Data Sheet

ADRF5238

APPLICATIONS INFORMATION

analog.com

Rev. 0 | 12 of 13

The ADRF5238 has one power supply pin (VDD) and two digital

control pins (CTRL and EN). Figure 17 shows the external compo-

nents and connections for the supply pin. The VDD pin is decou-

pled with a 100pF multilayer ceramic capacitor. The ADRF5238

pinout allows the placement of the decoupling capacitors close to

the device. No other external components are needed for bias and

operation, except DC blocking capacitors on the RF pins (RFC,

RF1, and RF2). Wideband capable DC blocking capacitors are

recommended for best performance.

Figure 17. Recommended Schematic

RECOMMENDATIONS FOR PRINTED CIRCUIT

BOARD DESIGN

The RF ports are matched to 50Ω internally and the pinout is

designed to mate a coplanar waveguide (CPWG) with a 50Ω char-

acteristic impedance on the PCB. Figure 18 shows the referenced

CPWG RF trace design for an RF substrate with 10mil thick Rogers

RO4350B dielectric material. The RF trace with an 18mil width

and 13mil clearance is recommended for 2.8mil finished copper

thickness.

Figure 18. ADRF5238-EVALZ Stack-Up

Figure 19 shows the routing of the RF traces, supply, and control

signals from the ADRF5238. The ground planes are connected with

densely filled through vias for optimal RF and thermal performance.

The primary thermal path for the ADRF5238 is the bottom side.

Figure 19. PCB Routings

Figure 20 shows the recommended layout from the RF pins (RFC,

RF1, and RF2) of the ADRF5238 to the 50Ω CPWG on the

referenced stack-up. PCB pads are drawn 1:1 to device pads.

The ground pads are drawn soldermask defined, and the signal

pads are drawn as pad defined. The RF trace from the PCB pad

is extended with the same width for a 10mil and tapered to the

RF trace. The paste mask is designed to match the pads of the

ADRF5238 without any aperture reduction. The paste mask is

divided into multiple openings for the paddle.

Figure 20. Recommended RF Pin Transition

For alternate PCB stack-ups with different dielectric thickness and

CPWG design, contact Analog Devices, Inc., Technical Support

Center for further recommendations.