EM3581 查看數據表（PDF） - Silicon Laboratories

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EM3581

High-Performance, Integrated ZigBee/802.15.4 System-on-Chip Family

Silicon Laboratories 

EM358x

2. Typical Connection Diagrams

Figure 2.1 illustrates the typical application circuit.

Note: The circuit shown in Figure 2.1 is for example purposes only. For a complete reference design, please download one of

the latest Ember Hardware Reference Designs from the Silicon Labs website (www.silabs.com/zigbee-support).

The Balun provides an impedance transformation from the antenna to the EM358x for both TX and RX modes.

L4, along with the PCB trace parasitics and the ceramic balun impedence, provide the optimal RF path for

maximum transmit power and receive sensitivity for the EM358x system.

The harmonic filter (L5, L6, C7, C8 and C9) provides additional suppression of the second harmonic, which

increases the margin over the FCC limit.

The 24 MHz crystal, Y2, with loading capacitors is required and provides the high-frequency crystal oscillator

source for the EM358x’s main system clock. The optional 32.768 kHz crystal, Y1, with loading capacitors

generates a highly accurate low-frequency crystal oscillator for use with peripherals, but it is not mandatory as the

low-frequency internal RC oscillator can be used.

Loading capacitance and ESR (C3 and R3) provides proper loading for the internal 1.8 V regulator.

Loading capacitance C4 provides proper loading for the internal 1.25 V regulator, no ESR is required because it is

contained within the chip.

Resistor R7 reduces the operating voltage of the flash memory. This reduces current consumption and improves

sensitivity by 1 dB when compared to not using it.

Various decoupling capacitors, C12 – C21, are required, these should be placed as close to their corresponding

pins as possible. For values and locations see one of the Silicon Labs reference designs.

An antenna impedance matched to 50  is required.

Rev 1.0

9

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