### Q

I can't find the parameter about the maximum frequency of the input signal atthe VIN Pin. Would you please give me some advices?

### A

The 7740 uses a sigma-delta type architecture. The input goes into a switchedcapacitor integrator and then to a comparator. The 7740 output is essentially

the comparator output. The 7740 has minimal effect on the filter response - the

switched cap circuit has a low-pass filtering effect - about 6dB down at Fclk/2

- but has negligible effect at lower frequencies.

The system response will be dominated by what comes after the 7740.

Most applications would involve counting 1's on the output of the 7740 to

determine the frequency, possibly to turn the VFC into an ADC type function.

This counting process is an averaging step, and will low-pass-filter the 7740

output. The low pass filter cutoff will depend on the average size, which will

in turn determine the resolution, but would typically be 1000 times less than

the Fclk. This frequency response will have a far greater effect than the 7740

itself.