For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824

Phone: 978-250-3343

Fax: 978-250-3373

Order On-line at www.hittite.com

Application Support: Phone: 978-250-3343 or apps@hittite.com

19

HMC701LP6CE

v09.1112

8 GHz 16-BIT FRACTIONAL-N PLL

Charge Pump Phase Offset

Either of the UP or Dn charge pumps may have a Dc leakage or “offset” added. the leakage forces the phase detector

to operate with a phase offset between the reference and the divided Vco inputs. it is recommended to operate with

a phase offset when using fractional mode to reduce non-linear effects from the UP and Dn pump mismatch. Phase

noise in fractional mode is strongly affected by charge pump offset.

Dc leakage or “offset” may be added to the UP or Dn pumps using cp_UPoffset_sel and cp_DNoffset_sel (Reg08

as an example, if the main pump gain was set at 1ma, an offset of 373ua would represent a phase offset of about

(392/1000)*360 = 133 degrees. For best spectral performance in Fractional Mode the leakage current should be

programmed to:

required Leakage current (µa) = (2.5E-9 + 4xtvco) x Fcomparison (Hz) x cP current (µa)

Leakage Current should never exceed 25% of the programmed CP current.

Figure 14. Charge Pump Gain, Trim and Phase Offset Control

Frequency Programming

the HMc701LP6cE can operate in either fractional mode or integer mode. in integer mode of operation the delta

sigma modulator is disabled. Frequency programming and mode control is described below.

Fractional Frequency

the fractional frequency synthesizer, when operating in fractional mode, can lock to frequencies which are fractional

multiples of the reference frequency.

Fractional Frequency

of VCO

(EQ 13)

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