HMC701LP6CE Datasheet, PDF (10/46 Pages) Hittite Microwave Corporation – 8 GHz 16-Bit Fractional-N Synthesizer

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HMC701LP6CE
8 GHz 16-Bit Fractional-N Synthesizer
VCO Path
The RF path from the VCO to the phase detector, is referred to as the VCO path. The VCO path consists of an input
isolation buffer and a multi-modulus prescaler, or simply the N divider. The N divider is controlled by the fractional
modulator. This path operates with inputs directly from the external VCO.
RF Input Stage
The synthesizer RF input stage routes the external VCO to the phase detector via a 16-bit fractional divider. The RF
input path is rated to operate nominally from 100 kHz to 8 GHz in fractional and 9 GHz in integer modes. The RF input
stage also provides isolation between the VCO and the prescaler. The RF input stage is a differential common emitter
stage, DC coupled for maximum flexibility. The input is protected by ESD diodes as shown in Figure 11. Normally the
RF input is AC coupled to a single ended external source. The RFINP buffer is well matched from a single ended
50 Ohm source above about 3.5 GHz, with the complimentary input grounded. If a better match is required at low
frequency a simple shunt 50 Ohm resistor can be used external to the package. If a differential external source is used
then the two input pins may be used for best performance.
11
Figure 11. RF Input Stage
RF Path ’N’ Divider
The main RF path divider is capable of average divide ratios between 65,531 and 36 in fractional mode, and 65,535
to 32 in integer mode. The reason for the difference between integer and fractional modes is that the fractional divider
actually divides by up to ±4 from the average divide number. Actual division ratios when used with a given VCO will
depend upon the reference frequency used and the desired output band.
For price, delivery, and to place orders, please contact Hittite Microwave Corporation:
20 Alpha Road, Chelmsford, MA 01824 Phone: [phone] Fax: [phone]
Order On-line at www.hittite.com
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