Hi All,
I wondered if you could provide some advice with regards to a filter I am designing for the output of an analogue sensor that outputs a voltage between 0V and 5V I then need to step this down to 3V3, but I am only interested in frequencies up to and including 72kHz anything above this I want to reject, because this signal is also used for control feedback I also need to reduce the phase ( less than or equal to 10 degrees). At the moment attached is what I have done just a potential divider with a capacitor, if anyone could suggest anything that would perform any better.

Kind Regards

Art

 

In general you can't readily filter a signal without a time delay or phase shift.
If the signal is used in a feedback control system, then you will need to take the filter phase-shift into account when designing the feedback loop response.

 

There is a whole class of filters called "minimum phase" that are used in
DSP based systems. Lots of info on web.

However I cannot tell from your limited description of the design problem
weather or not this is even necessary or needed, eg. a DSP approach.

Regards, Dana.

 

There is a whole class of filters called "minimum phase" that are used in
DSP based systems. Lots of info on web.

However I cannot tell from your limited description of the design problem
weather or not this is even necessary or needed, eg. a DSP approach.

Regards, Dana.

Hi thanks for the suggestion I am designing a DC-DC Converter this is one of the feedback properties in the control for this converter

 

Unless your goal is to design it yourself, there are lots and lots of DC-DC controller ICs on Digikey, Mouser, etc..

 

Normally in a control loop one wants phase margin, or to minimize phase shift
when the gain crosses 0 db for stability.

Specifics here -

https://www.allaboutcircuits.com/te...feedback-part-5-gain-margin-and-phase-margin/


Regards, Dana.

 

A DC to DC converter is some form of switching mode power supply and those are complicated because not only is the circuit and component values a challenge, but even the circuit layout matters a lot at those power and frequency ranges. There are lots of design assistance programs available and also a whole lot of products around. So unless you are planning on producing a large number of them, my suggestion is to buy something already existing from the large range of available products.

 

Normally in a control loop one wants phase margin, or to minimize phase shift
when the gain crosses 0 db for stability.

Specifics here -

https://www.allaboutcircuits.com/te...feedback-part-5-gain-margin-and-phase-margin/


Regards, Dana.

Thanks so much for this resource really appreciate it

 

In a switching mode power supply there is far more to stability than just the output filtering. Almost evey conductor on the circuit board has the potential of affecting the feedback. This means that making such a supply is a real challenge.

 

Some ref material -

https://www.analog.com/media/en/technical-documentation/application-notes/AN149fa.pdf

https://www.edn.com/design/power-ma...sign-of-Switching-Mode-Power-Supplies--Part-1

http://www.ti.com/lit/an/slva633/slva633.pdf


Regards, Dana.

 

Some ref material -

https://www.analog.com/media/en/technical-documentation/application-notes/AN149fa.pdf

https://www.edn.com/design/power-ma...sign-of-Switching-Mode-Power-Supplies--Part-1

http://www.ti.com/lit/an/slva633/slva633.pdf


Regards, Dana.

Certainly, because making such a supply work well is not simple, there are websites that offer a great deal of help.

 

Some ref material -

https://www.analog.com/media/en/technical-documentation/application-notes/AN149fa.pdf

https://www.edn.com/design/power-ma...sign-of-Switching-Mode-Power-Supplies--Part-1

http://www.ti.com/lit/an/slva633/slva633.pdf


Regards, Dana.

Thank so much Dana appreciate it, I am not so similar with feedback loops for SMPS so really appreciate it