For price, delivery and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, Chelmsford, MA 01824

978-250-3343 tel • 978-250-3373 fax • Order On-line at www.hittite.com

Application Support: apps@hittite.com

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HMC700LP4 / 700LP4E

v11.0411

8 GHz 16-Bit Fractional-N PLL

Theory of Operation

the HMc700LP4(E) is targeted for ultra low phase noise applications. the synthesizer has been designed with very

low noise reference path, phase detector and charge pump.

External VCO

the HMc700LP4(E) is targeted for ultra low phase noise applications with an external Vco. the synthesizer charge

pump can operate with the charge pump supply as high as 5.5 Volts. the charge pump output at the varactor tuning

port, normally can maintain low noise performance to within 500mV of either ground or the upper supply voltage (see

Figure 7. HMC700LP4(E) Synthesizer with External VCO

High Performance Low Spurious Operation

the HMc700LP4(E) has been designed for the best phase noise possible in an integrated synthesizer. Spurious

signals in a synthesizer can occur in any mode of operation and can come from a number of sources. in general

spurious can be the result of interference that gets through the loop filter and modulates the input tuning port of the

Vco directly. it can also result from interference that modulates the Vco indirectly through power supplies, ground,

or output ports, or bypasses the loop filter due to poor isolation of the filter. it can also simply add to the output of the

synthesizer.

interference is always present at multiples of the PFD frequency, and the input reference frequency. Depending upon

the mode of operation of the synthesizer spurious may also occur at integer sub-multiples of the reference frequency.

if the fractional mode of operation is used the difference between the Vco frequency and the nearest harmonic of the

reference, will also create what are referred to as integer boundary spurs.

the synthesizer necessarily contains digital circuitry to control the prescaler. the circuitry mostly operates at the PFD

frequency. there is more circuitry active in fractional mode, hence more full switching cMoS is used and the potential

for interference is greater.

the HMc700LP4(E) has been designed and tested for low spurious performance in either integer or fractional mode

of operation. reference spurious levels are typically below -100 dBc, and in-band fractional boundary spurious are

typically below integrated phase noise, frequency planning can improve spurious performance in many cases.

reference spurious levels of below -100 dBc require superb board isolation of power supplies, isolation of the Vco from

the digital switching of the synthesizer, isolation of the Vco load from the synthesizer and isolation of the crystal from

the Vco. typical board layout, evaluation boards and application information are available for low spurious operation.

operation with lower levels of isolation in the application circuit board from those recommended by Hittite may result in

higher spurious levels.

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

rights of third parties that may result from its use. Specifications subject to change without notice. No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarks and registered trademarks are the property of their respective owners.

For price, delivery, and to place orders: Analog Devices, Inc.,

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106

Phone: 781-329-4700 • Order online at www.analog.com

Application Support: Phone: 1-800-ANALOG-D