The ADF4217L/ADF4218L/ADF4219L are low power dual frequency synthesizers that can be used to implement local oscillators in the up-conversion and down-conversion sections of wireless receivers and transmitters. They can provide the LO for both the RF and IF sections. They consist of a low noise digital PFD (phase frequency detector), a precision charge pump, a programmable reference divider, programmable A and B counters, and a dual modulus prescaler (P/P + 1). The A and B counters, in conjunction with the dual modulus prescaler (P/P + 1), implement an N divider (N = BP + A). In addition, the 14-bit reference counter (R Counter) allows selectable REFIN frequencies at the PFD input. A complete PLL (phase-locked loop) can be implemented if the synthesizers are used with an external loop filter and VCOs (voltage controlled oscillators).