Talk² Forum

I'll do some testing over here. Now, just to confirm, in a previous post you mentioned:

"When measured with VBAT I got somewhere 7 and 8 microAmps.", but that does not match your schematic. Could you please confirm?

Also, there's no real reason to connect the batteries to 3.3V directly. This would result in getting some low voltage to the board and things might not work correctly. The ways to power the board are:

Option 1: 3.4V to 5.5V to VIN
Option 2: 3.3V down to 0.9V to VBAT (the minimum voltage will depend on the current)
Option 3: exactly 3.3V to the 3.3 Rails

Did you have a chance to measure the voltage at the VBAT terminals at the same time you measure the current? This would make sure the connections are fine and there's no voltage drop from the batteries to the board.

When everything is powered down, the VBAT should show a consumption of around 6uA (if nothing else connected and no RTC chip installed). Even with some variations, the figures of over 40uA is not normal... let's see if we can find what's going on.

Thank you for your reply.

7-8 microAmps I got was when connecting through 3.3 V pin directly in the previous post, that was my mis-understanding.

I have two Whisper boards I got 44microAmps through VBAT when connected as in schematic above. I just now tried on the other whisper board with that I am getting, 12-16 microAmps, continuously varying, with the same connections.

Yes I measured the voltage when measuring the current, the voltage was at 2.9 V.  I checked with new Duracell batteries also if that made a difference but no change was observed.

Regards

Hi nashdwaj,

Strange the boards have shown different results, especially a very subtle difference like that. Have any modification/soldering/etc done to the other board?

In any case, I've uploaded a video showing the current measuring tests:


ps.:  I would say the 12-16 microAmps is within the normal measurable range. Because of the nature of the switching regulator, measuring an absolute average consumption is not straightforward. High and low peaks occur very quickly (up to 500KHz for the MCP16251), being difficult to sense with non-specialized measuring equipment.

Regards,

Thank you for a nice video.

The difference between the boards is that, the one which had 45uA when powerdown has the female 2 pin JST 2.5 mm soldered at P5.

Nothing connected to it, when measured.