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The MC12181 is a monolithic bipolar synthesizer integrating a high performance prescaler, programmable divider, phase/frequency detector, charge pump, and reference oscillator/buffer functions. The device is capable of synthesizing a signal which is 25 to 40 times the input reference signal. The device has a 4–bit parallel interface to set the proper total multiplication which can range from 25 to 40. When combined with an external passive loop filter and VCO, the MC12181 serves as a complete PLL subsystem.
&127; 2.7 to 5.5 V Operation
&127; Low power supply current of 4.25 mA typical
&127; On chip reference oscillator/buffer supporting wide frequency operating range from 5 to 25 MHz
&127; 4–bit parallel interface for programming divider (N = 25 .... 40)
&127; Wide 125 – 1000 MHz frequency of operation
&127; Digital phase/frequency detector with linear transfer function
&127; Balanced Charge Pump Output
&127; Space efficient 16 lead SOIC package
&127; Operating Temperature Range of –40 to 85C
&127; > 1000 V ESD Protection (I/O to Ground, I/O to V CC )
The device is suitable for applications where a fixed local oscillator (LO) needs to be synthesized or where a limited number of LO frequencies need to be generated. The device also has auxiliary open emitter outputs (Pout and Rout) for observing the inputs to the phase detector for verification purposes. In normal use the pins should be left open. The Reset input is normally LOW. When this input is placed in the HIGH state the reference prescaler is reset and the charge pump output (Do) is placed in the OFF state.
The 4–bit programming interface maps into divider states ranging from 25 to 40. A is the LSB and D is the MSB. The data inputs (A,B,C, and D) are CMOS compatible and have pull–up resistors. The inputs can be tied directly to Vcc or Ground for programming or can be interfaced to an external data latch/register.

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