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參數資料
| 型號： | FAN5231QSC |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩壓器 |
| 英文描述： | Analog IC |
| 中文描述： | 0.34 A SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | PLASTIC, QSOP-28 |
| 文件頁數： | 14/17頁 |
| 文件大小： | 360K |
| 代理商： | FAN5231QSC |
FAN5231
14
REV. 1.1.1 8/15/01
MOSFET Selection and Considerations
Requirements for upper and lower MOSFETs are different
in mobile applications. The reason for this is the 10:1 differ-
ence in conduction time of the lower and the upper MOS-
FETs driven by a difference between the input voltage which
is nominally in the range from 8V to 20V and output voltage
which is about 1.5V.
Requirements for the lower MOSFET are simpler than those
for the upper one. The lower the Rdson of this device the
lower the conduction losses, and the higher converter’s
efficiency. Switching losses and gate drive losses are not
significant because of zero-voltage switching conditions
inherent for this device in the buck converter. Important is
low reverse recovery charge of the body diode which causes
shoot-trough current spikes when the upper MOSFET turns
on. Also, important is to verify that the lower MOSFET gate
voltage does not reach threshold when high dV/dt transition
occurs on the phase node. Specially for that reason,
FAN5231 is equipped with a low, 1.0
typical, pull-down
resistance of low side driver.
Requirements for the upper MOSFET Rdson are less
stringent than for the lower MOSFET because its conduction
time is significantly shorter while switching losses can
dominate especially at higher input voltages. It is recom-
mended to have equal conduction and switching losses in the
upper MOSFET at the nominal input voltage and load
current. In this case maximum converter efficiency is tuned
to the operation point that it is most desired.
Precise calculation of power dissipation in the MOSFETs is
very complex because many parameters affecting turn-on
and turn-off times such as gate reverse transfer charge, gate
internal resistance, body diode reverse recovery charge,
package and layout impedances and their variation with the
operation conditions are not available to a designer. Follow-
ing equations are provided only for crude estimation of the
power losses and should be accompanied by a detail bread-
board evaluation. Attention should be paid to the input
voltage extremes where power dissipation in the MOSFETs
is usually higher.
Plower
Io
2
Rdson
1
V
in
----out
–
×
×
=
Pupper
2
-o
Rdson
V
in
Vout
×
×
-o
Vin
Fs
ton
toff
+
(
)
×
×
×
2
+
=
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相關代理商/技術參數 |
參數描述 |
|---|---|
| FAN5231QSCX | 功能描述:開關變換器、穩壓器與控制器 QSOP-28 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| FAN5232 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Adjustable PWM Buck Controller for LCD PCs |
| FAN5232_CBC3116B WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| FAN5232MTC | 功能描述:DC/DC 開關控制器 DC/DC RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| FAN5232MTC_NL | 功能描述:開關變換器、穩壓器與控制器 ANG FG RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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