HMC701LP6CE Datasheet, PDF (15/46 Pages) Hittite Microwave Corporation – 8 GHz 16-Bit Fractional-N Synthesizer

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HMC701LP6CE
8 GHz 16-Bit Fractional-N Synthesizer
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Figure 15. Conventional Synthesizer with VCO
Step Tuned VCO Support
In addition to conventional varactor tuned VCOs, the HMC701LP6CE also supports step tuned type VCOs, as shown
Figure 16. A step tuned VCO allows the user to center the VCO on the required output frequency while keeping the
varactor tuning voltage optimized near the mid-voltage tuning point of the synthesizer charge pump. This helps to keep
the tuning sensitivity more linear and reduces variations in kvco, which in turn minimizes variations in the closed loop
bandwidth of the locked oscillator. VCOs with up to 6-bits of discrete digital tuning, and up to 10-bits of total control
bits, are supported via a simple 3-wire VCO Serial Port.
If a step tuned VCO is used, the VCO switches are normally controlled automatically by the synthesizer using the auto
tune feature. The VCO switches may also be controlled directly from register bits Reg0B<4:0> of spivco_direct_data,
(Reg0Bh Table 22) via direct serial port access for testing or for other special purpose operation. Other control bits
specific to the VCO may be output from Reg0B<9:5>.
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