The LM567C is a general-purpose tone decoder designed to provide a saturated transistor switch to ground when an input signal is present within the passband. The circuit consists of an I and Q detector driven by a voltage-controlled oscillator (VCO) which determines the center frequency of the decoder. External components are used to independently set center frequency, bandwidth, and output delay.

The LM567C can be used in a variety of applications, including:

• Touch-tone dialing detection
• Remote control systems
• Industrial control systems
• Security systems
• Medical equipment

The LM567C is available in an 8-pin dual in-line package (DIP) and operates from a supply voltage of 4.75V to 9V. It has a power consumption of 1.1W and an operating temperature range of 0°C to 70°C.

Features:

• General-purpose tone decoder
• Saturated transistor switch to ground output
• I and Q detector driven by a VCO
• Independently set center frequency, bandwidth, and output delay
• Wide supply voltage range (4.75V to 9V)
• Low power consumption (1.1W)
• Wide operating temperature range (0°C to 70°C)

Applications:

• Touch-tone dialing detection
• Remote control systems
• Industrial control systems
• Security systems
• Medical equipment

Functional Description:

The LM567C tone decoder consists of an I and Q detector driven by a VCO. The I and Q detector compares the input signal to two internally generated reference signals, one of which is in phase with the input signal and the other of which is 90° out of phase with the input signal. The output of the I and Q detector is a DC voltage which is proportional to the amplitude of the input signal and the phase difference between the input signal and the reference signals.

The VCO generates a square wave signal whose frequency is determined by the external components connected to the LM567C. The output of the VCO is used to drive the I and Q detector.

When the input signal frequency matches the center frequency of the LM567C, the output of the I and Q detector is maximized. This causes the output of the LM567C to switch to ground.

The LM567C has two outputs: a logic output and a power output. The logic output is an open-collector transistor switch which requires an external load resistor to regulate the output current level. The power output is a saturated transistor switch which can be used to drive loads up to 50mA.

Setting the Center Frequency:

The center frequency of the LM567C is set by the external components connected to pins 6 and 7. The center frequency is determined by the following equation:

Fc = 1 / (2 * π * R6 * C7)

where:

• Fc is the center frequency in Hz
• R6 is the resistance of the resistor connected to pin 6 in ohms
• C7 is the capacitance of the capacitor connected to pin 7 in farads

Setting the Bandwidth:

The bandwidth of the LM567C is set by the external components connected to pins 4 and 5. The bandwidth is determined by the following equation:

BW = 1 / (2 * π * R4 * C5)

where:

• BW is the bandwidth in Hz
• R4 is the resistance of the resistor connected to pin 4 in ohms
• C5 is the capacitance of the capacitor connected to pin 5 in farads

Setting the Output Delay:

The output delay of the LM567C is set by the external components connected to pin 3. The output delay is determined by the following equation:

Output_Delay = 1 / (2 * π * R3 * C3)

where:

• Output_Delay is the output delay in seconds
• R3 is the resistance of the resistor connected to pin 3 in ohms
• C3 is the capacitance of the capacitor connected to pin 3 in farads

Conclusion:

The LM567C is a versatile tone decoder that can be used in a variety of applications. It is easy to use and configure, and it offers a wide range of features.