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參數(shù)資料
| 型號： | LT3758HMSE#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | 3 X 3 MM, LEAD FREE, PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 9/36頁 |
| 文件大小： | 554K |
| 代理商： | LT3758HMSE#PBF |
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LT3758
17
3758fc
ApplicAtions inForMAtion
Figure 6. The Output Ripple Waveform of a Boost Converter
VOUT
(AC)
tON
VESR
RINGING DUE TO
TOTAL INDUCTANCE
(BOARD + CAP)
VCOUT
3758 F06
tOFF
The output capacitor in a boost regulator experiences high
RMS ripple currents, as shown in Figure 6. The RMS ripple
current rating of the output capacitor can be determined
using the following equation:
IRMS(COUT) ≥IO(MAX)
DMAX
1
DMAX
Multiple capacitors are often paralleled to meet ESR
requirements. Typically, once the ESR requirement is
satisfied, the capacitance is adequate for filtering and has
therequiredRMScurrentrating.Additionalceramiccapaci-
tors in parallel are commonly used to reduce the effect of
parasiticinductanceintheoutputcapacitor,whichreduces
high frequency switching noise on the converter output.
Boost Converter: Input Capacitor Selection
The input capacitor of a boost converter is less critical
than the output capacitor, due to the fact that the inductor
is in series with the input, and the input current wave-
form is continuous. The input voltage source impedance
determines the size of the input capacitor, which is typi-
cally in the range of 10F to 100F. A low ESR capacitor
is recommended, although it is not as critical as for the
output capacitor.
The RMS input capacitor ripple current for a boost con-
verter is:
IRMS(CIN) = 0.3 IL
FLYBACK CONVERTER APPLICATIONS
TheLT3758canbeconfiguredasaflybackconverterforthe
applications where the converters have multiple outputs,
high output voltages or isolated outputs. Figure 7 shows
a simplified flyback converter.
The flyback converter has a very low parts count for mul-
tiple outputs, and with prudent selection of turns ratio, can
have high output/input voltage conversion ratios with a
desirable duty cycle. However, it has low efficiency due to
thehighpeakcurrents,highpeakvoltagesandconsequent
power loss. The flyback converter is commonly used for
an output power of less than 50W.
The RθJA to be used in this equation normally includes the
RθJC for the device plus the thermal resistance from the
board to the ambient temperature in the enclosure. TJ must
notexceedthediodemaximumjunctiontemperaturerating.
Boost Converter: Output Capacitor Selection
Contributions of ESR (equivalent series resistance), ESL
(equivalent series inductance) and the bulk capacitance
must be considered when choosing the correct output
capacitors for a given output ripple voltage. The effect of
thesethreeparameters(ESR,ESLandbulkC)ontheoutput
voltage ripple waveform for a typical boost converter is
illustrated in Figure 6.
The choice of component(s) begins with the maximum
acceptable ripple voltage (expressed as a percentage of
the output voltage), and how this ripple should be divided
between the ESR step VESR and the charging/discharg-
ing VCOUT. For the purpose of simplicity, we will choose
2% for the maximum output ripple, to be divided equally
between VESR and VCOUT. This percentage ripple will
change, depending on the requirements of the applica-
tion, and the following equations can easily be modified.
For a 1% contribution to the total ripple voltage, the ESR
of the output capacitor can be determined using the fol-
lowing equation:
ESRCOUT ≤
0.01 VOUT
ID(PEAK)
For the bulk C component, which also contributes 1% to
the total ripple:
COUT ≥
IO(MAX)
0.01 VOUT f
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| LT3758IDD#PBF | 功能描述:IC REG CTRLR BST FLYBK INV 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LT3758IDD#TRPBF | 功能描述:IC REG CTRLR BST FLYBK INV 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LT3758IDDPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Controller |
| LT3758IDDTRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Controller |
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