Lowering the standby power consumtion

[JHRoadrunner]

Hi guys,

first of all thank you for your effort you have put in this project, I built 4 and they work absolutely great!

BUT... :P
... it drains 50 mA in Standby mode, which causes the battery to fail when the car is not driven that much. (No worries Seth, I knew that would happen)
I guess the power consumtion issue might not be relevant for most of you, but in my case it would be nice to not having to unplug the module.

Since the controller and the RN52 are already going in sleep mode the only significant power consumer left has to be the OP-AMP, right?
It has to pins to bring it into power-down-mode, but these are currently not in use.

Have you ever considered using the PD-Control of the OP-AMP, or is there a reason why it isn't used?

I just wanted to check before i start testing it myself.


Greetings
Jan

[Seth]

I just looked into the op amp data sheet and it looks like the op amp only pulls 2.6mA at most.

Putting it in sleep mode would drop it to 20uA, but I don’t think that drop in current would be significant enough to make a difference...

Karlis may chime in, he’s been working on some sleep mode changes for the v6 modules but I don’t think he’s done yet.

If you need to unplug the module due to not driving for some time, you might be better off installing a switch inline with the power wire...?

Seth

On Sun, Nov 29, 2020 at 08:31 JHRoadrunner [via BlueSaab Forum] <[hidden email]> wrote:

Hi guys,

first of all thank you for your effort you have put in this project, I built 4 and they work absolutely great!

BUT... :P
... it drains 50 mA in Standby mode, which causes the battery to fail when the car is not driven that much. (No worries Seth, I knew that would happen)
I guess the power consumtion issue might not be relevant for most of you, but in my case it would be nice to not having to unplug the module.

Since the controller and the RN52 are already going in sleep mode the only significant power consumer left has to be the OP-AMP, right?
It has to pins to bring it into power-down-mode, but these are currently not in use.

Have you ever considered using the PD-Control of the OP-AMP, or is there a reason why it isn't used?

I just wanted to check before i start testing it myself.


Greetings
Jan

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NAML

[JHRoadrunner]

yes you are right, the datasheet says, that it needs 1,25A(worst case) per channel with no input signal.

But what is it then?

Does anybody know right of the hand what drains the most current in standby mode?
Im just trying to avoid deep datasheet digging if possible :D

A killswitch is my last option... thats too easy:D

Jan

[Karlis]

Just my two cents here...

I’ve done quite a few measurements and so far I suspect STM32 being always on as one of the hungry beasts on the module. This is good news as it can be fixed with a firmware update. STM32 has a few low-power modes that can be implemented.

The tricky bit is to do so without upsetting the rest of the car (every node on the bus has to continuously announce it’s presence on the bus). This can be done by putting STM32 to sleep and then waking it up every second to put a presence frame on the bus just to go to bed again. :)

Another option I’m looking at is that “maybe” there’s a way to put STM32 into a mode where it’s “asleep” but CAN peripheral is still working.

More to come, stay tuned...