# converting square wave into voltage using LM2907 Frequency to Voltage Converter

Sep 24, 2013
1
We have an input square wave with an amplitude of 8-9v and frequecy ranging from 0-67Hz. We are trying to convert the frequency to a voltage range of 0-3.3V with the cleanest output signal possible. We are having trouble deciding on the C1/C2/R1 values of the lm2907. The datasheet for the lm2907 is here[1] . It says the Vo range is Vo=Fin*Vcc*R1*C1. our Vcc is 10v. C2 is supposed to be for cleaning the output signal and we have at 1uF. We are having trouble determining the best C1/R1 values to get a 0-3.3v signal thats clean. For some reason with C1=1uF and R1=5k, which adds up to 3.3v at 67Hz (our max frequency), the max output voltage is only ~1.3v. It might have something to do with the max current output but we've tried all types of combinations and no dice. There are a few other equations in the datasheet but we can figure out what I2 or Ic is exactly. Can anyone help us out please. Thank you.

J
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