Datasheet MAX1472 (Maxim) - 6
| 制造商 | Maxim |
| 描述 | 300MHz-to-450MHz Low-Power, Crystal-Based ASK Transmitter |
| 页数 / 页 | 9 / 6 — 300MHz-to-450MHz Low-Power, Crystal-Based ASK Transmitter. Pin … |
| 文件格式/大小 | PDF / 169 Kb |
| 文件语言 | 英语 |
300MHz-to-450MHz Low-Power, Crystal-Based ASK Transmitter. Pin Description. PIN. NAME. FUNCTION. MAX1472. Detailed Description
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300MHz-to-450MHz Low-Power, Crystal-Based ASK Transmitter Pin Description PIN NAME FUNCTION
1 XTAL1 1st Crystal Input. fRF = 32 x fXTAL. 2 GND Ground. Connect to system ground. 3 PAGND 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
MAX1472
4 PAOUT of the output-matching network to a 50Ω antenna. 5 ENABLE Standby/Power-Up Input. A logic low on ENABLE places the device in standby mode. 6 DATA OOK Data Input. Power amplifier is ON when DATA is high. 7 VDD Supply Voltage. Bypass to GND with capacitor as close to the pin as possible. 8 XTAL2 2nd Crystal Input. fRF = 32 x fXTAL.
Detailed Description Power Amplifier (PA)
The PA of the MAX1472 is a high-efficiency, open-drain, The MAX1472 is a highly integrated OOK/ASK transmit- switch-mode amplifier. With proper output matching net- ter operating over the 300MHz to 450MHz frequency work, the PA can drive a wide range of impedances, range. The IC includes a complete PLL and a highly including the small-loop PC board trace antenna and efficient PA. The device can also be easily placed into any 50Ω antenna. The output-matching network for a a 5nA low-power shutdown mode. 50Ω antenna is shown in the Typical Application Circuit.
Shutdown Mode
The output-matching network suppresses the carrier har- The ENABLE pin is internally pulled down with a 15µA monics and transforms the antenna impedance to an current source. If the pin is left unconnected or pulled optimal impedance at PAOUT (pin 4), which is between low, the MAX1472 goes into shutdown mode, where the 100Ω and 150Ω for a 2.7V supply. supply current drops to less than 5nA. When ENABLE When the output matching network is properly tuned, is high, the IC is enabled and is ready for transmission the PA transmits power with high efficiency. The Typical after 220µs (frequency settles to within 50kHz). Application Circuit delivers 10.3dBm at 2.7V supply with The 220µs turn-on time of the MAX1472 is mostly domi- 9.1mA of supply current. Thus, the overall efficiency is nated by the crystal oscillator startup time. Once the 44%. The efficiency of the PA itself is more than 52%. oscillator is running, the 1.6MHz PLL loop bandwidth
Applications Information
allows fast-frequency recovery during power-amplifier toggling.
Output Power Adjustment
It is possible to adjust the output power down to
Phase-Locked Loop
-10dBm with the addition of a resistor. The addition of The PLL block contains a phase detector, charge the power-adjust resistor also reduces power con- pump, integrated loop filter, VCO, 32X clock divider, sumption. See the Supply Current and Output Power and crystal oscillator. This PLL requires no external vs. External Resistor and Supply Current vs. Output components, other than a crystal. The relationship Power graphs in the Typical Operating Characteristics between the carrier and crystal frequency is given by: section. It is imperative to add both a low-frequency fXTAL = fRF / 32 and a high-frequency decoupling capacitor as shown The lock-detect circuit prevents the PA from transmit- in the Typical Application Circuit. ting until the PLL is locked. In addition, the device shuts down the PA if the reference frequency is lost.
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1 XTAL1 1st Crystal Input. fRF = 32 x fXTAL. 2 GND Ground. Connect to system ground. 3 PAGND 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
MAX1472
4 PAOUT of the output-matching network to a 50Ω antenna. 5 ENABLE Standby/Power-Up Input. A logic low on ENABLE places the device in standby mode. 6 DATA OOK Data Input. Power amplifier is ON when DATA is high. 7 VDD Supply Voltage. Bypass to GND with capacitor as close to the pin as possible. 8 XTAL2 2nd Crystal Input. fRF = 32 x fXTAL.
Detailed Description Power Amplifier (PA)
The PA of the MAX1472 is a high-efficiency, open-drain, The MAX1472 is a highly integrated OOK/ASK transmit- switch-mode amplifier. With proper output matching net- ter operating over the 300MHz to 450MHz frequency work, the PA can drive a wide range of impedances, range. The IC includes a complete PLL and a highly including the small-loop PC board trace antenna and efficient PA. The device can also be easily placed into any 50Ω antenna. The output-matching network for a a 5nA low-power shutdown mode. 50Ω antenna is shown in the Typical Application Circuit.
Shutdown Mode
The output-matching network suppresses the carrier har- The ENABLE pin is internally pulled down with a 15µA monics and transforms the antenna impedance to an current source. If the pin is left unconnected or pulled optimal impedance at PAOUT (pin 4), which is between low, the MAX1472 goes into shutdown mode, where the 100Ω and 150Ω for a 2.7V supply. supply current drops to less than 5nA. When ENABLE When the output matching network is properly tuned, is high, the IC is enabled and is ready for transmission the PA transmits power with high efficiency. The Typical after 220µs (frequency settles to within 50kHz). Application Circuit delivers 10.3dBm at 2.7V supply with The 220µs turn-on time of the MAX1472 is mostly domi- 9.1mA of supply current. Thus, the overall efficiency is nated by the crystal oscillator startup time. Once the 44%. The efficiency of the PA itself is more than 52%. oscillator is running, the 1.6MHz PLL loop bandwidth
Applications Information
allows fast-frequency recovery during power-amplifier toggling.
Output Power Adjustment
It is possible to adjust the output power down to
Phase-Locked Loop
-10dBm with the addition of a resistor. The addition of The PLL block contains a phase detector, charge the power-adjust resistor also reduces power con- pump, integrated loop filter, VCO, 32X clock divider, sumption. See the Supply Current and Output Power and crystal oscillator. This PLL requires no external vs. External Resistor and Supply Current vs. Output components, other than a crystal. The relationship Power graphs in the Typical Operating Characteristics between the carrier and crystal frequency is given by: section. It is imperative to add both a low-frequency fXTAL = fRF / 32 and a high-frequency decoupling capacitor as shown The lock-detect circuit prevents the PA from transmit- in the Typical Application Circuit. ting until the PLL is locked. In addition, the device shuts down the PA if the reference frequency is lost.
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