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Wi-Fi Combo Forum Discussions

janvc_4048556
Level 1
Level 1

Hi,

I hope this is the right place to post this question.

We are using an embedded BCM43438 chip for wifi communication on a board powered by single 1 cell LIPO battery.

When wifi is activated we exprience periodic powe consumption spikes (which cause a reset to our CPU when battery levels start to drop).

The period depends on whether we connected to the required network or not.

When we are connected this happens roughly every 2 minutes, otherwise its about 6 seconds.

We would like to know what is happening and whether we can disable it or not.

The current draw is much higher than normal transmission power and even much more than when we initiate a scan (i.e. iwlist scan)/

I would really appreciate any help on this issue,

Thank you very much

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1 Solution

Hello:

    For 43438 chip, we actually didn't meet the issue like mentioned above, the current is acting like spec describes.

better to change or check the circuit or module with the vendor,  thanks.

View solution in original post

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13 Replies
ChMa_3922746
Level 5
Level 5
10 likes received 10 likes given 5 likes given

Do you know the internal resistance and max. current that the battery can deliver (per the datasheet)?  Compare that to the current draw you are measuring (are you using a scope across a sense resistor)?

Thank you for your reply,

I do not know the internal resistance of the battery, but the current draw is more than it can take (its a 250mah 1C LIPO). How ever I do not expect the WIFI chip to draw that much current at any case

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So only wifi is using TX side , the current will be much higher than normal value. My suggestions are:

1. try to change another chip or module to compare.

2.  check the PA related Voltage circuit since 43438 should use an internal PA.

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Hi.

unfortunately I can not use another chip, I'm using an evaluation kit.

I'm sorry I failed to mention that, it's the "Newton 2 plus" kit by Ingenic.

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hello:

Do you have Ingenic spec for the evb ?  I think you can get the normal value from the document, then raise help to the support.

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I do not have the spec (only a HW dev guide in Chinese), However we do not expect peak current to be more than ~350mA.

The following figure is a snapshot taken with our scope.

Each square is 20mV which is equivalent to 200mA, you should also note that the measurement is upside down.

As seen, on normal terms the board consumption ranges around 50mA, the phenomena that begins at the 3rd square demonstrates the same pattern at all the cases I mentioned (1. Immediately after WIFI activation, 2. periodically every 6 secs or 2 minutes) . The lower spikes are around 200mA and the highest spike (which causes the reset) is around 800mA.

Any insight on the disabling the high 800mA spike would help (even if we just disable the periodic cases)

current_1.jpg

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Hi, I got the data now, internal resistance is 100mOhm

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That's an 80mV drop out of the battery at peak current.  I would contact Ingenic and for the max. current draw. 

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hello:

   Would you please share the current status for this peak current issue ? thanks.

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Sadly I have not been able to make any progress on that issue

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Hello:

    For 43438 chip, we actually didn't meet the issue like mentioned above, the current is acting like spec describes.

better to change or check the circuit or module with the vendor,  thanks.

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Zhengbao_Zhang
Moderator
Moderator
Moderator
First comment on KBA 10 questions asked 5 questions asked

hello:

     If the pulse is regular, It looks like a STA wake up interval that should be a multiple of DTIM.  But that should be a normal packet up with a normal power output value .

" The current draw is much higher than normal transmission power"  ,  This is very strange .

Did you try to just measure the current consume in 43438 V_bat input pin ?  not to measure the entire board current consume.

Thank you for your replay,

Currently I can not measure it on the V_Bat pin, I measure with a scope (current probe) on the battery line itself, it seems that the delta is more than 800ma. It seems that during regular TX, increase in current draw is ~50ma, during a scan its multiple spikes of ~200ma.

The huge draw also occurs when I first enable wifi.

I am positive that the wifi chip is the cause, as when I disable wifi (through standard linux commands) the phenomena stops.

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