Datasheet

© 2007 Microchip Technology Inc. DS21483D-page 13
TC9400/9401/9402
5.0 FREQUENCY-TO-VOLTAGE
(F/V) CIRCUIT DESCRIPTION
When used as an F/V converter, the TC9400 generates
an output voltage linearly proportional to the input
frequency waveform.
Each zero crossing at the threshold detector’s input
causes a precise amount of charge (q = C
REF
x V
REF
)
to be dispensed into the op amp’s summing junction.
This charge, in turn, flows through the feedback
resistor, generating voltage pulses at the output of the
op amp. A capacitor (C
INT
) across R
INT
averages these
pulses into a DC voltage, which is linearly proportional
to the input frequency.