Excess Current Consumption Running B-L072Z-LRWAN1 From Battery??

[Andrew Neil]

Posted on December 11, 2017 at 20:21

I have removed all the solder bridges & links to minimise stray consumption.

When I measure the combined current through JP3 and JP1 (ie, MCU & RF), it is ~0.87mA between Tx pulses.

(SB19,14,17 are removed; JP2 is not fitted - so no current to USB_LRA)

But, when I power the board from the battery, and measure the battery current, I see

1.95mA

(SB18 is removed)

The ST LD39050 regulator (U7) is supposed to be ''low quiescent current'': the datasheet says it should only, typically, be taking 100uA at 500mA load - so we should be nowhere near that!

So where is this extra milliamp going??

EDIT

To clarify: the ~0.87mA to MCU & RF is measured while powered from the battery.

#current-consumption #b-l072z-lrwan1 #low-power #current Note: this post was migrated and contained many threaded conversations, some content may be missing.

[Andrew Neil]

Posted on December 11, 2017 at 22:25

Update: When I apply 3V3 at CN13, I also see th

e

1.95mA

[Andrew Neil]

Posted on December 12, 2017 at 17:57

There is a connection from the Target +3V3 to the ST-Link AIN_1 - via R26:

This is not mentioned in the list of ST-Link connections that needs to be isolated when making target  current measurements.

>:(

Removing this reduces the battery drain to 1.48mA - which is better, but still not there yet...

[Andrew Neil]

Posted on December 15, 2017 at 22:26

I just tried with an L152 Nucleo board - which has exactly the same regulator:

I removed R32 and JP6 (also R23 - which, again, feeds the +3V3 to the ST-Link).

With JP6 removed, there should be no load at all on +3V3 - and, indeed, the current into JP5.2 from exactly  the same source is 18uA.

So why is the same regulator, in the same configuration, giving well over an order of magnitude higher quiescent current on the B-L072Z-LRWAN1 ??

:(

[Andrew Neil]

Posted on December 15, 2017 at 22:49

 ,

 ,

Neil.Andrew wrote:

Removing this reduces the battery drain to 1.48mA .

So, with 0.87mA going into the LoRa module RF+MCU, that's ~0.6mA getting 'lost' somewhere.

If I do leave JP1,2,3 disconnected - so no load - I do, in fact, read ~0.6mA drain from the battery.

I now have a second B-L072Z-LRWAN1 and that also gives ~600uA drain from the battery with the LoRa module disconnected.

But - as shown in

https://community.st.com/0D70X000006Sj0JSAS

-

the

same regulator

, in the

same

configuration

, on a Nucleo board draws just 18uA!

Looks like 2 possibilities:

1. There is something else connected on +3V3 which is drawing this 600uA but is not shown on the schematic,

2. There is a fault - perhaps (a) leaky capacitor(s).

[Benjamin Heibuelt]

Posted on January 08, 2018 at 14:04

Hi!

I have the same problem with the current consumption of 0.86mA in Stop Mode on battery. 

Is there a solution??

Thanks!

[Tobias Wedell]

Posted on January 08, 2018 at 14:43

Hi,

maybe it has something to do with my found bug in L071:

https://community.st.com/0D50X00009XkYS9SAN

Try to reset EN_VREFINT bit before entering stop mode. More details in link.Best regards

[Andrew Neil]

Posted on January 08, 2018 at 14:29

No, not yet.

My Distributor can reproduce the problem, and has fed it in to ST - we await the response...

It seems that there are 3 possibilities:

1. We are all missing something on the schematic;
2. The schematic is lying - there is something else there that's taking this current;
3. There is a 'batch' fault with these boards - maybe some high-leakage capacitors ... ?

[Andrew Neil]

Posted on January 08, 2018 at 14:48

No:  because the current is as expected when measure at the JP1-3 test points - so the L072 itself is not the issue.

[Jacques Grandjean]

Posted on March 06, 2018 at 13:33

Hello Andrew,

Same Problem with current consumption.. I found nothing in schematics for undestand where goes this 600uA.

Any News from ST?

Regards,

Jacques