Synthesizer integrates a phase-locked loop with fully integrated VCO, low dropout regulators, and tracking filter technology

By Warren
Miller, contributing writer

Applications in the aerospace and defense, test and
measurement, communications infrastructure, and high-speed converter markets
seem to be forever challenged with several common issues. These complex
applications require ever-increasing bandwidth, smaller board space footprints,
increased reliability, low noise, and increased clocking range and flexibility.

These capabilities are often competing against each other.
For example, higher integration can result in increased noise if internal
clocking and regulator circuits aren’t carefully isolated. Increased
flexibility results in less precise control of clocking with unacceptable
jitter and reference spurious. Operation over a wide temperature range can also
impact clocking precision. A next-generation synthesizer from Analog Devices
challenges the conventional wisdom that you can’t have it all.

The ADF4371 from Analog Devices, Inc. (ADI)
is a state-of-the-art highly-integrated synthesizer operating over an RF output
frequency range from 62.5 MHz to 32,000 MHz. On-chip resources include a
fractional-N and integer-N synthesizer phase-locked-loop (PLL), a fully
integrated voltage controlled oscillator (VCO) with four differential clock
outputs, and an integrated low dropout regulator (LDO). The entire device architecture
is highly configurable, using a common three-wire interface to program over 50
control registers. This high degree of programmability makes the ADF4371
appropriate for a very wide range of applications and can be used as the go-to
device in wireless infrastructure (MC-GSM, 5G), satellites/VSATs, test
equipment and instrumentation, and advanced clock generation applications.

The major blocks of the ADF4371 are shown in the following
figure which shows the VCO at the bottom left of the diagram and the low noise
LDO at the middle left of the diagram. The remainder of the diagram shows the
advanced PLL. The heart of the PLL is the programmable third-order fractional
interpolator (seen in the middle left of the diagram). It features a
high-resolution 39-bit fractional modulus that helps support the wide frequency

 ADF4371 Ultra-Wide Range Synthesizer Block Diagram. Image source:
Analog Devices.


The high degree of programmability offered by the ADF4371
doesn’t require performance sacrifices, as the advanced clock control metrics listed
below will satisfy even the most stringent requirements. 

  • Typical PFD spurious -100 dBc
  • Integrated RMS jitter
  • Normalized phase noise floor (FOM) -234 dBc/Hz
  • Phase frequency detector (PFD) operation to 250
  • Reference frequency operation to 600 MHz
  • Maintains frequency lock over −40°C to +105°C
  • Low phase noise, voltage controlled oscillator
  • Programmable divide by 1, 2, 4, 8, 16, 32, or 64

If your synthesizer application requires a high-level of
integration, high-bandwidth, reliability, a wide temperature operating range,
precision operation and flexibility, the ADF4371 may just be able to let you
have it all. 

Samples of the ADF4371 (7 mm x 7 mm, 48-lead LGA) are
available now, followed by production availability in September. ADI also offers the ADF4372 (7 mm
x 7 mm, 48-lead LGA) with
operation up to 16 GHz, which is sampling now; volume production will follow in
October. Both devices are supported by ADI’s ADIsimPLL circuit
design and evaluation tool