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參數(shù)資料
| 型號： | LT3958EUHE#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, PQCC36 |
| 封裝： | 5 X 6 MM, LEAD FREE, PLASTIC, QFN-36 |
| 文件頁數(shù)： | 14/28頁 |
| 文件大小： | 320K |
| 代理商： | LT3958EUHE#PBF |
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LT3958
21
3958f
APPLICATIONS INFORMATION
Inverting Converter: Switch Duty Cycle and Frequency
For an inverting converter operating in CCM, the duty cycle
of the main switch can be calculated based on the negative
output voltage (VOUT) and the input voltage (VIN).
The maximum duty cycle (DMAX)occurswhentheconverter
has the minimum input voltage:
DMAX =
VOUT VD
VOUT VD VIN(MIN)
Inverting Converter: Output Diode and Input Capacitor
Selections
The selections of the inductor, output diode and input
capacitor of an inverting converter are similar to those
of the SEPIC converter. Please refer to the corresponding
SEPIC converter sections.
Inverting Converter: Output Capacitor Selection
The inverting converter requires much smaller output
capacitors than those of the boost, yback and SEPIC
converters for similar output ripples. This is due to the fact
that, in the inverting converter, the inductor L2 is in series
with the output, and the ripple current owing through the
output capacitors are continuous. The output ripple voltage
is produced by the ripple current of L2 owing through the
ESR and bulk capacitance of the output capacitor:
ΔVOUT(P–P) =ΔIL2 ESRCOUT +
1
8 COUT
After specifying the maximum output ripple, the user can
select the output capacitors according to the preceding
equation.
The ESR can be minimized by using high quality X5R or
X7R dielectric ceramic capacitors. In many applications,
ceramic capacitors are sufcient to limit the output volt-
age ripple.
The RMS ripple current rating of the output capacitor
needs to be greater than:
IRMS(COUT) > 0.3 ΔIL2
Inverting Converter: Selecting the DC Coupling Capacitor
The DC voltage rating of the DC coupling capacitor
(CDC, as shown in Figure 10) should be larger than the
maximum input voltage minus the output voltage (nega-
tive voltage):
VCDC > VIN(MAX) – VOUT
CDC has nearly a rectangular current waveform. During
the switch off-time, the current through CDC is IIN, while
approximately –IO ows during the on-time. The RMS
rating of the coupling capacitor is determined by the fol-
lowing equation:
IRMS(CDC) >IO(MAX)
DMAX
1DMAX
A low ESR and ESL, X5R or X7R ceramic capacitor works
well for CDC.
Board Layout
The high power and high speed operation of the LT3958
demands careful attention to board layout and component
placement. Careful attention must be paid to the internal
power dissipation of the LT3958 at high input voltages,
high switching frequencies, and high internal power switch
currents to ensure that a junction temperature of 125°C is
not exceeded. This is especially important when operating
at high ambient temperatures. Exposed pads on the bot-
tom of the package are SGND and SW terminals of the IC,
and must be soldered to a SGND ground plane and a SW
plane respectively. It is recommended that multiple vias
in the printed circuit board be used to conduct heat away
from the IC and into the copper planes with as much as
area as possible.
To prevent radiation and high frequency resonance
problems, proper layout of the components connected
to the IC is essential, especially the power paths with
higher di/dt. The following high di/dt loops of different
topologies should be kept as tight as possible to reduce
inductive ringing:
In boost conguration, the high di/dt loop contains
the output capacitor, the internal power MOSFET and
the Schottky diode.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT3958EUHETRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
| LT3958IUHE#PBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LT3958IUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LT3958IUHEPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
| LT3958IUHETRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
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