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Hot!BM64 Power issue

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gamli
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2019/08/21 00:20:31 (permalink)
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BM64 Power issue

Hello,
I have a problem with a product I am designing, and I would really appreciate some support with this problem!
I am using a BM64 module, designed into my custom system, printed on a PCB. The system streams audio via Bluetooth, communicates with an MCU using I2C and I2S, and is battery powered by a Li-Ion battery. When the battery is low (around 3.4-3.6 V which is BW 2-9% bat capacity in my case), I tend to lose the Bluetooth connection at the moment I start to stream music.
So the procedure is:
  • Power on -> battery is low
  • Pair system with a phone using BT
  • When music is started, a large current spike is detected, causing a temporary drop in the BM64 input voltage below 3.2V
  • MCU still alive but BT connection is dropped without the MCU knowing about it.
I will attach the waveform of the moment of the current spike (where the audio should start streaming but the BT connection is dropped). The yellow waveform is the total current draw of the system, where the current spike is mostly coming from the BM64, and the green waveform is the voltage input of the BM64.
 
The power supplying the BM64 comes from the battery on the BAT_IN, with two ceramic capacitors in parallel by the supply (4.7uF and 100nF). I am currently thinking of increasing the capacitance (or alternatively using tantalum caps instead) in order to avoid the problem, but it is not certain that it will be possible for this design.
 
Is there any way of decreasing this current spike using a SW configuration for the BM64?
Any recommendation/advice is really appreciated!
 
/Gamli

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#1
ryanafleming
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Re: BM64 Power issue 2019/10/31 18:56:00 (permalink)
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Since you are the only person to ever post in this forum, I don't you will ever get an answer.
 
Regardless, why not simply try putting some bulk capacitance on your board over the 4.7uF cap that exists. Simply solder a large through-hole cap in the range of 100uF just to evalute that issue?
 
This happens quite often with cellular modems that give huge current spikes in order to do data transmissions and need capacitiance in the order of 1000uF just to stay alive. Having a battery should certainly help your issue though.
#2
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