Evaluate: MAX2605–MAX2609
MAX2605–MAX2609 Evaluation Kits
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approximates the typical operating current specified
in the MAX2605–MAX2609 data sheet.
3) Connect the VCO output (OUT+ or OUT-) to a spec-
trum analyzer with a 50Ω coaxial cable.
4) Apply a positive variable DC voltage between 0.4V
and 2.4V to TUNE.
5) Check the tuning bandwidth on the spectrum analyz-
er by varying the tuning voltage (+0.4V to +2.4V).
Layout Considerations
The EV kit PC board can serve as a guide for laying out
a board using the MAX2605–MAX2609. Generally, the
VCC pin on the PC board should have a decoupling
capacitor placed close to the IC. This minimizes noise
coupling from the supply. Also, place the VCO as far
away as possible from the noisy section of a larger sys-
tem, such as a switching regulator or digital circuits.
The VCO’s performance is strongly dependent on the
availability of the external tuning inductor. For best per-
formance, use high-Q components and choose their val-
ues carefully. To minimize the effects of parasitic ele-
ments, which degrade circuit performance, place the
tuning inductor and C
BYP
close to the VCO. For higher-
frequency versions, include the parasitic PC board
inductance and capacitance when calculating the
oscillation frequency. In addition, remove the ground
plane around and under the tuning inductor to minimize
the effect of parasitic capacitance.
Noise on TUNE translates into FM noise on the outputs;
therefore, keep the trace between TUNE and the control
circuitry as short as possible. If necessary, use an RC
filter to further suppress noise, as done on the EV kits.
MAX2609 Component List
