HMC701LP6CE Datasheet, PDF (12/46 Pages) Hittite Microwave Corporation – 8 GHz 16-Bit Fractional-N Synthesizer

v03.0709
HMC701LP6CE
8 GHz 16-Bit Fractional-N Synthesizer
Lock Detect Windows (gpo_sel=2)
Setting register gpo_sel = 2 (Reg1Bh<3:0> Table 37) results in the lock detect window (Figure 21) and the phase
frequency detector UP and DN output control signals (Figure 24) 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.
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Figure 13. 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.
Internal Synchronized Frac strobe with clocks (gpo_sel= 4)
Setting register gpo_sel=4 in (Reg1Bh<3:0> Table 37) gives visibility into the internally synchronized strobe that
is generated when commanding a frequency change by writing to the frac register. The internal strobe initiates the
update to the fractional modulator, and the VCO SPI transfer if applicable. The internal frac strobe, the ref path divider
output and the sine reference input are buffered out to GPO1,GPO2 and GPO3 respectively as shown in Figure 14. In
this mode, GPO1 may be used to trigger an external instrument = when doing frequency hopping tests for example.
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