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

Phone: 978-250-3343

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Order On-line at www.hittite.com

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19

HMC702LP6CE

v10.0812

14 GHz 16-BIT FRACTIONAL-N PLL

Charge Pump Gain

a simplified diagram of the charge pump is shown in Figure 15. charge pump up and down gains are set by cp_

value. Each of the UP and Dn charge pumps consist of 5-bit charge pumps with lsb of 125 µa. the current gain of the

pump, in amps/radian, is equal to the gain setting of this register divided by 2π.

For example if both cp_UPcurrent_sel and cp_DNcurrent_sel are set to ’01000’ the output current of each pump will

be 1ma and the gain Kp = 1ma/2π radians, or 159 ua/rad.

Charge Pump Gain Trim

in most applications Gain trim is not used. However it is available for special applications.

Each of the UP and Dn pumps may be trimmed separately to more precise values to improve current source matching

of the UP and Dn values, or to allow finer control of pump gain.

the pump trim controls are 3-bits, binary weighted for UP and Dn, in cp_UPtrim_sel and cp_DNtrim_sel respectively

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 + 8xtvco) x Fcomparison (Hz) x cP current (µa)

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

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.

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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