LSM6D3H occasional excessive current

[reineking]

Posted on September 29, 2016 at 21:04

When the force sensor is powered off the LSM is always on and the microcontroller is in sleep mode.  Sometimes

the battery will drain to empty

.  When powered back up the LSM gets hot although it still works.  We usually replace it and all is good.  It connects to the CPU via SPI, SCX/SDX are GND, CS_AUX and INT2 float. The LSM connections look good, no shorts.  I have one now that got hot.  I removed the battery and reinstalled it, power cycled and the LSM did not get hot and hasn't since then.  Is there something we should

do, command wise, before entering power down?  Have you seen this before?

Thanks,

Tom

[Miroslav BATEK]

Posted on October 04, 2016 at 11:15

Can you please share you schematic (at least the part with the LSM6DS3H sensor)?

Best regards

Miroslav

[reineking]

Posted on October 05, 2016 at 00:05

I just noticed I left an S out: LSM6DS3H. I attached the schematic. Thanks for your help.

________________

Attachments :

956-14114C.PDF : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzEo&d=%2Fa%2F0X0000000bK8%2FGUrmxVqQmyR26BtYtOL2cdG52Va5QtaMT0EG5oZRQak&asPdf=false

[Miroslav BATEK]

Posted on October 07, 2016 at 16:39

I don’t see any issue in the schematic. I have never met with this kind of issue but I will double check it with my colleagues.

One additional question when do you power the device again after the battery was drain to empty, do you disconnect the battery and connect different one or do you charge the battery from the USB?

There could be a problem if the Vcc voltage is bellow minimum operating range for long time.

Can you please also share your power down command sequence for LSM6DS3H, just for checking.

Best regards

M

iroslav

[reineking]

Posted on October 07, 2016 at 19:39

I just received another failing unit (very small percentage, but still ...).  I could not charge the battery so I replaced it and the LSM got hot.  I repeated this many times with the same result.  I think you are correct that during the normal battery discharge process the 3.3V supply reduces slowly and the LSM can get damaged.  I'm going to move its supply to the switched 3.3V supply so that it is only on during normal conditions.  I'll reply if this does not work.  We are also in the process of reducing the off current too.  Thanks for your help Miroslav.

Cheers,

Tom

[Miroslav BATEK]

Posted on October 26, 2016 at 19:25

I just received one recommendation from my colleagues to disable I2C (as you are using SPI bus) in CTRL4_C (13h).

 It is just prevention because we don't know how the 

microelectroler's GPIOs

 behaves in sleep mode.

Best regards

Miroslav