TRF2020

The Texas Instruments (TI) TRF2020 is an integrated high performance frequency synthe- sizer device. The TRF2020 consists of one main 1.2-GHz synthesizer and two auxiliary 250-MHz synthesizers. Each synthesizer has an independent dual-modulus prescaler and separate powerdown modes.These features provide maximum flexibility for the design of 900-MHz wireless systems.

The main synthesizer consists of a 32/33-modulus prescaler with an 11-bit counter, a phase-frequency detector, and a charge pump. The phase-frequency detector is referenced to an internal reference frequency that is derived from an external TCXO signal. The phase-frequency detector is also provided with a dead-zone compensation circuit that reduces synthesizer phase noise during locked conditions.

Each auxiliary synthesizer consists of an independent 8/9-modulus prescaler with an 11-bit counter, a phase-frequency detector, and a charge pump. Similar to the main synthesizer, each auxiliary synthesizer's phase-frequency detector is referenced to an internal reference frequency that is derived from an external TCXO signal.

The external TCXO signal is prescaled by an 11-bit counter and then distributed to three independent postscalers. Each postscaler provides a selectable, divide-by-1, -2, -4, or -8 function before the reference signal is distributed to the associated synthesizer phase detector. The reference frequency prescaler and independent postscalers are software programmable.

To achieve minimum lock-up time, each synthesizer contains a speed-up mode charge pump capable of providing 2 mA output current and an analog switch that can change the loop-filter time constant. The duration of the speed-up mode operations can be independently controlled with software.

The states of the three internal lock detectors are provided on a programmable, combinational logic output; each synthesizer can be selected independently or ANDed t