SI4421 Datasheet, PDF (1/46 Pages) Silicon Laboratories – Fully integrated

Si4421 Universal ISM Band
FSK Transceiver
DESCRIPTION
Silicon Labs’ Si4421 is a single chip, low power, multi-channel FSK
transceiver designed for use in applications requiring FCC or ETSI
conformance for unlicensed use in the 433, 868 and 915 MHz bands.
The Si4421 transceiver is a part of Silicon Labs’ EZRadio^TM product
line, which produces a flexible, low cost, and highly integrated solution
that does not require production alignments. The chip is a complete
analog RF and baseband transceiver including a multi-band PLL
synthesizer with PA, LNA, I/Q down converter mixers, baseband filters
and amplifiers, and an I/Q demodulator. All required RF functions are
integrated. Only an external crystal and bypass filtering are needed for
operation.
The Si4421 features a completely integrated PLL for easy RF design,
and its rapid settling time allows for fast frequency-hopping, bypassing
multipath fading and interference to achieve robust wireless links. The
PLL’s high resolution allows the usage of multiple channels in any of
the bands. The receiver baseband bandwidth (BW) is programmable to
accommodate various deviation, data rate and crystal tolerance
requirements. The transceiver employs the Zero-IF approach with I/Q
demodulation. Consequently, no external components (except crystal
and decoupling) are needed in most applications.
The Si4421 dramatically reduces the load on the microcontroller with
the integrated digital data processing features: data filtering, clock
recovery, data pattern recognition, integrated FIFO and TX data
register. The automatic frequency control (AFC) feature allows the use
of a low accuracy (low cost) crystal. To minimize the system cost, the
Si4421 can provide a clock signal for the microcontroller, avoiding the
need for two crystals.
For low power applications, the Si4421 supports low duty cycle
operation based on the internal wake-up timer.
FUNCTIONAL BLOCK DIAGRAM
RF1 13
RF2 12
LNA
PA
MIX
I
AMP OC
MIX
Q
Self cal.
AMP OC
RF Parts
PLL & I/Q VCO
with cal.
RSSI
BB Amp/Filt./Limiter
I/Q
DEMOD
COMP
DQD
AFC
clk
Data Filt
CLK Rec ^data
FIFO
7
DCLK /
CFIL /
FFIT /
FSK /
6 _{DATA /}
nFFS
Data processing units
CLK div
8
CLK
Xosc
9
XTL /
REF
WTM
with cal.
LBD
Low Power parts
Controller
Bias
15 1
ARSSI SDI
2
3
4
SCK nSEL SDO
5
10
16
nIRQ nRES nINT /
VDI
11 14
VSS VDD
Si4421
PIN ASSIGNMENT
SDI
SCK
nSEL
SDO
nIRQ
FSK / DATA / nFFS
DCLK / CFIL / FFIT
CLK
nINT / VDI
ARSSI
VDD
RF1
RF2
VSS
nRES
XTL / REF
This document refers to Si4421-IC rev A1.
See www.silabs.com/integration for any applicable errata.
See back page for ordering information.
FEATURES
 Fully integrated (low BOM, easy design-in)
 No alignment required in production
 Fast-settling, programmable, high-resolution PLL synthesizer
 Fast frequency-hopping capability
 High bit rate (up to 115.2 kbps in digital mode and 256 kbps
in analog mode)
 Direct differential antenna input/output
 Integrated power amplifier
 Programmable TX frequency deviation (15 to 240 kHz)
 Programmable RX baseband bandwidth (67 to 400 kHz)
 Analog and digital RSSI outputs
 Automatic frequency control (AFC)
 Data quality detection (DQD)
 Internal data filtering and clock recovery
 RX synchron pattern recognition
 SPI compatible serial control interface
 Clock and reset signals for microcontroller
 16-bit RX Data FIFO
 Two 8-bit TX data registers
 Low power duty cycle mode
 Standard 10 MHz crystal reference with on-chip tuning
 Wake-up timer
 2.2 to 3.8 V supply voltage
 Low power consumption
 Low standby current (0.3 A)
 Compact 16 pin TSSOP package
 Supports very short packets (down to 3 bytes)
 Excellent temperature stability of the RF parameters
 Good adjacent channel rejection/blocking
TYPICAL APPLICATIONS
 Home security and alarm
 Remote control, keyless entry
 Wireless keyboard/mouse and other PC peripherals
 Toy controls
 Remote keyless entry
 Tire pressure monitoring
 Telemetry
 Personal/patient data logging
 Remote automatic meter reading
Si4421-DS rev 2.4r 0708
1
www.silabs.com