HMC701LP6CE Datasheet, PDF (12/40 Pages) Hittite Microwave Corporation – 8 GHz 16-Bit Fractional-N Synthesizer

v09.1112
HMC701LP6CE
8 GHz 16-BIT FRACTIONAL-N PLL
synthesizer requires very low phase noise from the crystal, hence it is desirable to isolate other circuits from the
crystal itself and allow the synthesizer sole use of the low phase noise crystal.
gpo_sel=1 also routes the 250 MHz 14-bit reference path divider to GP02 and the 16-bit 7 GHz VCO path prescaler
output to GP01. This option allows the synthesizer to function as a stand alone fractional or integer prescaler and
provides visibility into the prescaler and reference path timing for sensitive applications.
Figure 6. gpo_01 Outputs
Lock Detect Windows (gpo_sel=2)
Setting register gpo_sel = 2 (Reg1Bh<3:0> Table 37) results in the lock detect window (Figure 11) and the phase
frequency detector UP and DN output control signals (Figure 14) to be routed to pins GPO1, GPO3 and GPO2
respectively. This option gives insight into the Lock Detection Process and could allow the synthesizer to be used with
an external charge pump.
Figure 7. gpo_02 Outputs
Anti-cycle Slip Waveforms (gpo_sel = 3)
Setting register gpo_sel=3 (Reg1Bh<3:0> Table 37) gives visibility into the anti-cycle slipping function of the PFD
as described in section Cycle Slip Prevention (CSP). Three waveforms, reference path freq > VCO path freq, vco
path freq > ref path freq, and a PFD strobe which holds the PFD at maximum gain, are routed to GPO3, GPO2, and
GPO1 respectively. These lines will be active during frequency pull-in and will indicate instantaneously which signal,
reference or vco path is greater in frequency. The PFD strobe gives insight into when the PFD is near maximum gain
at 2π. The PFD strobe will be active until the VCO pulls into lock.
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