LMC567

Low Power Tone Decoder

General Description

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 ampli-

tude detectors. The phase detector and VCO form a

phase-locked loop (PLL) which locks to an input signal fre-

quency 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.

Features

n Functionally similar to LM567

n 2V to 9V supply voltage range

n Low supply current drain

n No increase in current with output activated

n Operates to 500 kHz input frequency

n High oscillator stability

n Ground-referenced input

n Hysteresis added to amplitude comparator

n Out-of-band signals and noise rejected

n 20 mA output current capability

DS008670-1

Order Number LMC567CM or LMC567CN

See NS Package Number M08A or N08E

June 1999

© 1999 National Semiconductor Corporation

DS008670

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