AK1543

The AK1543 is a 400MHz to 1300MHz band PLL (phase locked loop) frequency synthesizer with frequency switching function by delta-sigma modulation type fractional-N. 
The AK1543 consists of an 18-bit delta-sigma modulator, a low-noise phase frequency comparator, a precision charge pump, a reference divider, and a dual modulus prescaler (P / P + 1).
The AK1543 achieves a complete PLL by combining a synthesizer with an external loop filter and a voltage controlled oscillator (VCO).