PWM to Analog Voltage conversion.

[Sanyam Mulay]

I checked out (experimentally) simple RC low pass filters.

Any better ideas ?

Spec. PWM - 1kHz; variable duty cycle; 3.6V peak to peak
        
        

[Kartik Mohta]

Any particular problem with the RC filter?

--
Kartik

[Siraj Issani]

On Fri, Dec 3, 2010 at 10:43 PM, Kartik Mohta <karti...@gmail.com> wrote:
> Any particular problem with the RC filter?
>

Variable duty cycle makes things a little more tricky. While designing
your filter, do not design for a cut off of 1kHz. It should be able to
let pass the small "peaks" of the signal when the duty cycle is very
low. So if the minimum duty cycle you wish to pass through the filter
is 10% then you should have a filter cut off frequency suiting a
square wave of period 2*(10% of 1/1kHz). This is vaguely what I
remember as a thumb rule from an elaborate calculation I did before
(and also posted in this forum, if you search through the archives).

--
Siraj

> On Fri, Dec 3, 2010 at 1:54 AM, Sanyam Mulay <sanyam...@gmail.com> wrote:
>> I checked out (experimentally) simple RC low pass filters.
>>
>> Any better ideas ?
>>
>> Spec. PWM - 1kHz; variable duty cycle; 3.6V peak to peak
>>
>>
>>
>
>
>
> --
> Kartik
>

--
Siraj

[Siraj Issani]

And as the undo button disappears, I read the subject more closely and
realize what I said doesn't apply to your application. Please strike
that off the record. For your application you can try out
(experimentally) an LR filter, which is commonly available as a single
component for analog signals.

--
Siraj

[Mehul Tikekar]

Why LR? I thought RC is easier to get.

Mehul

[Sanyam Mulay]

Sorry for the late reply, I was out of insti.

The only problem with simple RC is that it has some residual ripples, these should be as low as possible. 

[Siraj Issani]

Yeah, even I am curious to know why they are supposed to work better. I have seen colleagues use it on boards for rectification purposes. That's why I suggested him to try "experimentally". Awaiting formal corroboration.

-- Siraj

On Dec 5, 2010 1:14 AM, "Mehul Tikekar" <mehult...@gmail.com> wrote:

Why LR? I thought RC is easier to get.

Mehul

On Fri, Dec 3, 2010 at 11:42 PM, Siraj Issani <siraj....@gmail.com> wrote:
>

> And as the undo ...