AVR-Chat

The word "across" in your message I quoted means something to me.
Big or Small doesn't make a difference (still LPF, better or worse).

----- Original Message ----- 
From: <dlc@frii.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Tuesday, June 19, 2007 9:16 AM
Subject: Re: [AVR-Chat] Using the ADC to measure the battery supply?


>> I'm also curious, but a cap IS a low pass filter.
>
> Depends, series or shunt?  Big cap or small?
>
> DLC
>
>> Cat
>> ----- Original Message -----
>> From: "dlc" <dlc@frii.com>
>> To: <AVR-Chat@yahoogroups.com>
>> Sent: Monday, June 18, 2007 11:00 PM
>> Subject: Re: [AVR-Chat] Using the ADC to measure the battery supply?
>>
>>
>>> If the cap is across it then the ADC might not get the correct voltage
>>> either.  The ADC relies upon charging a cap inside the module.  That
>>> relies upon a certain target RC charge rate, that charge rate also must
>>> not exceed the current capacity of the pin.  You are playing a finicky
>>> game by using a cap to boost the inrush current to offset the RC time
>>> constant.  It might work under some circumstances but since the ADC
>>> modules specifically states that you should only be using slowly
>>> changing signals on the circuit with low-pass filters that would tend to
>>> contra indicate using a bypass cap I think.  Have you used such a
>>> circuit successfully before?
>>>
>>> curious,
>>> DLC
>>>
>>>
>>
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