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參數(shù)資料
| 型號： | LM2706TL |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Miniature, Variable, Step-Down DC-DC Converter with Bypass for RF Power Amplifiers |
| 中文描述： | 0.75 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PBGA10 |
| 封裝： | MICRO BUMP, 10 PIN |
| 文件頁數(shù)： | 10/15頁 |
| 文件大?。?/td> | 451K |
| 代理商： | LM2706TL |
Circuit Operation
(Continued)
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
each cycle, the clock turns on the PFET switch, causing the
inductor current to ramp up. When the current sense signal
ramps past the error amplifier signal, the PWM comparator
turns off the PFET switch and turns on the NFET synchro-
nous rectifier, ending the first part of the cycle. If an increase
in load pulls the output down, the error amplifier output
increases, which allows the inductor current to ramp higher
before the comparator turns off the PFET. This increases the
average current sent to the output and adjusts for the in-
crease in the load.
Before going to the PWM comparator, the error signal is
summed with a slope compensation ramp from the oscillator
for stability of the current feedback loop. During the second
part of the cycle, a zero crossing detector turns off the NFET
synchronous rectifier if the inductor current ramps to zero.
The minimum on time of PFET in PWM mode is 200 ns.
Bypass Operation
The LM2706 contains an internal PFET switch for bypassing
the PWM DC-DC converter during Forced and Automatic
Bypass modes. In Forced Bypass mode, this switch is turned
on to power the PA directly from the battery for maximum RF
output power. Automatic Bypass mode turns on the bypass
switch when the input voltage approaches the programmed
output voltage so that the RF PA can continue to operate
with good linearity at high power levels when the battery
voltage is low. When the part operates in the Forced or
20040905
FIGURE 2. Simplified Functional Diagram
200409A7
FIGURE 3. Typical Circuit Waveforms in PWM Mode
L
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參數(shù)描述 |
|---|---|
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| LM2707MF | 制造商:Texas Instruments 功能描述:LED DRIVER WHITE POWERWISE SOT-23-8 |
| LM2707MF/NOPB | 功能描述:IC LED DRVR WHITE BCKLGT SOT23-8 RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動器 系列:- 標準包裝:1 系列:- 恒定電流:- 恒定電壓:- 拓撲:PWM，切換式電容器（充電泵） 輸出數(shù):1 內(nèi)部驅(qū)動器:是 類型 - 主要:背光 類型 - 次要:白色 LED 頻率:642kHz 電源電壓:2.7 V ~ 5.5 V 輸出電壓:5V 安裝類型:表面貼裝 封裝/外殼:10-VFDFN 裸露焊盤 供應商設備封裝:10-VSON 包裝:剪切帶 (CT) 工作溫度:-30°C ~ 85°C 產(chǎn)品目錄頁面:1371 (CN2011-ZH PDF) 其它名稱:BD1603NUV-E2CT |
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