The MC1648 requires an external parallel tank circuit consisting of the inductor (L) and capacitor (C). For Maximum Performance QL ≥ 100 at Frequency of Operation.

A varactor diode may be incorporated into the tank circuit to provide a voltage variable input for the oscillator (VCO). The MC1648 was designed for use in the Motorola Phase–Locked Loop shown in Figure 9. This device may also be used in many other applications requiring a fixed or variable frequency clock source of high spectral purity. (See Figure 2) The MC1648 may be operated from a +5.0Vdc supply or a –5.2Vdc supply, depending upon system requirements.