300MHz-to-450MHz Low-Power,
Crystal-Based ASK Transmitter
Pin Description
PIN
1
2
3
4
5
6
7
8
NAME
XTAL1
GND
PAGND
PAOUT
ENABLE
DATA
V DD
XTAL2
FUNCTION
1st Crystal Input. f RF = 32 x f XTAL .
Ground. Connect to system ground.
Ground for the Power Amplifier (PA). Connect to system ground.
Power-Amplifier Output. This output requires a pullup inductor to the supply voltage, which may be part
of the output-matching network to a 50 ? antenna.
Standby/Power-Up Input. A logic low on ENABLE places the device in standby mode.
OOK Data Input. Power amplifier is ON when DATA is high.
Supply Voltage. Bypass to GND with capacitor as close to the pin as possible.
2nd Crystal Input. f RF = 32 x f XTAL .
Detailed Description
The MAX1472 is a highly integrated OOK/ASK transmit-
ter operating over the 300MHz to 450MHz frequency
range. The IC includes a complete PLL and a highly
efficient PA. The device can also be easily placed into
a 5nA low-power shutdown mode.
Shutdown Mode
The ENABLE pin is internally pulled down with a 15μA
current source. If the pin is left unconnected or pulled
low, the MAX1472 goes into shutdown mode, where the
supply current drops to less than 5nA. When ENABLE
is high, the IC is enabled and is ready for transmission
after 220μs (frequency settles to within 50kHz).
The 220μs turn-on time of the MAX1472 is mostly domi-
nated by the crystal oscillator startup time. Once the
oscillator is running, the 1.6MHz PLL loop bandwidth
allows fast-frequency recovery during power-amplifier
toggling.
Phase-Locked Loop
The PLL block contains a phase detector, charge
pump, integrated loop filter, VCO, 32X clock divider,
and crystal oscillator. This PLL requires no external
components, other than a crystal. The relationship
between the carrier and crystal frequency is given by:
f XTAL = f RF / 32
The lock-detect circuit prevents the PA from transmit-
ting until the PLL is locked. In addition, the device shuts
down the PA if the reference frequency is lost.
6
Power Amplifier (PA)
The PA of the MAX1472 is a high-efficiency, open-drain,
switch-mode amplifier. With proper output matching net-
work, the PA can drive a wide range of impedances,
including the small-loop PC board trace antenna and
any 50 ? antenna. The output-matching network for a
50 ? antenna is shown in the Typical Application Circuit.
The output-matching network suppresses the carrier har-
monics and transforms the antenna impedance to an
optimal impedance at PAOUT (pin 4), which is between
100 ? and 150 ? for a 2.7V supply.
When the output matching network is properly tuned,
the PA transmits power with high efficiency. The Typical
Application Circuit delivers 10.3dBm at 2.7V supply with
9.1mA of supply current. Thus, the overall efficiency is
44%. The efficiency of the PA itself is more than 52%.
Applications Information
Output Power Adjustment
It is possible to adjust the output power down to
-10dBm with the addition of a resistor. The addition of
the power-adjust resistor also reduces power con-
sumption. See the Supply Current and Output Power
vs. External Resistor and Supply Current vs. Output
Power graphs in the Typical Operating Characteristics
section. It is imperative to add both a low-frequency
and a high-frequency decoupling capacitor as shown
in the Typical Application Circuit.
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相关代理商/技术参数
MAX1473ETJ 制造商:Maxim Integrated Products 功能描述:315MHZ/433MHZ ASK SUPERHETERODYNE RECEIVER WI - Rail/Tube
MAX1473ETJ+ 功能描述:射频接收器 315MHz/434MHz Superheterodyne Rcvr RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel
MAX1473ETJ+T 功能描述:射频接收器 315MHz/434MHz Superheterodyne Rcvr RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel
MAX1473ETJ-T 制造商:Maxim Integrated Products 功能描述:315MHZ/433MHZ ASK SUPERHETERODYNE RECEIVER WI - Tape and Reel
MAX1473EUI 功能描述:射频接收器 RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel
MAX1473EUI/V+ 功能描述:射频接收器 315MHz/434MHz Superheterodyne Rcvr RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel
MAX1473EUI/V+T 功能描述:射频接收器 315MHz/434MHz Superheterodyne Rcvr RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel
MAX1473EUI+ 功能描述:射频接收器 315MHz/434MHz Superheterodyne Rcvr RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel