Low-Power Direct Digital Modulation Frequency Synthesizer
Preliminary Datasheet V1.2
PS2500 2.2 GHz Fractional-N Frequency Synthesizer
- 1 -
Features
Product Description
Philsar Semiconductor Inc.
146 Colonnade Road S.
Nepean, Ontario, Canada
K2E 7Y1
Tel: 613-274-0922
Fax: 613-274-0915
www.philsar.com
PMP-001-DS2 V1.2
The PS2500 Direct Digital Modulation Fractional-N frequency synthesizer
provides ultra-fine frequency resolution, fast switching speed, and low
phase-noise performance. This synthesizer is a key building block in designing
high-performance narrowband and multi-band radio systems that require low
power and fine step size.
The ultra-fine step size of less than 100 Hz allows this synthesizer to be used in
very narrowband wireless applications. With proper temperature sensing or
through control channels, the synthesizer’s fine step size can compensate for
crystal oscillator or IF filter drift. As a result, crystal oscillators or crystals can
replace temperature-compensated or ovenized crystal oscillators, reducing parts
count and associated component cost. The PS2500’s fine step size can also be
used for doppler shift corrections.
The PS2500 has a phase noise floor of -92 dBc/Hz up to 2.2 GHz operation.
This is permitted by the on-chip low noise prescalers and low divide ratios
provided by the IC’s high fractionality.
Reference crystals or oscillators up to 50 MHz can be used with the PS2500.
The crystal frequency is divided down by independent programmable dividers
(1 to 32) for the main and auxiliary synthesizers. The phase detectors can
operate at a maximum speed of 25 MHz, permitting better phase noise due to
the lower division value. With a high reference frequency, the loop bandwidths
can also be increased. Larger loop bandwidths improve the settling times and
reduce in-band phase noise. Typical switching times of less than 100
µs can
thus be achieved with a 10 MHz reference. The PS2500’s lower in-band phase
noise also permits the use of lower cost Voltage Controlled Oscillators (VCOs)
in customer applications.
The PS2500 has a Frequency Power SteeringTM circuit (patent pending), which
assists the loop filter to steer the VCO when the frequency is too fast or too
slow. In this configuration, acquisition times of up to five times faster than
conventional phase/frequency detectors can be achieved.
The unit operates with a 3-wire, high-speed serial interface. A combination of a
large bandwidth, fine resolution, and the 3-wire, high-speed serial interface
allows for a direct phase and frequency modulation of the VCO. This supports
any constant envelope and continuous phase modulation which means any
analog FM or digital FM. This capability can eliminate the need for I & Q
DACs, quadrature upconverters, and IF filters from the transmitter portion of
the radio system.
• 2.2 GHz maximum operating
frequency
• 500 MHz maximum auxiliary
synthesizer
• Ultra-small step size 100 Hz or
less
• High-reference frequency enables
larger loop bandwidth PLL
• Fast switching speed
• Phase-noise to -92 dBc/Hz inside
the loop filter bandwidth
• Spurious -70 dBc/Hz inside the
loop filter bandwidth
• Software programmable
power-down modes
• High-speed serial interface
• 3-wire programming
• Programmable division ratios on
reference frequency
• Phase detectors with
programmable gain provide a
programmable loop bandwidth
• Frequency Power SteeringTM
speeds up acquisition 5x with
same loop bandwidth
• On-chip crystal oscillator
• Frequency adjust for temperature
compensation
• Direct digital modulation
• 3 volt operation
• 5 volt output to loop filter
• 28-pin EP-TSSOP package
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