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

17

HMC702LP6CE

v10.0812

14 GHz 16-BIT FRACTIONAL-N PLL

PFD Lock Detect

the Lock Detect circuit in the HMc702LP6cE places a one shot window around the reference. the one shot window

may be generated by either an analog one shot circuit or a digital one shot based upon an internal ring oscillator timer.

is enabled.

the lock detect window to declare lock. if for example we set lkd_wincnt_max = 1000 , then the Vco arrival would

have to occur inside the selected lock widow 1000 times in a row to be declared locked. When locked the Lock Detect

the Lock Detect flag, ro_lock_detect.

Lock Detect flag is also output to the LD_SDO pin according to lkd_to_sdo_always (Reg1Ah<13>) and lkd_to_sdo_

on LD_DSO. clearing lkd_to_sdo_always and setting lkd_to_sdo_automux_en will display the Lock Detect flag on

LD_SDO except when a serial port read is requested, in which case the pin reverts temporarily to the Serial Data out

pin, and returns to the lock detect function after the read is completed.

Figure 12. Normal Lock Detect Window

Lock Detect with Phase Offset

When operating in fractional mode the linearity of the charge pump and phase detector are more critical than in

integer mode. the phase detector linearity is worse when operated with zero phase offset. Hence in fractional mode

it is necessary to offset the phase of the reference and the Vco at the phase detector. in such a case, for example

with an offset delay, as shown in Figure 13, the mean phase of the Vco will always occur after the reference. the

lock detect circuit window can be made more selective with a fixed offset delay by setting win_asym_enable and

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

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