The invention provides a digital modulator system for use in a fractional-N frequency synthesizer, said system comprising: a first pipelined modulator configured to receive a digital signal via a bus signal; a second pipelined modulator configured to receive a part of said digital signal; and said system is adapted to split the bus signal by passing least significant bits (LSBs) of said digital signal through the second modulator, combining the output of said second modulator with the most significant bits (MSBs) of said digital signal, and adapted to pass the combined signal through said first pipelined modulator. The combination of bus-splitting and pipelining in the modulator system is configured to provide an output signal to maximize the update rate of a multi-modulus divider of said fractional-N frequency synthesizer.