TRC104 2.4 GHz Transceiver Reference Design

RF Monolithics, AN0901

Introduction

This application note presents a PCB reference design for RFM’s TRC104 2.4 GHz transceiver IC. The reference design, including a PCB antenna, easily fits on one square inch of circuit board. Two RF inductors are implemented as circuit board traces, avoiding the cost of discrete inductors. The reference design schematic is shown in Figure 1 below.

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Figure 1.	TRC104 Reference Design Schematic

Bill of Materials

The TRC104 Reference Design BOM is presented below:

Circuit Board Layers

Figure 2 shows the TRC104 reference design top assembly. Power supply and digital I/O signals are organized on the left, the printed antenna is on the right. A wide variety of microcontrollers can be used to control the TRC104. Note RF inductors L1 and L2 are implemented as circuit board traces. PADs PCB design files and Gerber files of the reference design layout are available here.

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Figure 2.	Top Assembly	Figure 3.	Top Silkscreen

The top silkscreen is shown in Figure 3 above.

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Figure 4.	Top Solder Mask	Figure 5.	Top Etch

The top solder mask is shown in Figure 4.

The top etch pattern is shown in Figure 5. Using ±5% NPO RF capacitors where specified in the bill of materials is important to reference design performance.

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Figure 6.	Drill & Layer Data

The drill and layer data is provided in Figure 6. The reference design is implemented on a two-sided 0.031 inch board with 1 oz copper traces.

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Figure 7.	Bottom Etch	Figure 8.	Bottom Solder Mask

Figure 7 shows the reference design bottom etch pattern.

Figure 8 shows the TRC104 reference design bottom solder mask.

Figure 9.	Assembled Reference Design PCB

Figure 9 shows the assembled TRC104 reference design PCB.

Minimizing Sleep Mode Current

Several TRC104 digital I/O lines must held logic low to achieve minimum sleep mode current, as discussed in Section 4.1 of the TRC104 data sheet:

• SDAT
• SCLK
• INT
• RSSID

These lines can be held low by the host microcontroller during sleep mode, or the host microcontroller pins can be tri-stated and 100K pull-down resistors can be used. Note that the 100K pull-down resistors are not included on the TRC104 reference design.

Reference Design Testing

The TRC104 reference design has been tested in a variety of office environments and typically achieves an operating range of 50 feet (15 meters) when transmitting data at 1 Mb/s.

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