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Evaluates: MAX3521

MAX3521 Evaluation Kit

Detailed Description

Gain Calculations

The 1:4 impedance ratio transformer (T1) on the EV kit

converts the unbalanced 50Ω impedance of the signal

generator to a balanced 200Ω, matching the input of the

device. T1 is included to assist in evaluation of the device

using standard 50Ω lab equipment. It is not required for

most applications.

A 1:4 impedance ratio corresponds to a 1:2 voltage ratio,

or 6dB voltage gain. The power loss of T1, which must

be included, is approximately 0.3dB across the operating

frequency range of the device, giving a total voltage gain

due to T1 of 5.7dB.

A minimum loss pad (MLP) on the output of T2 trans-

forms the 75Ω output impedance of the device to 50Ω

test-equipment impedance, with a voltage loss of 7.4dB.

Because the 1:2 impedance ratio output transformer (T2)

is required in the application, we do not include the loss in

this transformer in the voltage-gain calculation.

To calculate the voltage gain of the device from 50Ω

power measurements at RFIN and RFOUT on the EV kit:

Layout Considerations

The EV kit can serve as a guide for PCB layout. Keep

RF signal lines as short as possible to minimize losses

and radiation. To minimize second-order distortion, traces

in the balanced input and output circuitry should be

as symmetric as possible. The exposed pad must be

soldered evenly to the board’s ground plane for proper

operation. Use abundant vias beneath the exposed pad

for maximum heat dissipation. Use abundant ground vias

between RF traces to minimize undesired coupling.

To minimize coupling between different sections of the

device, the ideal power-supply layout is a star configuration,

which has a large decoupling capacitor at the central

impedance to ground at the frequency of interest. Do

not share ground vias among multiple connections to the

PCB ground plane.