BETALM567Phase-locked-loop tone decoder
Recognize a tone and turn it into a clear logic signal.
LM567C uses a phase-locked loop to recognize a tone near an externally selected frequency. When a sufficiently strong signal lies inside its detection band, an internal output transistor turns on and pulls OUT low. A pull-up resistor supplies the released HIGH state. A resistor between pins 5 and 6 and a capacitor from pin 6 to ground set the nominal center frequency. Separate capacitors at pins 2 and 1 set loop filtering and output response; they do not replace the timing capacitor. This page covers the LM567CN/NOPB and LM567CM/NOPB commercial parts, rated from 0 to 70°C. The illustrated 5 V circuit uses 10 kΩ and 100 nF for approximately 909 Hz. Component tolerances, signal amplitude, filters and settling determine actual detection.
