DESCRIPTION
The NE568A is function and pin-compatible with the NE568, requiring only minor changes in peripheral circuitry (see Figure 3). Temperature compensation network is different, no resistor on Pin 12, needs to be grounded and Pin 13 has a 3.9kΩ resistor to ground. Timing cap, C2, is different and for 70MHz operation with temperature compensation network should be 16pF, not 34pF as was used in the NE568. The integrated circuit consists of a limiting amplifier, a current-controlled oscillator (ICO), a phase detector, a level shift circuit, V/I and I/V converters, an output buffer, and bias circuitry with temperature and frequency compensating characteristics. The design of the NE568A is particularly well-suited for demodulation of FM signals with extremely large deviation in systems which require a highly linear output. In satellite receiver applications with a 70MHz IF, the NE568A will demodulate ±20% deviations with less than 1.0% typical non-linearity. In addition to high linearity, the circuit has a loop filter which can be configured with series or shunt elements to optimize loop dynamic performance.
Philips
