LMC567CMX

Telecom Overview

The LMC567CMX is a low-power tone decoder manufactured by Texas Instruments, functionally similar to the industry-standard LM567. It operates on a supply voltage range of 2V to 9V with a maximum input frequency of 500 kHz. The device features an internal phase-locked loop (PLL) and a voltage-controlled oscillator (VCO) that runs at twice the input frequency. Key electrical parameters include a quiescent supply current of 0.3 mA at 2V and 0.8 mA at 9V. The output pin provides a ground-referenced switch with a 20 mA capability. The center frequency shift with supply voltage is typically 2.0 %/V, and the largest detection bandwidth ranges from 11% to 17% depending on the supply voltage.

Telecom Feature Summary

• Low power consumption with no increase in supply current when the output switch is activated
• Internal phase-locked loop establishes reference signals for phase and amplitude detectors
• Ground-referenced input pin with hysteresis added to the amplitude comparator
• Capable of rejecting out-of-band signals and noise while operating up to 500 kHz

Telecom Applications

• Tone decoding in communication systems
• Frequency monitoring circuits
• Remote control decoders
• FSK demodulation applications

Telecom Procurement Notes

Verify the package type matches the required PCB footprint, as the CMX suffix indicates a surface-mount Small Outline Package. Confirm the manufacturer origin, noting that National Semiconductor was acquired by Texas Instruments, which may affect documentation sources. Ensure the ordering number corresponds to the specific tape-and-reel quantity if applicable for automated assembly processes.

Telecom Selection Notes

Select this component when a low-power CMOS alternative to the bipolar LM567 is required. Note that external timing capacitors must be halved compared to LM567 designs to maintain the correct VCO frequency relationship. Ensure the application does not require output currents exceeding the specified 20 mA limit, as the internal FET switch has limited drive capability compared to bipolar counterparts.

Telecom Part Context

The LMC567 belongs to the family of general-purpose tone decoders based on LMCMOS technology. It serves as a direct functional replacement for the LM567 in most applications, offering lower power dissipation. The device integrates a quadrature divider and phase detector within a single monolithic circuit, simplifying the design of PLL-based frequency detection systems.

Telecom Replacement Considerations

LMC567CM

Telecom FAQ

How does the oscillator timing differ between LMC567 and LM567?

The LMC567 VCO must run at twice the input frequency. Consequently, the oscillator timing capacitor (Ct) must be halved compared to LM567 designs to achieve the same center frequency.

What is the input impedance of the LMC567?

The input pin (Pin 3) is internally ground-referenced with a nominal resistance of 40 kΩ.

Can multiple LMC567 devices share a common input signal?

Yes, inputs of multiple LMC567 devices can be paralleled without individual DC isolation, provided the signals are centered on 0V or isolated via coupling capacitors.