ADF4193

The ADF4193 frequency synthesizer can be used to implement local oscillators in the upconversion and downconversion sections of wireless receivers and transmitters. Its architecture is specifically designed to meet the GSM/EDGE lock time requirements for base stations. ADF4193 consists of a low noise, digital phase frequency detector (PFD), and a precision differential charge pump. There is also a differential amplifier to convert the differential charge pump output to a single-ended voltage for the external voltage controlled oscillator (VCO).

The - based fractional interpolator, working with the N divider, allow programmable modulus fractional-N division. Additionally, the 4-bit reference (R) counter and on-chip frequency doubler allow selectable reference signal (REFIN) frequencies at the PFD input. A complete phase-locked loop (PLL) can be implemented if the synthesizer is used with an external loop filter and a VCO. The switching architecture of ADF4193 ensures that the PLL settles inside the GSM time slot guard period, removing the need for a second PLL and associated isolation switches. This decreases cost, complexity, PCB area, shielding, and characterization on previous ping-pong GSM PLL architectures.