si4430 Silicon Laboratories, si4430 Datasheet - Page 15

• Manufacturer Part Number: si4430
• Description: Si4430 Ism Transceiver
• Manufacturer: Silicon Laboratories

2. Functional Description
The Si4430 is a 100% CMOS ISM wireless transceiver
with continuous frequency tuning over the complete
900–960 MHz band. The wide operating voltage range
of 1.8–3.6 V and low current consumption makes the
Si4430
applications.
The Si4430 operates as a time division duplexing (TDD)
transceiver where the device alternately transmits and
receives data packets. The device uses a single-
conversion, image-reject mixer to downconvert the 2-
level FSK/GFSK/OOK modulated receive signal to a low
IF frequency. Following a programmable gain amplifier
(PGA) the signal is converted to the digital domain by a
high
demodulation, slicing, error correction, and packet
handling to be performed in the built-in DSP increasing
the receiver’s performance and flexibility versus analog
based architectures. The demodulated signal is then
output to the system MCU through a programmable
GPIO or via the standard SPI bus by reading the 64-
byte RX FIFO.
A single high precision local oscillator (LO) is used for
both transmit and receive modes since the transmitter
and receiver do not operate at the same time. The LO is
generated by an integrated VCO and  Fractional-N
PLL synthesizer. The synthesizer is designed to support
configurable data rates, output frequency, frequency
deviation, and Gaussian filtering at any frequency
between 900–960 MHz. The transmit FSK data is
modulated directly into the  data stream and can be
shaped by a Gaussian low-pass filter to reduce
unwanted spectral content.
The PA output power can be configured between –8
and +13 dBm in 3 dB steps. The PA is single-ended to
allow for easy antenna matching and low BOM cost.
The PA incorporates automatic ramp-up and ramp-
down control to reduce unwanted spectral spreading.
The Si4430 supports frequency hopping, TX/RX switch
control, and antenna diversity switch control to extend
the link range and improve performance. Antenna
diversity is completely integrated into the Si4430 and
can improve the system link budget by 8–10 dB,
resulting in substantial range increases depending on
the environmental conditions.
The Si4430 is designed to work with a microcontroller,
crystal, and a few passives to create a very low cost
system as shown Figure 1. Voltage regulators are
integrated on-chip which allow for a wide range of
operating supply voltage conditions from +1.8 to +3.6 V.
A standard 4-pin SPI bus is used to communicate with
the microcontroller. Three configurable general purpose
performance
and
ideal solution

ADC
for
allowing
battery powered
Preliminary Rev. 0.4
filtering,
I/Os are available for use to tailor towards the needs of
the system. A more complete list of the available GPIO
functions is shown in "8. Auxiliary Functions" on page
53 but just to name a few, microcontroller clock output,
Antenna Diversity, POR, and specific interrupts. A
limited number of passive components are needed to
match the LNA and PA.
The application shown in Figure 1 is designed for a
system with an TX/RX direct-tie configuration without
the use of a TX/RX switch. Most lower power
applications will use this configuration. A direct-tie
reference design is available from Silicon Laboratories
applications support.
For applications seeking improved performance in the
presence of multipath fading antenna diversity can be
used. Antenna diversity includes a switch to select the
optimal antenna between a pair of antennas for
improved performance. The Antenna Diversity Control
Algorithm is completely integrated into the chip and is
discussed further in Figure 24 on page 55. A complete
Antenna Diversity reference design is available from
Silicon Laboratories applications support.
An application example with a separate RX and TX
antenna is shown in Figure 31, “Split RF I/Os with
Separated TX and RX Connectors—Schematic,” on
page 67. This example is used for testing of the TX and
RX paths in a lab environment and shows, conceptually,
the matching of the TX and RX antennas.
Si4430
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