SX1231
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Table 9 Bit Rate Examples
BitRate
(15:8)
BitRate
(7:0)
(G)FSK
(G)MSK
Actual BR
(b/s)
Type
OOK
Classical modem baud rates
(multiples of 1.2 kbps)
0x68
0x34
0x1A
0x0D
0x06
0x03
0x01
0x00
0x02
0x01
0x0A
0x05
0x80
0x01
0x00
0x00
0x00
0x00
0x03
0x2B
0x15
0x0B
0x05
0x83
0x41
0xA1
0xD0
0x2C
0x16
0x00
0x00
0x00
0x40
0xD5
0xA0
0x80
0x6B
0xD1
1.2 kbps
2.4 kbps
1.2 kbps
2.4 kbps
4.8 kbps
9.6 kbps
19.2 kbps
1200.015
2400.060
4799.760
9600.960
19196.16
38415.36
76738.60
153846.1
57553.95
115107.9
12500.00
25000.00
50000.00
100000.0
150234.7
200000.0
250000.0
299065.4
32753.32
4.8 kbps
9.6 kbps
19.2 kbps
38.4 kbps
76.8 kbps
153.6 kbps
57.6 kbps
115.2 kbps
12.5 kbps
25 kbps
Classical modem baud rates
(multiples of 0.9 kbps)
Round bit rates
(multiples of 12.5, 25 and
50 kbps)
12.5 kbps
25 kbps
50 kbps
100 kbps
150 kbps
200 kbps
250 kbps
300 kbps
32.768 kbps
Watch Xtal frequency
32.768 kbps
3.4.3. FSK Modulation
FSK modulation is performed inside the PLL bandwidth, by changing the fractional divider ratio in the feedback loop of the
PLL. The large resolution of the sigma-delta modulator, allows for very narrow frequency deviation. The frequency
deviation FDEV is given by:
FDEV = FSTEP × Fdev(13,0)
To ensure a proper modulation, the following limit applies:
BR
2
-------
≤ 500kHz
FDEV
+
Note no constraint applies to the modulation index of the transmitter, but the frequency deviation must exceed 600 Hz.
3.4.4. OOK Modulation
OOK modulation is applied by switching on and off the Power Amplifier. Digital control and smoothing are available to
improve the transient power response of the OOK transmitter.
Rev 2 - Nov 2009
Page 20
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