Frequency to voltage converter to 30MHz (simple)

[neazoi]

AD650 seems a good solution but it is only suited to 1MHz.
Any other solutions?

 

[Surendhar M]

It is better to design by your own instead of going for an IC for 30MHz. I don't think that you will be able to find it out easily when you started looking for a part.

 

[BradtheRad]

Here is what could be called simple.

A high-pass filter. The higher the frequency, the greater the amplitude,



Values must be adjusted until you find a range of linear response.

The peak detector requires a diode suitable for the fast frequency.

 

[D.A.(Tony)Stewart]

Basically a Tachometer is a 1shot per cycle averaged into a Low Pass Filter.

0 to 30MHz would require a 1/30 us 1-shot or 33ns or less.

The unknown part is your spec for the input waveform, as errors can occur with any F2V convertor unless the input has well defined constraints. such as harmonics, noise, amplitude sensitivity, slew rate input range Vpp and maximum noise.

WIth these types of constraints you can define the best solution with a simple diode detector, ECL slicer or Linear comparator, or similar such limiter to trigger a fixed charge into a bigger capacitor and take the average voltage.. THese choices also affect the lower freq limit.

If you need response to 1kHz the design would look different and requires over 3 decades of linearity and SNR in the output.

The purpose of F2V converter is a simple tach. Complex ones with narrow band use linear PLL's

I once designed a 10Mbps SCADA system which also had some DC drive motors with current sensing.
I had no more Digital channels to support the data, since it was low bandwidth, I used a spare bit in a signalling channel as a one shot from 0 to 1KHz. So the DC was converted to F as a 1 shot using a S/R latch to send a "1" bit only once per input signal cycle and then regenerating the 1-shot at the Receiver console to display the motor current on an Analog Panel Meter. ( circa '77)