so I know there aren't any hardware issues. I've also addressed the usual suspects for this issue: I'm doing the measurements with the UIF disconnected, and all the unused GPIOs are set as outputs.
Hi Nick,
Sounds like an on-chip peripheral is preventing LPM3 entry. The peripherals can issue "clock requests" that keep the DCO running even when you set the SR for LPM3.
Have a look at any Timer or USCI usage. If they are clocked by the DCO (typically via SMCLK), they might be the problem.
Jeff
This question is being handled offline. Will update with relevant information when we reach a conclusion.
Since more than 5 months have lapsed can we have an update? I'm having a similar issue with my F2491 which still uses about 80uA when in LPM3 so knowing what others had to do to solve their problem might help me solve mine...
First, an update to the previous issue:
The previous 600mA draw was a result of the UCS6 errata which continues requesting SMCLK if using UART and entering LPM3. The details can be found in the erratasheet.
Jean-Michael,
80uA sounds like a pullup resistor is not accounted for somewhere.If you set all GPIO to output low, will you check for any pullup resistors? A 47K pullup will draw ~80uA of current if the GPIO is set low. Find this pin and set that pin output high instead.
Hi Mike,
Thanks for the update. It was indeed a 47k that hadn't been removed... Mind you with 0402 size components the resistor is barely visible to my bespectacled eyes :)
Jean-Michel RubillonMind you with 0402 size components the resistor is barely visible to my bespectacled eyes :)
This this one or this one. Virtually turns the 0402 into 0804 parts. Once, I had to solder them manually, because teh distributor delivered the wrong size and we needed them. I msut admit, it took several tries :)
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Jens-Michael Gross You wear the wrong spectacles. This this one or this one. Virtually turns the 0402 into 0804 parts. Once, I had to solder them manually, because teh distributor delivered the wrong size and we needed them. I msut admit, it took several tries :)
You wear the wrong spectacles.
Thanks for the tip. The MaxiDetail look quite good as well as being practical.It does take a very steady hand to solder those 0402s by hand indeed. I just got an RF development kit that uses 0201 passives. Well I'll take their word for it as all I see is a dot sat on a track. I'd hate to have to build one of those by hand I definitely would need to use our inspection microscope for that task and have been off the coffee for a while :(
Jean-Michel RubillonI just got an RF development kit that uses 0201 passives.
Thankfully I won't have to build one by hand... It came nicely assembled by the supplier.
But all of this is waaayyy off topic so we'll leave it at that.