SPIRIT1 datasheet(39/94 Pages) STMICROELECTRONICS

39 / 94 page

SPIRIT1

Block description

Doc ID 022758 Rev 3

39/94

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

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:

795.3

806.0

010

806.0

817.0

011

817.0

827.7

100

827.7

838.3

101

838.3

849.2

110

849.2

860.2

111

860.2

872.0

000

872.0

883.8

001

883.8

895.8

010

908.0

919.8

100

919.8

932.0

101

932.0

943.8

110

943.8

956.0

111

Table 22.

CP word look-up (continued)

Channel frequency

WCP [2:0]

SPIRIT1 Datasheet(PDF) 39 Page - STMicroelectronics

SPIRIT1 Datasheet(HTML) 39 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94

Datasheet Download

Link URL