The DS8907 is a PLL synthesizer designed specifically for use in AM FM radios It contains the reference oscillator a phase comparator a charge pump a 120 MHz ECL I2L dual modulus programmable divider and an 18-bit shift register latch for serial data entry The device is designed to operate with a serial data controller generating the necessary division codes for each frequency and logic state information for radio function inputs outputs The Colpitts reference oscillator for the PLL operates at 4 MHz A chain of dividers is used to generate a 500 kHz clock signal for the external controller Additional dividers generate a 25 kHz reference signal for FM and a 10 kHz reference signal for AM One of these reference signals is selected by the data from the controller for use by the phase comparator