MICRF505L
850MHz and 950MHz ISM Band
Transceiver
MLF and MicroLead Frame is a registered trademark of Amkor Technologies
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
August 2006 1
M9999-092904
+1 408-944-0800
General Description
The MICRF505 is a true single-chip, frequency shift
keying (FSK) transceiver intended for use in half-
duplex, bidirectional RF links. The multi-channeled
FSK transceiver is intended for UHF radio
equipment in compliance with the with the North
American Federal Communications Commission
(FCC) part 15.247 and the European
Telecommunication Standard Institute (ETSI)
specification, EN300 220.
The transmitter consists of a PLL frequency
synthesizer and 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 output power of
the power amplifier can be programmed to seven
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 which makes channel filtering possible with low-
power, integrated low-pass filters. The receiver
consists of a low noise amplifier (LNA) that drives a
quadrature mix pair. The mixer outputs feed two
identical signal channels in phase quadrature. Each
channel includes a pre-amplifier, a third order
Sallen-Key RC low-pass filter that protects the
following switched-capacitor filter from strong
adjacent channel signals, and a limiter. The main
channel filter is a switched-capacitor implementation
of a six-pole elliptic low pass filter. The cut-off
frequency of the Sallen-Key RC filter can be
programmed to four different frequencies: 100kHz,
150kHz, 230kHz, and 340kHz. The I and Q channel
outputs are demodulated and produce a digital data
output. The demodulator detects the relative phase
of the I and the Q channel signal. If the I channel
signal lags behind the Q channel, the FSK tone
frequency is above the LO frequency (data '1'). If the
I channel leads the Q channel, the FSK tone is
below the LO frequency (data '0'). The output of the
receiver is available on the DataIXO pin. A receive
signal strength indicator (RSSI) circuit indicates the
received signal level. All support documentation can
be found on Micrel’s web site at www.micrel.com.
RadioWire®
Features
• True single chip transceiver
• Digital bit synchronizer
• Received signal strength indicator (RSSI)
• RX and TX power management
• Power down function
• Reference crystal tuning capabilities
• Frequency error estimator
• Baseband shaping
• Three-wire programmable serial interface
• Register read back function
Applications
• Telemetry
• Remote metering
• Wireless controller
• Remote data repeater
• Remote control systems
• Wireless modem
• Wireless security system
