National Semiconductor LMC568 Low Power Phase-Locked Loop Data Sheet
Summary
The LMC568 is a low-power Phase-Locked Loop (PLL) designed for highly stable demodulation of FM or FSK signals. It offers high performance up to 500 kHz while maintaining linearity and low power consumption, making it ideal for advanced consumer electronics. This manual provides comprehensive details, including electrical characteristics, absolute maximum ratings, typical application circuits, and soldering guidelines. It is specifically tailored for engineers developing applications such as FM SCA/TV audio decoders, FSK data demodulators, and voice pagers requiring reliable signal processing.
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LM Low ow er hase-Locked Loop
LMC568 Low Power Phase-Locked Loop General Description Features
The LMC568 is an amplitude-linear phase-locked loop con- Demodulates ±15% deviation FM/FSK signals
sisting of linear VCO, fully balanced phase detectors, and Carrier Detect Output with hysteresis carrier detect output. LMCMOS™ technology is employed Operation to k Hz input frequency for high performance with low power consumption. Low THD 0.5% typ. for ±10% deviation
The VCO has linearized control range of ±30% to allow de- 2V to 9V supply voltage range
modulation of FM and FSK signals. Carrier detect is indi- Low supply current drain cated when the PLL is locked to an input signal greater than m Vrms. LMC568 applications include FM SCA and TV second audio program decoders, FSK data demodulators, and voice pagers.
Typical Application (100 k Hz input frequency, refer to notes pg. 3)
DS009135-1
Order Number LMC568CM or LMC568CN See NS Package Number M08A or N08E
LMCMOS™ is trademark of National Semiconductor Corporation.
National Semiconductor Corporation DS009135 www.national.com
Page Summary Contents For National Semiconductor LMC568 Low Power Phase-Locked Loop Data Sheet
Manual Details
| Brand | National |
|---|---|
| Pages | 6 |
| File Size | 162.56 KB |
| Published | June 17, 2026 |
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Frequently Asked Questions
What types of signals can the LMC568 demodule?
It demodulates ±15% deviation FM/FSK signals, suitable for applications like SCA and TV second audio program decoders.
What is the typical total harmonic distortion (THD)?
The THD is typically 0.5% when measuring a 10% deviation input signal.
What are the supply voltage limits for operation?
The chip can operate within a power supply range of 2V to 9V and has maximum absolute ratings up to 13V on Pin 8.
What is necessary care when designing the circuit?
Supply decoupling, particularly for Pin 4, is critical. A large capacitor (C4) placed close to Pin 4 is recommended for optimal performance.