- Triple integer-N PLL for 1GHz applications
- Operation to 1.2 GHz for main synthesizer
- Operation to 250 MHz for auxilary synthesizers
- Fast lock-up time
- Dual modulus (32/33) RF and (8/9) IF prescalers
- Operates from 2.75-4.5 V supply
- Low power consumption (<10 mA @ 3V)
- Low stand-by power consumption (<10uA @ 3V)
- 24-pin TSSOP package
Summary: The Texas Instruments TRF2020 consists of main 1.2-GHz synthesizer and two auxiliary 250-MHz synthesizers in a 24-pin plastic thin shrink small-outline package (TSSOP). This combination allows a high degree of flexibility in the design of 900-MHz radio telephone systems by combining the digital elements of the synthesizers in a single package. Each synthesizer has an independent, dual-modulus prescaler and separate powerdown modes to allow the designer maximum flexibility.
The 1.2-GHz main synthesizer consists of a 32/33-modulus prescaler with an 11-bit counter, a conventional, phase-frequency, digital phase detector and charge pump. The phase detector is referenced to an internal reference frequency. The internal reference frequency is derived from an external TCXO signal. The phase detector design also incorporates dead-zone compensation, which reduces synthesizer phase noise during a locked condition.
The external TCXO signal is prescaled by an 11-bit counter then distributed to three independent postscalers. The postscalers provide a selectable, divide-by-1, -2, -3, -4 or –8 function before distributing the reference signal to each synthesizer phase detector. The reference frequency prescaler and independent postscalers are software programmable.
The 250-MHz auxiliary synthesizers consist of independent 8/9-modulus prescalers with 11-bit counter, conventional, phase-frequency, digital phase detectors and charge pumps.
To achieve minimum lock-up time, each synthesizer contains speed-up mode charge pumps capable of 2 mA and and analog switch which can be used to 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 together.
The device is programmed over a 3-wire, synchronous, serial data bus (clock, data, strobe) with bit rates as high as 20 Mbits/sec achievable. The data is partitioned into words in such a manner that static parameters may be sent once during initialization, and dynamic parameters, such as frequency, may be sent as often as needed. The TRF2020 is offered in a 24-pin plastic SSOP for production and is characterized for free-air operation from –40°C to 85°C free-air temperature.
