PL560-08_12 Datasheet, PDF (7/12 Pages) Micrel Semiconductor – Analog Frequency Multiplier

(Preliminary) Analog Frequency Multiplier
PL560/565-08 VCXO Family
INDUCTOR VALUE OPTIMIZATION
The required inductor values for the best performance depend on the operating frequency, and the board layout
or module specifications. The listed values in this datasheet are based on the calculated parasitic values fr om
Micrel’s evaluation board design. These inductor values provide the user with a starting point to determine the
optimum inductor values. Additional fine-tuning may be required to determine the optimal solution.
The inductor is recommended to be a high Q small size 0402 or 0603 SMD component, and must be placed
between L2X / L4X and adjacent VDDOSC pin. Place inductor as close to the IC as possible to minimize parasitic
effects and to maintain inductor Q.
To assist with the inductor value optimization, Micrel has developed AFM “Tuning Assistant” documents. You can
download these documents from Micrel’s web site (www.micrel.com). The documents consist of tables with
recommended inductor values for certain output frequency ranges.
Figure 10: Diagram Representation of the Related System Inductance and Capacitance
DIE SIDE
- Cinternal at L2X = 7.625 pF , at L4X = 6.25 pF
- Cpad = 1.0 pF, Bond pad and its ESD circuitry
- C11 = 0.4 pF, The following amplifier stage
PCB side
- LWB1 = 2 nH, (2 places), Stray inductance
- Cstray = 0.5 pF, Stray capacitance
- L2X (L4X) = 2x or 4x inductor
- C2X (C4X) = range (0.1 to 2.7 pF), Fine tune
the tank, if used.
Work out the resonance of this network and you have a good first guess for the require d inductor values for
optimum performance. Non-linear behavior at large signal amplitudes can shift the tank resonance significantly,
especially at the L2X side, to a lower frequency than the calculation suggests. The Tuning Assistant documents
are based upon actual lab tests and are corrected for the non -linear behavior.
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