Si4020
3. Frequency Setting Command
bit
15
1
14
0
13
1
12
0
11
10
9
8
7
6
5
4
3
2
1
0
POR
f11 f10
f9
f8
f7
f6
f5
f4
f3
f2
f1
f0
A7D0h
The 12-bit parameter of the Frequency Setting Command
<f11 : f0> has the value F. The value F should be in the range
of 96 and 3903. When F is out of range, the previous value is
kept. The synthesizer center frequency f0 can be calculated as:
The constants C1 and C2 are determined by
the selected band as:
Band [MHz]
315
C1
1
C2
31
43
43
30
f0 = 10 MHz * C1 * (C2 + F/4000)
433
1
868
2
915
3
Note:
• For correct operation of the frequency synthesizer, the frequency and band of operation need to be programmed before the
synthesizer is started. Directly after activation of the synthesizer, the RF VCO is calibrated to ensure proper operation in the
programmed frequency band.
• When coding for the Si4020, it is suggested that recalibration routines be added to compensate for significant changes in
temperature and supply voltages.
4. Data Rate Command
bit
15
1
14
1
13
0
12
0
11
1
10
0
9
0
8
0
7
6
5
4
3
2
1
0
POR
r7
r6
r5
r4
r3
r2
r1
r0
C800h
In EEPROM mode the transmitted bit rate is determined by the 8-bit value R (bits <r7 : r0>) as:
BR = 10 MHz / 29 / (R+1)
Apart from setting custom values, the standard bit rates from 2.4 to 115.2 kbps can be approximated with minimal error.
The commands are read out with a different fixed bit rate:
Fsck = 10 MHz / 29 / 3 [~115.2 kHz]
5. Power Setting Command
bit
7
1
6
0
5
1
4
1
3
2
1
0
POR
B0h
ook
p2
p1
p0
The bit ook enables the OOK mode for the PA, in this case the data to be transmitted are received through the FSK pin.
p2 p1 p0 Relative Output Power [dB]
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
-3
-6
The output power is given in the table as relative to the
maximum available power, which depends on the actual
antenna impedance. (See: Antenna Application Note
available from www.silabs.com/integration).
-9
-12
-15
-18
-21
15
SILICON [ SILICON ]
