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Helpful ReplyHot!use of brown-out reset (BOR)

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soleil_sword
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2019/07/21 18:50:17 (permalink)
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use of brown-out reset (BOR)

I'm currently working on a battery powered system using MCU PIC24FJ64GA702. This MCU has a default BOR threshold voltage of ~ 2.1 V. Due to the design of my system + the characteristics of the battery, during the system operation the voltage will have a drop of about 0.1 V for a very short period of time. For example, when the voltage of the battery decreased to 2.2 V, the voltage of system will drop to 2.1 V for a very short period and trigger the BOR.
 
I don't understand the purpose of having the BOR, could someone please explain me that?
If I disable the BOR, I will not hit the BOR and therefore have a longer life of the system using the battery, is there going to be problem because of that?
What can I do with the BOR flag? 
#1
jtemples
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Re: use of brown-out reset (BOR) 2019/07/21 18:53:19 (permalink) ☄ Helpfulby soleil_sword 2019/07/21 19:02:20
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If you try to operate the PIC below its minimum Vdd, it will have undefined behavior (i.e., anything can happen).  That is why there is BOR.
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NKurzman
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Re: use of brown-out reset (BOR) 2019/07/21 18:57:03 (permalink) ☄ Helpfulby soleil_sword 2019/07/21 19:02:27
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Anything typical includes freezing up, improper execution of opcodes, which can cause the processor to run away.
Improper voltage levels output, Or incorrectly read on an input.
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ric
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Re: use of brown-out reset (BOR) 2019/07/21 18:58:50 (permalink) ☄ Helpfulby soleil_sword 2019/07/21 19:02:34
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What do you call "a very short period of time" ?
Would extra capacitance on Vdd help?
The whole point of the BOR is to stop your PIC running when the voltage is below the minimum point at which it will run reliably. It's your choice if you want to disable it and push the limit.
(The datasheet already warns that analog performance will be degraded below 2.2V)
 

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soleil_sword
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Re: use of brown-out reset (BOR) 2019/07/21 19:03:45 (permalink)
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ric
What do you call "a very short period of time" ?
Would extra capacitance on Vdd help?
The whole point of the BOR is to stop your PIC running when the voltage is below the minimum point at which it will run reliably. It's your choice if you want to disable it and push the limit.
(The datasheet already warns that analog performance will be degraded below 2.2V)
 


It is about 1 us of voltage drop of 0.1 V. I have already added 200 uF capacitor on the VDD to decrease the original 0.6 V drop to 0.1 V due to the system design.
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