MAX2023_1中文资料(4)

MAX2023 Evaluation KitEvaluates: MAX2023

Figure 1. Example Diplexer Network for GSM 1800/1900 Applications

As shown in Figure 1, providing an RC termination oneach of the I+, I-, Q+, Q- ports reduces the amount ofLO leakage present at the RF port under varying temp-erature, LO frequency, and baseband drive conditions.Note that the resistor value is chosen to be 50 with acorner frequency 1 / (2πRC) selected to adequately filterthe fLOand 2fLOleakage, yet not affecting the flatnessof the baseband response at the highest baseband frequency. The common-mode fLOand 2fLOsignals atI+/I- and Q+/Q- effectively see the RC networks andthus become terminated in 25 (R/2). The RC networkprovides a path for absorbing the 2fLOand fLOleakage,while the inductor provides high impedance at fLOand2fLOto help the diplexing process.

The MAX2023 EV kit includes flexibility for a diplexernetwork to be installed if desired. See Figure 3 fordetails on the EV kit schematic.

The MAX2023 evaluation board can be a guide for yourboard layout. Pay close attention to thermal design andclose placement of components to the IC. TheMAX2023 package’s exposed paddle (EP) conductsheat from the device and provides a low-impedanceelectrical connection to the ground plane. The EP mustbe attached to the PCB ground plane with a low ther-mal and electrical impedance contact. Ideally, this isachieved by soldering the backside of the packagedirectly to a top metal ground plane on the PCB.Alternatively, the EP can be connected to an internal orbottom-side ground plane using an array of plated viasdirectly below the EP. The MAX2023 EV kit uses nineevenly spaced 0.016in-diameter, plated through holesto connect the EP to the lower ground planes.

Depending on the ground plane spacing, large sur-face-mount pads in the IF path may need to have theground plane relieved under them to reduce parasiticshunt capacitance.

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MAX2023 Evaluation Kit

Evaluates: MAX2023

Figure 2. Test Setup Diagram

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