I am working on a circuit it should have 3 input signal types (should be measurable at the same time) and i need to detect their ON-OFF times, the input voltages may range between 0.5V - 40V
something like,
1. pwm motor control
2. frequency convertors
3. relay contacts

the circuit will have an Xmega to do the processing, As my safety elements i am using TVS diodes to limit the voltage upto 40V, and i'm thinking about using SC-filters to do some processing before the data is fed to the Xmega

Kindly guide me about any alternate options for how to work with these requirements. I have some data regarding the specifications, in case of any questions or suggestions i am not able to understand i will consult with my supervisor.

 

break it down into smaller, manageable tasks and execute them one at a time. i would start with specs such as voltage (already mentioned), frequency range, input impedance etc (nor mentioned). once you know all those, you can start designing input stage...

 

break it down into smaller, manageable tasks and execute them one at a time. i would start with specs such as voltage (already mentioned), frequency range, input impedance etc (nor mentioned). once you know all those, you can start designing input stage...

this may sound like a stupid question, but can is use a voltage divider on a pwm signal ?
because my problem is the high voltage, but my primary goal is the measurement of frequency, so if i use a voltage divider on the pwm signal to bring the amplitude within the input limits of the possible ic's i want to use, things would get really easy for me.

 

It's hard to say what is reasonable because you haven't given a reasonably complete set of specs and goals.

You might be able to get by with a comparator to turn your input signal into a digital pulse train with a uniform amplitude.