SI4431-B1-FMR Silicon Laboratories Inc, SI4431-B1-FMR Datasheet - Page 25

• Manufacturer Part Number: SI4431-B1-FMR
• Description: IC TXRX 240-930MHZ -8-13DB 20QFN
• Manufacturer: Silicon Laboratories Inc

Specifications of SI4431-B1-FMR

• Mfg Application Notes: Transitioning SI4430/31 to Rev B
• Frequency: 240MHz ~ 930MHz
• Data Rate - Maximum: 256kbps
• Modulation Or Protocol: FSK, GFSK, OOK
• Applications: General Purpose
• Power - Output: 13dBm
• Sensitivity: -121dBm
• Voltage - Supply: 1.8 V ~ 3.6 V
• Current - Receiving: 18.5mA
• Current - Transmitting: 30mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-VQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -

3.5. Frequency Control
For calculating the necessary frequency register settings it is recommended that customers use Silicon Labs’
Wireless Design Suite (WDS) or the EZRadioPRO Register Calculator worksheet (in Microsoft Excel) available on
the product website. These methods offer a simple method to quickly determine the correct settings based on the
application requirements. The following information can be used to calculated these values manually.
3.5.1. Frequency Programming
In order to receive or transmit an RF signal, the desired channel frequency, f
Si4430/31/32. The Si4431/32 and Si4430 cover different frequencies. This section discusses the frequency range
covered by all EZRadioPRO devices. Note that this frequency is the center frequency of the desired channel and
not an LO frequency. The carrier frequency is generated by a Fractional-N Synthesizer, using 10 MHz both as the
reference frequency and the clock of the (3
accumulators. This design was made to obtain the desired frequency resolution of the synthesizer. The overall
division ratio of the feedback loop consist of an integer part (N) and a fractional part (F).In a generic sense, the
output frequency of the synthesizer is as follows:
The fractional part (F) is determined by three different values, Carrier Frequency (fc[15:0]), Frequency Offset
(fo[8:0]), and Frequency Deviation (fd[7:0]). Due to the fine resolution and high loop bandwidth of the synthesizer,
FSK modulation is applied inside the loop and is done by varying F according to the incoming data; this is
discussed further in "3.5.4. Frequency Deviation" on page 27. Also, a fixed offset can be added to fine-tune the
carrier frequency and counteract crystal tolerance errors. For simplicity assume that only the fc[15:0] register will
determine the fractional component. The equation for selection of the carrier frequency is shown below:
The integer part (N) is determined by fb[4:0]. Additionally, the output frequency can be halved by connecting a ÷2
divider to the output. This divider is not inside the loop and is controlled by the hbsel bit in "Register 75h.
Frequency Band Select." This effectively partitions the entire 240–960 MHz frequency range into two separate
bands: High Band (HB) for hbsel = 1, and Low Band (LB) for hbsel = 0. The valid range of fb[4:0] is from 0 to 23. If
a higher value is written into the register, it will default to a value of 23. The integer part has a fixed offset of 24
added to it as shown in the formula above. Table 12 demonstrates the selection of fb[4:0] for the corresponding
frequency band.
After selection of the fb (N) the fractional component may be solved with the following equation:
fb and fc are the actual numbers stored in the corresponding registers.
Add R/W Function/Description
73
74
75
76
77
R/W
R/W
R/W Frequency Band Select
R/W
R/W
Frequency Offset 1
Frequency Offset 2
Nominal Carrier
Nominal Carrier
Frequency 1
Frequency 0
fc
f
[
15
TX
:

] 0
10
fc[15]

fo[7]
fc[7]
MHz
f
D7
carrier

 

10
MHz
( *

f
OUT
10
hbsel
sbsel
fc[14]
fo[6]
fc[6]
D6
( *
MHz
rd
f

TX
hbsel
10
order) ΔΣ modulator. This modulator uses modulo 64000

Rev 1.1
) 1
MHz

(
( *
fc[13]
hbsel
fo[5]
fc[5]
hbsel

D5
) 1
fb

[
(

: 4
N

fb
) 1
] 0

fc[12]
[
fo[4]
fb[4]
fc[4]
D4
: 4
F


(
)
24
] 0
N



24
F
fc
fc[11]
fo[3]
fb[3]
64000
fc[3]
)
D3
Si4430/31/32-B1
[

 

carrier
15
*
64000
:
] 0
, must be programmed into the
)
fc[10]
fo[2]
fb[2]
fc[2]
D2
fo[1] fo[0]
fo[9] fo[8]
fb[1] fb[0]
fc[9] fc[8]
fc[1] fc[0]
D1
D0 POR Def.
BBh
00h
00h
35h
80h
25