Current peaks in Slow Idle mode


#1

Hello there,

I am developing an application on a Starter Kit with a Q2406B module. When I swicth to Slow Idle mode I can see that the power consumption of the kit falls to less than 10 mA, it varies a bit. But every few seconds the consumption peaks to a higher value, sometimes 10 mA and sometimes even 30 mA. This happens even when the application is not running.

Does someone know what the reason of these peaks is? Are they caused by the Wismo module or by something else on the Starter Kit’s motherboard?

Thanks in advance,

Bart.


#2

Hello,

There are running applications on the phone without the user open at application. If your module is registered to network, there is a lot of traffic over the GSM control channels, for example cell update, which could rise the consumption temporarily, so that peaks are normal. Simply deregister from the network, and you will not see those peaks. Please note that the voltage level converter IC on the UART has massive power consumption.

Best Regards,

tom


#3

Hello Tom,

Even when unregistered I see peaks to 26 mA about every 5 seconds. I already noticed that unplugging the COM connector reduces power comsumption but peaks still appear.

In an application note named “Power Consumption Modes” (Revision: 004
Date: September 2005) I read that the average power consumption in Slow Idle Mode should be 2.5 … 5.5 mA. Is this still true when the module is registered to the network and the data traffic is causing peaks?

Hope you can help me with this.

Kind regards,

Bart.


#4

Hi Bart,

even when not registered or without a SIM card, the module will do GSM communication. In these cases you would still be able to send an SOS call (e.g. 112 in Europe). So there will be always some traffic with the network.

Also, if the network is weak or you did not connect an antenna, I would expect to see higher current peaks than in cases with good network coverage and antenna…

Best Regards,
Jan


#5

Hello,

Maybe even with the peaks your avarage cunsumption is still between 2.5 and 5.5 mA? Could you measure that?

Jan is right, even without registration GSM traffic could happen. You can try to stop the GSM stack with AT+CPOF or try the slow or fast standby mode (in this case the GSM is off theoretically). Please write down your experiences.

Best Regards,

tom


#6

Hello all,

Does this mean that the specifications (2.5 mA or 5.5 mA) in the application note mentioned above cannot be guaranteed?

Thanks in advance,

Bart.


#7

Hello all,

Sorry, I posted my previous message before I read Tom’s.

After AT+CPOF peaks still occur but now to 8 mA.

Unfortunately I am not able to measure the average power consumption.

Regards,

Bart


#8

Those figures are averages - the whole point of an average is that it accounts for the value sometimes being higher, and sometimes lower.
If the peaks are very narrow, they can be very much greater!

That’s the way averages work!


#9

Yes, I know what average means. Thank you.


#10

Hello,

Our APN told me that this traffic happens much less than the peaks I occur.

They also wondered if the peaks could be caused by the intern LED of the modem. I checked GPIO1 but the flashing of the LED is really different from the peaks. So it does not look like this is the problem. Just to be sure I was wondering if it is possible to turn off the LED.

Thanks in advance,

Bart.