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參數(shù)資料
| 型號： | LM3207 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | DC/DC變換器 |
| 英文描述： | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers with Integrated Vref LDO |
| 中文描述： | 六百五十零毫安微型，可調(diào)，降壓型DC -射頻功率放大器DC轉(zhuǎn)換器集成Vref的穩(wěn)壓器 |
| 文件頁數(shù)： | 14/19頁 |
| 文件大?。?/td> | 1335K |
| 代理商： | LM3207 |
Operation Description
The LM3207 is a simple, step-down DC-DC converter with a
VREF LDO optimized for powering RF power amplifiers
(PAs) in mobile phones, portable communicators, and similar
battery powered RF devices. The DC-DC converter is de-
signed to allow the RF PA to operate at maximum efficiency
over a wide range of power levels from a single Lithium-Ion
battery cell. The DC-DC is based on current-mode buck
architecture, with synchronous rectification for high effi-
ciency. It is designed for a maximum load capability of
650mA in PWM mode.
Maximum load range may vary from this depending on input
voltage, output voltage and the inductor chosen.
The device has two pin-selectable operating modes required
for powering RF PAs in mobile phones and other sophisti-
cated portable devices. Fixed-frequency PWM operation of-
fers regulated output at high efficiency while minimizing in-
terference with sensitive IF and data acquisition circuits.
Shutdown mode turns the device off and reduces battery
consumption to 0.01uA (typ).
Efficiency is typically around 95% for a 400mA load with
3.9V
IN
, 3.4V
OUT
. The output voltage is dynamically program-
mable from 0.8V (typ) to 3.6V (typ) by adjusting the voltage
on the control pin without the need for external feedback
resistors. This ensures longer battery life by being able to
change the PA supply voltage dynamically depending on its
transmitting power.
Additional features include current overload protection, and
thermal overload shutdown.
The LM3207 is constructed using a chip-scale 9-pin micro
SMD package. This package offers the smallest possible
size, for space-critical applications such as cell phones,
where board area is an important design consideration. Use
of a high switching frequency (2MHz) reduces the size of
external components. As shown in
Figure 1
, only four exter-
nal power components are required for implementation. Use
of a micro SMD package requires special design consider-
ations for implementation. (See Micro SMD PackageAssem-
bly and use in the Applications Information section.) The fine
bump-pitch requires careful board design and precision as-
sembly equipment. Use of this package is best suited for
opaque-case applications, where its edges are not subject to
high-intensity ambient red or infrared light. Also, the system
controller should set EN low during power-up and other low
supply voltage conditions. (See Shutdown Mode in the De-
vice Information section.)
Circuit Operation (DC-DC
Converter)
Referring to
Figure 1
and
Figure 2
, the LM3207 operates as
follows. During the first part of each switching cycle, the
control block in the LM3207 turns on the internal PFET
(P-channel MOSFET) switch. This allows current to flow
from the input through the inductor to the output filter capaci-
tor and load. The inductor limits the current to a ramp with a
slope of around (PV
- V
) / L, by storing energy in a
magnetic field. During the second part of each cycle, the
controller turns the PFET switch off, blocking current flow
from the input, and then turns the NFET (N-channel MOS-
FET) synchronous rectifier on. In response, the inductor’s
magnetic field collapses, generating a voltage that forces
current from ground through the synchronous rectifier to the
output filter capacitor and load. As the stored energy is
transferred back into the circuit and depleted, the inductor
current ramps down with a slope around V
OUT
/ L. The
output filter capacitor stores charge when the inductor cur-
rent is high, and releases it when low, smoothing the voltage
across the load.
The output voltage is regulated by modulating the PFET
switch on time to control the average current sent to the load.
The effect is identical to sending a duty-cycle modulated
rectangular wave formed by the switch and synchronous
rectifier at SW to a low-pass filter formed by the inductor and
output filter capacitor. The output voltage is equal to the
average voltage at the SW pin.
PWM Operation
While in PWM (Pulse Width Modulation) mode, the output
voltage is regulated by switching at a constant frequency
and then modulating the energy per cycle to control power to
the load. Energy per cycle is set by modulating the PFET
switch on-time pulse width to control the peak inductor cur-
rent. This is done by comparing the signal from the current-
sense amplifier with a slope compensated error signal from
the voltage-feedback error amplifier. At the beginning of
20165336
FIGURE 3. Typical Application Circuit
L
www.national.com
14
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM3207TL | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers with Integrated Vref LDO |
| LM3207TLX | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers with Integrated Vref LDO |
| LM3208 | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers |
| LM3208TL | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers |
| LM3208TLX | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3207_07 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers with Integrated Vref LDO |
| LM3207TL | 制造商:Texas Instruments 功能描述:LDO DC/DC CONVERTER POWERWISE 3207 |
| LM3207TL/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM3207TL-2.53 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers with Integrated Vref LDO |
| LM3207TL-2.53/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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