M2031 MA-COM [M/A-COM Technology Solutions, Inc.], M2031 Datasheet - Page 2

• Manufacturer Part Number: M2031
• Manufacturer: MA-COM [M/A-COM Technology Solutions, Inc.]

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Printed Circuit Board Design
for LSM1 VCO’s
Application Note
M2031
To tolerate the impedance mismatch introduced by
components such as mixers and prescalers some
form of isolation is needed at the RF output. This
can be achieved by using a 10 dB pad and buffer
amplifier. Insufficient isolation of the VCO output
may result in output power variations, degraded
phase noise performance and increased output
frequency pulling.
The LSM1 VCO design incorporates a bypass ca-
pacitor on the Vcc input to suppress supply gener-
ated noise. Additional filtering is recommended to
reduce supply noise and its effect on VCO phase
noise performance. Care should also be taken to
minimize the introduction of noise from the tune
voltage input by additional filtering as necessary.
Electrical and/or thermal considerations may also
require the board to contain plated through holes
located under the pad of a surface mount package.
When this is necessary, the recommended plated
through hole diameter is 0.25 to 0.38 mm (0.010 to
0.015 inch). This diameter range, along with the
solder’s viscosity, helps to prevent solder flow
down these holes. Although a 0.8 mm (0.031 inch)
diameter hole is typically used, holes this size will
drain solder away from the base of the package
and will make solder paste thickness more difficult
to control.
Thermal resistance through the circuit board will be
a function of the pcb material and thickness, the
quantity and location via holes, the proximity of any
additional thermal loads and whether forced air
cooling is employed. Thorough testing of the proto-
type is the only way to prove the adequacy of a
thermal design. In general these VCO’s can be
considered as low power dissipation components
and no special precautions need to be taken.
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Rev. V4