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CC1050-RTR1 数据表(PDF) 29 Page - Texas Instruments |
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CC1050-RTR1 数据表(HTML) 29 Page - Texas Instruments |
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29 / 40 page ![]() CC1050 SWRS044 Page 29 of 40 PCB Layout Recommendations A two layer PCB is highly recommended. The bottom layer of the PCB should be the “ground-layer”. Chipcon provide reference designs that should be followed in order to achieve the best performance. The top layer should be used for signal routing, and the open areas should be filled with metallisation connected to ground using several vias. The ground pins should be connected to ground as close as possible to the package pin using individual vias. The de- coupling capacitors should also be placed as close as possible to the supply pins and connected to the ground plane by separate vias. The external components should be as small as possible and surface mount devices should be used. Precaution should be used when placing the microcontroller in order to avoid interference with the RF circuitry. In certain applications where the ground plane for the digital circuitry is expected to be noisy, the ground plane may be split in an analogue and a digital part. All AGND pins and AVDD de-coupling capacitors should be connected to the analogue ground plane. All DGND pins and DVDD de-coupling capacitors should be connected to the digital ground. The connection between the two ground planes should be implemented as a star connection with the power supply ground. A development kit with a fully assembled PCB is available, and can be used as a guideline for layout. Antenna Considerations CC1050 can be used together with various types of antennas. The most common antennas for short range communication are monopole, helical and loop antennas. Monopole antennas are resonant antennas with a length corresponding to one quarter of the electrical wavelength ( λ/4). They are very easy to design and can be implemented simply as a “piece of wire” or even integrated into the PCB. Non-resonant monopole antennas shorter than λ/4 can also be used, but at the expense of range. In size and cost critical applications such an antenna may very well be integrated into the PCB. Helical antennas can be thought of as a combination of a monopole and a loop antenna. They are a good compromise in size critical applications. But helical antennas tend to be more difficult to optimise than the simple monopole. Loop antennas are easy to integrate into the PCB, but are less effective due to difficult impedance matching because of their very low radiation resistance. For low power applications the λ/4- monopole antenna is recommended giving the best range and because of its simplicity. The length of the λ/4-monopole antenna is given by: L = 7125 / f where f is in MHz, giving the length in cm. An antenna for 869 MHz should be 8.2 cm, and 16.4 cm for 434 MHz. The antenna should be connected as close as possible to the IC. If the antenna is located away from the input pin the antenna should be matched to the feeding transmission line (50 Ω). For a more thorough primer on antennas, please refer to Application Note AN003 SRD Antennas available from Chipcon’s web site. Not Recommended for New Designs |
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