Freescale Freedom Development Board FRDM-CR20A User’s Guide, Rev. 0, 04/2015
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Freescale Semiconductor, Inc.
FRDM-CR20A development board
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Frequency range is 2360 to 2480 MHz
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The MCR20 transceiver features an integrated transmit/receive switch to its differential
bidirectional RF input/output pin
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Board features a low component count RF matching network with off-chip 1:1 Balun
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“F” printed metal antenna for a small footprint, low-cost design
The layout has provision for out-of-band signal suppression (components L1 and C5) if required.
Figure 6
shows the typical topology for the RF circuitry. A footprint is available to install RF connector J5 for
measurement purposes. When using J5, C1 should be installed and C4 removed.
Figure 6. FRDM-CR20A RF circuitry
4.2.2
Clocks
The FRDM-CR20A provides two clocks:
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32 MHz Reference Oscillator -
Figure 7
shows the external 32 MHz external crystal Y1. This
mounted crystal must meet the specifications outlined in the AN3251 application note. The IEEE
802.15.4 Standard requires that the frequency be accurate to less that +/-40 ppm.
— At 25°C, it is desired to have the frequency accurate to +/-10 ppm or less to allow for
temperature variation.
— Capacitors C16 and C17 provide the bulk of the crystal load capacitance.
— To measure the 32 MHz oscillator frequency, signal CLKOUT (pin-16) can optionally be
configured to provide a buffered output clock signal.
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