My Stm32L0 working without JP6 ON

[raphael declercq]

Posted on March 01, 2017 at 21:36

Hi everyone, i'm currently working with an stm32L053R8 and here's my problem:

My board works without the jumper JP6 on. I don't get why.

By 'it works' I mean I'm able to connect it to STM Studio and read RTC datas without disconnection.

Maybe some components are dead and induce power on VDD even tho the JP6 open?

I would really apreciate your help

Thanks by advance,

have a good night

#power #jumper #jp6

[Jan Waclawek]

Posted on March 02, 2017 at 10:02

What is your board?

JW

[raphael declercq]

Posted on March 02, 2017 at 10:19

it's a Nucleo-L053R8

[Uwe Bonnes]

Posted on March 02, 2017 at 11:31

Why don't you tell that JP6 is the IDD measurement jumper? With JP6 you probably expect the CPU not to work. However any voltage on a pin not 5-Volt tolerant with supply VCC to the target CPU by the pin protection diodes. Both STLink TX and NRST are normally at VCC level and are connected to pins not 5-Volt tolerant. So e.g. these pins or other external connection may be enough to power up the L0. If you put an ampere meter on IDD, this back drive will not happen as long as the voltage drop on the meter is so low that the pin protection diode don't conduct.

[raphael declercq]

Posted on March 02, 2017 at 14:08

So you tell me that if the circuit is open between IDD pins, the board still works? That seems really weird to me. Today I tried with a L073RZ and I am not able to make it work with an OPEN cicuit on IDD. by open i mean no jumper nor AmpMeter between the two pins on IDD. 

I thought the power from the ST-link was brought to the CPU through this contact and from nowhere else. 

[Uwe Bonnes]

Posted on March 02, 2017 at 15:26

Raphael, no, I did not tell that a nucleo board will work with the IDD jumper disconnected. I told that it may work, if back biasing happens and other circumstances apply, like possible the program running on the chip.