Wireless ICs
Volume 9, Issue 5 YOUR SEMICONDUCTOR SOLUTIONS RESOURCE

Ultrabroadband PLL with Integrated Low Noise VCO Covers All Cellular Bands

A long time challenge for RF designers has been the need to develop an LO synthesizer that is both high performance and highly adaptable and reconfigurable. Traditionally, RF designers have sought to optimize the loop filter in order to find a suitable trade-off between phase noise, spurious signals, and lock time. This approach often resulted in synthesizer designs that were highly band specific and, therefore, not easily reconfigurable. This approach resulted in longer design cycle times, longer time to market, and more unwieldy BOM structures—hence, more difficult production logistics and supply chain challenges.

Solution
The ADF4350 is a PLL with fully integrated on-chip low noise VCO that addresses this particular challenge head on. The complete synthesizer can cover a continuous frequency range from 137.5 MHz to 4400 MHz, addressing all major cellular bands. The PLL can operate in either fractional-N mode or integer-N mode. The on-chip VCO displays phase noise of –137 dBc/Hz at a 1 MHz offset when operating at 2.1 GHz, and –155 dBc/Hz at a 1 MHz offset when operating at 137.5 MHz. This capability corresponds to an integrated rms phase error of 0.36° at 2.1 GHz and 0.02° at 137.5 MHz. The ADF4350 has an integrated voltage controlled oscillator (VCO) with an octave output frequency ranging from 2200 MHz to 4400 MHz. On-chip divide-by-1/-2/-4/-8/-16 circuits allow the user to generate RF output frequencies as low as 137.5 MHz.

With exceptional RF performance, feature rich functionality, and unsurpassed flexibility all in a single fully integrated 5 mm × 5 mm LFCSP package, the ADF4350 is indeed a highly attractive solution for LO generation that covers all major cellular bands.

For those customers who require enhanced phase noise performance through the use of an external VCO, the ADF4150 is available.

adf4350

ADF4350 Features

  • Output frequency range: 137.5 MHz to 4400 MHz
  • Fractional-N synthesizer and integer-N synthesizer
  • Low phase noise VCO
  • Programmable divide-by-1/-2/-4/-8/-16 output
  • Programmable output power level
  • RF output mute function

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