The MAX7057 frequency-programmable UHF transmitter
is designed to transmit ASK/FSK data at a wide
range of frequencies from 300MHz to 450MHz. The
MAX7057 has internal tuning capacitors at the output of
the power amplifier that are programmable for matching
to an antenna or load. This allows the user to
change to a new frequency and match the antenna at
the new frequency simultaneously. The MAX7057 transmits
at a data rate up to 100kbps nonreturn-to-zero
(NRZ) (50kbps Manchester coded). Typical transmitted
power into a 50Ω load is +9.2dBm with a +2.7V supply.
The device operates from +2.1V to +3.6V and typically
draws under 12.5mA of current in FSK mode (8.5mA in
ASK mode) when the antenna-matching network is
designed to operate over the 315MHz to 433.92MHz
frequency range. For narrower operating frequency
ranges, the matching network can be redesigned to
improve efficiency. The standby current is less than
1μA at room temperature.
The MAX7057 reference frequency from the crystal
oscillator is multiplied by a fully integrated fractional-N
phase-locked loop (PLL). The multiplying factor of the
PLL is set by a 16-bit number, with 4 bits for integer
and 12 bits for fraction; the multiplying factor can be
anywhere between 19 and 28. The 12-bit fraction in the
synthesizer sets a tuning resolution equal to the reference
frequency divided by 4096; frequency deviation
can be set as low as ±2kHz and as high as ±100kHz.
The fractional-N synthesizer eliminates the problems
associated with oscillator-pulling FSK signal generation.
The MAX7057 has a serial peripheral interface (SPI?)
for selecting all the necessary settings.
The MAX7057 is available in a 16-pin SO package and
is specified to operate in the -40°C to +125°C automotive
temperature range.
Applications
RF Remote Controls
Garage Door Openers
Home Automation
Automotive
Wireless Sensors
Wireless Game Consoles
Wireless Computer Peripherals
Security Systems