SPIRIT1QTR Datasheet, PDF (43/101 Pages) List of Unclassifed Manufacturers – Low data rate, low power sub-1GHZ transceiver

SPIRIT1
Block description
Table 26. CP word look-up (continued)
Channel frequency
817.0
827.7
838.3
849.2
860.2
872.0
883.8
908.0
919.8
932.0
943.8
827.7
838.3
849.2
860.2
872.0
883.8
895.8
919.8
932.0
943.8
956.0
WCP [2:0]
100
101
110
111
000
001
010
100
101
110
111
The SPIRIT1 is provided with an automatic and very fast calibration procedure for the
frequency synthesizer. If not disabled, it is performed each time the SYNTH is required to
lock to the programmed RF channel frequency (i.e. from READY to LOCK/TX/RX or from
RX to TX and vice versa). Calibration time is 54 μs.
After completion, the calibration word is used automatically by the SPIRIT1 and is stored in
the RCO_VCO_CALIBR_OUT[1:0] registers.
In order to get the synthesizer locked when the calibration procedure is not enabled, the
correct calibration words to be used must be previously stored in the
RCO_VCO_CALIBR_IN[2:0] registers using VCO_CALIBR_TX and VCO_CALIBR_RX
fields for TX and RX modes respectively.
The advantage of performing an offline calibration is that the LOCK/setting time is roughly
20 μs (using proper VCO_CALIBR_TX/RX register values).
It recommended set the T split time at the longest value (3.47 ns) to facilitate the calibrator
operation, SEL_TSPLIT field of the register SYNTH_CONFIG[0] (register address 0x9F) at
1.
If calibration is enabled, the LOCK/setting time is approximately 80 μs.
8.6
RCO: features and calibration
The SPIRIT1 contains an ultra-low power RC oscillator capable of generating 34.7 kHz with
both 24 MHz and 26 MHz; the RC oscillator frequency is calibrated comparing it against the
digital domain clock fCLK divided by 692 or 750, respectively. The configuration bit, called
24_26MHz_SELECT in the ANA_FUNC_CONF register, contains the information of the
calibrator about the frequency of the crystal under operation. If the digital domain clock is 25
MHz, the setting of the configuration bit 24_26MHz_SELECT will calibrate the low power
RC oscillator according to the following table:
DocID022758 Rev 5
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