Hi all,

I am looking for a frequency to voltage converter, I am checking the AD650 chip. This is a VFC converter but it could be used like FVC, this application is well descripted in the application note AN-279.

I have a couple of doubts:

The first is in the (3) formula on page 2 of the AN279. In this formula 'I' parameter compares, in my opinion this is not a parameter and is a division symbol '/', only in this case the dimensional analysis is right.

The second doubt is relative to the response time of the FVC. In my system this time has to be in the order of milliseconds; it seems that this time is compatible only with high ripple value.

My system frequency range is 50-120KHz, I need 1ms response time. The ADC is 12 bit precision and using a 2.048V range it can appreciate 0.5mV of variation. I could try to work using 10 bit precision, in this case my system can work with a ripple <2mV.

Did someone use this component (or similar) for similar application?

Thank you in advance and regards.

Nicola

Hi Nicola,

Looking at the application note (AN-279) I agree that in equation (3) the 'I' parameter should in fact be a division sign '/'. I will make a note of this and ensure that the application note is revised.

There is an AD650 component selection calculator located at http://designtools.analog.com/dt/v2f/ad650.html which you can use to enter your application parameters and it will determine the values of components you need to use to achieve the desired performance.

Unfortunately I am not very familiar with this part and so do not know if any of our customers are using similar criteria to your own with this particular part. However, using the AD650 as a FVC is fully supported. Let me know if you need more help.

Regards,

Rob

ADI classifies these under our ADC products rather than our clock products, so I have moved it to the appropriate forum.