LMC567

The LMC567 low power tone decoder can be operated at supply voltages of 2V to 9V and at input frequencies ranging from 1 Hz up to 500 kHz.

The LMC567 can be directly substituted in most LM567 applications with the following provisions:
1. Oscillator timing capacitor Ct must be halved to double the oscillator frequency relative to the input frequency (See OSCILLATOR TIMING COMPONENTS).
2. Filter capacitors C1 and C2 must be reduced by a factor of 8 to maintain the same filter time constants.
3. The output current demanded of pin 8 must be limited to the specified capability of the LMC567.

The LMC567 is a low power general purpose LMCMOS™ tone decoder which is functionally similar to the industry standard LM567. It consists of a twice frequency voltage-controlled oscillator (VCO) and quadrature dividers which establish the reference signals for phase and amplitude detectors. The phase detector and VCO form a phase-locked loop (PLL) which locks to an input signal frequency which is within the control range of the VCO. When the PLL is locked and the input signal amplitude exceeds an internally pre-set threshold, a switch to ground is activated on the output pin. External components set up the oscillator to run at twice the input frequency and determine the phase and amplitude filter time constants.