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How to calculate average current for "hibernate mode"+"Active" | Cypress Semiconductor

How to calculate average current for "hibernate mode"+"Active"

Summary: 18 Replies, Latest post by danaaknight on 08 Dec 2014 12:31 PM PST
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Hakob_1981's picture
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40 posts
Hello to everybody, I have read the "PSoC® 5LP: CY8C56LP Family
Datasheet" and found:
Current in Active mode 3.1mA, Hibernate 300nA, Wakeup Time <200 µs.
I need to calculate average current if will exist wakeup for 10 nSec during each 10mS.
(I hope it will not higer than 500-700nA)
So for calculating this average current I need to know current during wakeup time (<200 µs).
I can not find it in datasheet.
 
Regards,
Hakob
user_1377889's picture
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10803 posts

Let's do a worst-case calculation with your given data. When the wakup uses as much as the running state we have got

3.1 mA * 210ms = 651 mA ms = 0,651 mAs = 651 nAs. So your average will be 651 nA.

 

Bob

user_1377889's picture
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10803 posts

Don't you think that 10ns is a bit too short to wakup your devices that you have sent to sleep and again prepare ti sleep? Or are you talking about you will do the job after wakeup in 1 ms ?

 

Bob

Hakob_1981's picture
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40 posts

 Dear Bob

let's think the device will sleep 10 millisecond , will work during 0.1 millisecond and wakeup time is 200 microsecond=0.2 millisecond,

will the calculation S_all = (S1+S2+S3), and  I_average = (S1+S2+S3)/(1000 microsec.+200 microsec + 10 microsec) where

S1 = 0.3*1000 mA*microsec, S2+S3= 210*3.1 mA*microsec. (as you said for worst case), we will have 

I_average = (0.3*1000+210*3.1)/1210 mA = ~ 0.785 mA = 785 microA  ?

 

user_1377889's picture
User
10803 posts

Charge consumed will be

Sum(tn * In) so we will have

S1 * I1 + S2 * I2 + S3 * I3 = 1000µs * 300nA + 200µs * 3.1mA + 10µs * 3.1mA

= 0,3mAµs + 620mAµs + 31mAµs

= 651,3mAµs

= 651.3nAs

which will be a current of 651.3nA every second. Or am I wrong?

 

Bob

user_14586677's picture
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7648 posts

This might be useful -

 

www.cypress.com/

 

Regards, Dana.

Hakob_1981's picture
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40 posts

 I think 651,3mAµs is the area for all one complete cycle and the current will

651.3/1210 = ~0.538 mA = 538 µA, (1210 is one cycle's duration ),
so the current depend generally from wakeup time + working time , if you want to decrease it you have to decrease those intervals.  That is why I need to know current during wakeup time.
 
regards,
Hakob  
user_1377889's picture
User
10803 posts

10 ms are not 1000µs, but 10000µs!

 

Bob

 

user_14586677's picture
User
7648 posts

If you want a more accurate calculation newer DSOs can capture a complete

cycle, measure, and perform all the calculations for you. This ap note, although

Bluetooth, shows / captures the "real" startup and operating and shutdown

consumption. The newer DSOs will do all the calcs for you on these waveforms.

 

www.google.com/url

 

Regards, Dana.

Hakob_1981's picture
User
40 posts

 Right, 10 ms are 10000µs and average current will ~53.8 µA, which is 10 times higher than expected.

Dear danaaknight I saw content from "www.google.com/url", our calculation same with their.

Now the problem is to know how much current will go during wakeup .

regards,

Hakob

user_1377889's picture
User
10803 posts

What makes you think that the wakeup current is higher than the max. current of 3.1 mA?

 

Bob

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