10 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

10.1 Application Information

The LM567 tone decoder is a device capable of detecting if an input signal is inside a selectable range of

detection. The device has an open collector transistor output, so an external resistor is required to achieve

proper logic levels. When the input signal is inside the detection band, the device output will go to a LOW state.

The internal VCO free running frequency establishes the detection band central frequency. An external RC filter

is required to set this frequency. The bandwidth in which the device will detect the desired frequency depends

on the capacitance of loop filter terminal. Typically a 1µF capacitor is connected to this pin. The device detection

band has a different behavior for low and high input voltage levels. Refer to the Operation With Vi < 200m –

VRMS section and the Operation With Vi > 200m – VRMS section for more information.

10.2 Typical Applications

10.2.1 Touch-Tone Decoder

Component values (typ) R1 6.8 to 15k R2 4.7k R3 20k C1 0.10 mfd C2 1.0 mfd 6V C3 2.2 mfd 6V C4 250 mfd 6V

Figure 10-1. Touch-Tone Decoder

LM567, LM567C

SNOSBQ4F – MAY 1999 – REVISED JANUARY 2022

www.ti.com

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