(Preliminary)

Analog Frequency Multiplier

PL565-68 VCXO

INDUCTOR VALUE OPTIMIZAT ION

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 from

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 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

PCB side

- Cinternal at L2X = 7.625 pF

- LWB1 = 2 nH, (2 places), Stray inductance

- Cpad = 1.0 pF, Bond pad and its ESD circuitry

- Cstray = 0.5 pF, Stray capacitance

- C11 = 0.4 pF, The following amplifier stage

- L2X = 2x inductor

- C2X = 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 required 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.