MICRF500 Datasheet, PDF (1/18 Pages) Micrel Semiconductor – 700MHz to 1.1GHz RadioWire RF Transceiver

MICRF500
Micrel
MICRF500
700MHz to 1.1GHz RadioWire™ RF Transceiver
Final
General Description
The MICRF500 is a single chip UHF transceiver designed for
spread spectrum communication (FHSS) intended for ISM
(Industrial, Scientific and Medical) and SRD (Short Range
Device) frequency bands from 700MHz to 1100MHz with
FSK data rates up to 128k baud.
The transmitter consists of a PLL frequency synthesizer and
a power amplifier. The frequency synthesizer consists of a
voltage-controlled oscillator (VCO), a crystal oscillator, dual-
modulus prescaler, programmable frequency dividers and a
phase-detector. The loop filter is external for flexibility and
can be a simple passive circuit. The VCO is a Colpitts
oscillator which requires an external resonator and varactor.
FSK modulation can be applied externally to the VCO. The
synthesizer has two different N, M and A frequency dividers.
FSK modulation can also be implemented by switching
between these dividers (max. 2400bps). The lengths of the N
and M and A registers are 12, 10 and 6 bits respectively. For
all types of FSK modulation, data is entered at the DATAIXO
pin (see application circuit). The output power of the power
amplifier can be programmed to eight levels. A lock detect
circuit detects when the PLL is in lock.
In receive mode the PLL synthesizer generates the local
oscillator (LO) signal. The N, M and A values that give the LO
frequency are stored in the N0, M0 and A0 registers. The
receiver is a zero intermediate frequency (IF) type in order to
make channel filtering possible with low-power integrated
low-pass filters. The receiver consists of a low-noise amplifier
(LNA) that drives a quadrature mixer pair. The mixer outputs
feed two identical signal channels in phase quadrature. Each
channel includes a preamplifier, a third order Sallen-Key RC
low pass filter that protects the following gyrator filter from
strong adjacent channel signals and finally, a limiter. The
main channel filter is a gyrator capacitor implementation of a
seven-pole elliptic low pass filter. The elliptic filter minimizes
the total capacitance required for a given selectivity and
dynamic range. The cut-off frequency of the Sallen-Key RC
filter can be programmed to four different frequencies: 10kHz,
30kHz, 60kHz and 200kHz. An external resistor adjusts the
cut-off frequency of the gyrator filter. The demodulator de-
modulates the I and Q channel outputs and produces a digital
data output. It detects the relative phase of the I and the Q
channel signal. If the I channel signal lags the Q channel, the
FSK tone frequency lies above the LO frequency (data ‘1’). If
the I channel leads the Q channel, the FSK tone lies below the
LO frequency (data ‘0’). The output of the receiver is available
on the DATAIXO pin. A RSSI (Receive Signal Strength
Indicator) circuit indicates the received signal level.
RadioWire™
A two pin serial interface is used to program the circuit.
External components are necessary for RF input and output
impedance matching and decoupling of power. Other exter-
nal components are the VCO resonator circuit with varactor,
crystal, feedback capacitors and components for FSK modu-
lation with the VCO, loop filter, bias resistors for the power
amplifier and gyrator filters. A T/R switch can be implemented
with 2-pin diodes. This gives maximum input sensitivity and
transmit output power.
Features
• Frequency range: 700MHz to 1100MHz
• Modulation: FSK
• RF output power: 10dBm
• Sensitivity (19.2k bauds, BER=10^-3): –104dBm
• Maximum data rate: 128k bauds
Applications
• Telemetry
• Remote metering
• Wireless controller
• Wireless data repeaters
• Remote control systems
• Wireless modem
• Wireless security system
Ordering Information
Part Number Ambient Temp. Range
MICRF500BLQ
–40°C to +85°C
Package
44-Lead LQFP
RadioWire is a trademark of Micrel, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com
March 2003
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MICRF500