![]() This signal is sent to the quadrature phase detector together with the signal input at pin ③ for comparison. ![]() When the tone decoder LM567 works, its phase-locked loop internal current-controlled oscillator generates an oscillation signal of a certain frequency and phase. Top View of LM567 III LM567 Working Principle & Application The capacitor connected to pin ② determines the capture bandwidth. The larger the value of the capacitor, the narrower the loop bandwidth is.įigure 2. The external resistance and capacitance of pins ⑤ and ⑥ determine the center frequency f 0≈1/1.1RC of IC internal voltage controlled oscillator. Pins ① and ② are usually connected to the ground separately to form an output filter network and a loop low-pass filter network. It can be seen from the figure that it is an open collector transistor output, which allows a maximum sink current of 100 mA. The pin ③ is the signal input terminal, which requires the input signal to be greater than 2 5 mV. The operating voltage range of LM567 is 4.75 - 9V, the operating frequency can reach 500 KHz, and the static operating current is only 8 mA. ![]() Its internal circuit structure is composed of quadrature phase, detector, phase-locked loop, amplifier, etc. The name of LM567 is "phase-locked loop tone decoder", its package form uses 8-pin dual in-line, its internal structure and pin functions are illustrated in Figure 2. III LM567 Working Principle & Application II LM567 Internal Structure & Pin Function This blog introduces the working principle and tips about how to use LM567 tone decoder for readers' reference. However, if using improperly, it will bring troubles in debugging. It is compact in design, simple in circuit, and has a wide range of applications. LM567 is a tone decoding phase-locked loop integrated circuit.
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