SKY72310-362LF Datasheet, PDF (1/19 Pages) Skyworks Solutions Inc. – General purpose RF systems

DATA SHEET
SKY72310: Spur-Free, 2.1 GHz Single Fractional-N Frequency
Synthesizer
Applications
• General purpose RF systems
• 2.5G and 3G wireless infrastructure
• Broadband wireless access
• Low bit rate wireless telemetry
• Instrumentation
• L-band receivers
• Satellite communications
Features
• Spur-free operation
• 2.1 GHz maximum operating frequency
• Ultra-fine step size, 100 Hz or less
• High internal reference frequency enables large loop bandwidth
implementations
• Very fast switching speed (e.g., below 100 µs)
• Phase noise to –91 dBc/Hz inside the loop filter bandwidth
@ 1800 MHz
• Software programmable power-down modes
• High-speed serial interface up to 100 Mbps
• Three-wire programming
• Programmable division ratios on reference frequency
• Phase detector with programmable gain to provide a
programmable loop bandwidth
• Frequency power steering further enhances rapid acquisition
time
• On-chip crystal oscillator
• Frequency adjust for temperature compensation
• 3 V operation
• 5 V output to loop filter
• QFN (24-pin, 4 x 4 mm) Pb-free (MSL3, 260 °C per JEDEC J-
STD-020) package
Skyworks offers lead (Pb)-free, RoHS (Restriction of
Hazardous Substances) compliant packaging.
Description
Skyworks SKY72310 fractional-N frequency synthesizer provides
ultra-fine frequency resolution, fast switching speed, and low
phase-noise performance. This synthesizer is a key building block
for high-performance radio system designs 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 Intermediate Frequency (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 device’s fine step size can also be used for
Doppler shift corrections.
The SKY72310 has a phase noise floor of –90 dBc/Hz up to
2.1 GHz operation as measured inside the loop bandwidth. This is
permitted by the on-chip low noise dividers and low divide ratios
provided by the device’s high fractionality.
Reference crystals or oscillators up to 50 MHz can be used with
the SKY72310. The crystal frequency is divided down by
independent programmable dividers (1 to 32) for the synthesizer.
The phase detector can operate at a maximum speed of 25 MHz,
which allows 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. Therefore, typical switching times of
less than 100 µs can be achieved. The lower in-band phase noise
also permits the use of lower cost Voltage Controlled Oscillators
(VCOs) in customer applications.
The SKY72310 has a frequency power steering circuit that helps
the loop filter to steer the VCO when the frequency is too fast or
too slow, further enhancing acquisition time.
The unit operates with a three-wire, high-speed serial interface. A
combination of large bandwidth, fine resolution, and the three
wire interface allows for direct frequency modulation of the VCO.
This supports any continuous phase, constant envelope
modulation scheme such as Frequency Modulation (FM),
Frequency Shift Keying (FSK), Minimum Shift Keying (MSK), or
Gaussian Minimum Shift Keying (GMSK).
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
200705E • Skyworks Proprietary and Confidential information • Products and Product Information are Subject to Change Without Notice • July 30, 2008
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