Measuring current for AN92854 Low power apps TOO MUCH Current

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
Anonymous
Not applicable

Hi,

   

     I am using the BlueTooth Pioneer kit with the PSoC 4 board and using the AN92854 application note.  I am running the BLE_CapSense project and not getting anything near the current predicted.  I do  not have an aperture type DVM.  I have a 10Ω resistor across J15 and have a scope and the DVM across it.  Both reading mV.  The DVM averages the current to board and would represent the load seen by a batter.  We have capacitors in the CKT to handle the BLE transmissions but the average current with give us ~ battery life.  

   

     With the application running (and seen by CySmart) using 4000 ms advertisements, I see about 9.3 mV across the resistor or 0.93 ma. I can see the advertisement current spikes on the scope But the average current is the problem, it is nowhere close to the < 10 µ amp shown in the appnote.  

   

     Is this what I should expect for the average current in this application ? On the scope I see the advertisement for about 6.4 ms spaced at 4 second intervals.  I has a peak of about 500 mv or 50 mA.  

   

     The hardware we want to build with this, we hope to run from a 2032 cell (240 mAh) for 6 months for a year.  Am I totally wrong in measuring it this way ?

   

Thanks for the help.

   

--jim schimpf

0 Likes
1 Solution
manusharian
Level 4
Level 4
25 replies posted 10 replies posted 10 questions asked

Hello Jim,

   

I did some measurements too using 2 methods, one described by you and another by simply using a digital ammeter in series with J15. Of course the second method will average the current and more precised measurements should be done with you method!

   

 I can confirm your findings but to be honest a spike of 50 mA is why to much. I have about 193-200 mV using a resistor of 20 Ohms and a clock frequency of 32 MHz, which is about 10 mA. I also suppose that with a clock at 48 MHz( if this is also intended by you to use) the spike will note overcome 14-15 mA, since the clock for BLE is at 24 MHz.

   

I also used other lets call them benchmarks, where I have analyzed the power consumed by executing only asm code removing all other components for a design, and also using simple BLE application just for advertising, sending, notification, keeping the connected link etc. using the same Application Note AN92584 and after my results on a simple project I can tell you that with a 250 mAh you will have the battery for about 4 days, if my measurements are correct. I still have to test more the system and to remove more unused clocks and other parts in order to obtain better results.

   

Hopefully this helps.

View solution in original post

0 Likes
6 Replies
rola_264706
Level 8
Level 8
50 likes received 25 likes received 10 likes received
        Jim please post your program as I can't find the ap note you referenced.   
0 Likes
lock attach
Attachments are accessible only for community members.
Anonymous
Not applicable

whooops AP92584. and enclosed is the program.

   

Thanks. 

0 Likes
Anonymous
Not applicable

Hi, 

   

I am facing similar situation. So, have you solved with the problem, Jim?

   

 

   

Regards, 

   

Daryanto

0 Likes
Anonymous
Not applicable

No but now I have adapted the code from AN92584 and it is better ~0.200 µamps.

   

--jim

0 Likes
Anonymous
Not applicable

So you just used the code from that appnote, but the measurement procedure is still the same? using oscilloscope?

   

thanks

regards, 

   

Daryanto

0 Likes
manusharian
Level 4
Level 4
25 replies posted 10 replies posted 10 questions asked

Hello Jim,

   

I did some measurements too using 2 methods, one described by you and another by simply using a digital ammeter in series with J15. Of course the second method will average the current and more precised measurements should be done with you method!

   

 I can confirm your findings but to be honest a spike of 50 mA is why to much. I have about 193-200 mV using a resistor of 20 Ohms and a clock frequency of 32 MHz, which is about 10 mA. I also suppose that with a clock at 48 MHz( if this is also intended by you to use) the spike will note overcome 14-15 mA, since the clock for BLE is at 24 MHz.

   

I also used other lets call them benchmarks, where I have analyzed the power consumed by executing only asm code removing all other components for a design, and also using simple BLE application just for advertising, sending, notification, keeping the connected link etc. using the same Application Note AN92584 and after my results on a simple project I can tell you that with a 250 mAh you will have the battery for about 4 days, if my measurements are correct. I still have to test more the system and to remove more unused clocks and other parts in order to obtain better results.

   

Hopefully this helps.

0 Likes