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8168C-MCU Wireless-02/10
AT86RF212
7.8 Frequency Synthesizer (PLL)
The main PLL features are:
Generate RX/TX frequencies for all supported channels
Autonomous calibration loops for stable operation within the operating range
Two PLL interrupts for status indication
Fast PLL settling to support frequency hopping
7.8.1 Overview
The PLL generates the RF frequencies for the AT86RF212. During receive and transmit
operations, the frequency synthesizer operates as a local oscillator. The frequency
synthesizer is implemented as a fractional-N PLL with analog compensation of the
fractional phase error. The VCO is running at double of the RF frequency. Two
calibration loops ensure correct PLL functionality within the specified operating limits.
7.8.2 RF Channel Selection
The PLL is designed to support
one channel in the European SRD band from 863 to 870 MHz at 868.3 MHz
according to IEEE 802.15.4-2003/2006 (channel k = 0)
10 channels in the North American ISM band from 902 to 928 MHz with a channel
spacing of 2 MHz according to IEEE 802.15.4-2003/2006. The center frequency of
these channels is defined as
F = 906 + 2
(k-1) [MHz]
c
where k is the channel number ranging from 1 to 10.
4 channels in the Chinese WPAN band from 779 to 787 MHz with a channel spacing
of 2 MHz according to IEEE 802.15.4c-2009. Center frequencies are 780, 782, 784,
and 786 MHz.
Additionally, the PLL supports all frequencies from 769 to 935 MHz with 1 MHz
frequency spacing and 3 bands with 100 kHz spacing from 769.0 to 794.5 MHz, 857.0
to 882.5 MHz, and 903.0 to 928.5 MHz.
The frequency is selected by register bits CC_BAND of register 0x14 (CC_CTRL_1)
and register bits CC_NUMBER of register 0x13 (CC_CTRL_0).
Table 7-35 shows the
settings of CC_BAND and CC_NUMBER.
Table 7-35. Frequency Bands and Numbers
CC_BAND
CC_NUMBER
Description
0
Not used
European and North American channels according to IEEE
802.15.4-2003/2006; Frequency selected by register bits
CHANNEL (register 0x08, PHY_CC_CCA), refer to section
1
0 – 255
769.0 – 794.5 MHz; Fc [MHz] = 769.0 + 0.1 CC_NUMBER
2
0 – 255
857.0 – 882.5 MHz; Fc [MHz] = 857.0 + 0.1 CC_NUMBER
3
0 – 255
903.0 – 928.5 MHz; Fc [MHz] = 903.0 + 0.1 CC_NUMBER
4
0 – 94
769 – 863 MHz; Fc [MHz] = 769 + CC_NUMBER
5
0 – 102
833 – 935 MHz; Fc [MHz] = 833 + CC_NUMBER
6, 7
0 – 255
Reserved