HMC701LP6CE Datasheet, PDF (14/46 Pages) Hittite Microwave Corporation – 8 GHz 16-Bit Fractional-N Synthesizer

v03.0709
HMC701LP6CE
8 GHz 16-Bit Fractional-N Synthesizer
Δ∑ Modulator Outputs (gpo_sel=10)
Setting register gpo_sel=10 (Reg1B<3:0> Table 37) assigns the three lsb’s of the delta sigma modulator output to
GPO<3:1> , where GPO1 is the lsb. This feature allows the possibility of using the HMC701LP6CE as a general
purpose digital delta sigma modulator for many possible applications.
External VCO
The HMC701LP6CE is targeted for ultra low phase noise applications with an external VCO. The synthesizer has
been designed to work with VCOs that can be tuned nominally over 0.5 to 4.5 Volts on the varactor tuning port with a
+5V charge pump supply voltage. Slightly wider ranges are possible with a +5.5V charge pump supply or with slightly
degraded performance. An external opamp active filter is required to support VCOs with tuning voltages above 5V.
External VCO with Active Inverting OpAmp Loop Filter
An external opamp active filter is required to support external VCOs with tuning voltages above 5V. If an inverting
opamp is used with a positive slope VCO, phase_sel Reg05h <0> = 1 Table 16 must be set to invert the PFD phase
polarity and obtain correct closed loop operation.
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