Silicon Laboratories SI4421 manual Description, Functional Block Diagram, Features, Si4421

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’ EZRadioTM 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

		MIX	I	AMP	OC					7	DCLK /
											CFIL /
RF1	13					I/Q		Data Filt	clk		FFIT /
	LNA				Self cal.				data		FSK /
RF2						DEMOD		CLK Rec		6
	12	MIX									DATA /
			Q								nFFS
				AMP	OC
	PA							FIFO
		PLL & I/Q VCO			RSSI	COMP	DQD	AFC
		with cal.
	RF Parts		BB Amp/Filt./Limiter					Data processing units
	CLK div	Xosc	WTM		LBD		Controller		Bias
			with cal.
				Low Power parts

8 9 15 1 2 3 4 5 10 16 11 14

CLK	XTL /	ARSSI SDI SCK nSEL SDO nIRQ nRES nINT /	VSS VDD
	REF	VDI

Si4421

PIN ASSIGNMENT

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 μA)

∙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

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Si4421-DS rev 2.4r 0708	www.silabs.com