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參數資料
| 型號： | LT3748HMS#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO12 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-16/12 |
| 文件頁數： | 16/30頁 |
| 文件大?。?/td> | 284K |
| 代理商： | LT3748HMS#PBF |
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LT3748
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3748fa
APPLICATIONS INFORMATION
Table 3. Voltage Stresses, Output Capability and Diode Current vs Turns Ratio in 48VIN to 12V, 2A Application
NPS
VDS(MAX)
VR(DIODE)
D (VIN = 48V)
D (VIN = 36V)
ILIM (2A OUT AT VIN = 36V)
IDIODE(RMS) (VIN = 48V)
1
84
0.21
0.26
6
3.3
2
96
48
0.34
0.41
4
3.7
4
120
30
0.51
0.58
3
4.6
6
144
24
0.61
0.68
2
5.2
DESIGN EXAMPLE: 48VIN TO 12V, 2A OUT
The second example is a telecom application shown on the
front page of the datasheet. The focus of this application
is a cheap, small and simple solution. Table 3 shows the
results of the initial step for selecting the turns ratio.
In this example, the output diode is a much smaller ef-
ficiency loss due to the smaller voltage drop across it in
ratio to VOUT so minimizing output diode current is not
as important. Of greater importance is minimizing the
stresses on the MOSFET and output diode and the 4:1
case seems to be the best compromise for that to avoid
using a snubber on either device.
20μH of primary inductance is required for minimum
off-time while selecting the transformer, but in order to
minimize output ripple at maximum load a 60.8μH trans-
former is selected. To meet the saturation current (12A,
peak, on the secondary windings), a Versa-Pak VP4-0047-R
provides a compact and efficient solution.
For the MOSFET switch, since the input voltage is so high,
resistive losses on the primary side will be very low so
minimizing RDS(ON) is of minimum benefit. However, since
the current for the gate drive is pulled from a high VIN,
minimizing both QG and operating frequency is essential
unless a third winding is added. The Vishay Si7464DP, with
a 200V VDS(MAX) and low gate charge, keeps the INTVCC
current to just over 3mA, worst-case, which when added
to quiescent current will keep power dissipation in the
LT3748 to just over 1/4W at 72V VIN.
The output diode only nominally has 30V of reverse bias
but a B360 diode is selected to ensure enough margin that
a snubber will not be required. A more expensive diode
with lower forward drop might recover several percent
efficiency and if high temperature operation is required a
diode rated for more average current at temperature might
be needed, but the B360 is small and inexpensive.
The rest of the design and component selection is straight-
forward.
Suggested Layout
See Figures 13 and 14 for the DC1557A demo board layout.
Note the proximity of the RREF and RFB resistors (R9, R5)
to the LT3748 for optimal regulation. The location of these
two resistors as close to the physical pins of the LT3748
is critical for accurate regulation. In addition, the high
frequency current path from the VIN bypass capacitor (C2)
through the primary-side winding, the MOSFET switch and
sense resistor (R10) is a very tight loop. Similarly, the high
frequency current path for the MOSFET gate switching from
the INTVCC capacitor through the source of the MOSFET
and sense resistor is similarly small in area. For improved
regulation it is recommended that the user ensure that the
high current ground is kept separate or at least physically
isolated from the small-signal ground used by the other
ground-referenced pins.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LT3748HMSTRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:100V Isolated Flyback Controller |
| LT3748IMS#PBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數: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) |
| LT3748IMS#TRPBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數: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) |
| LT3748IMSPBF | 制造商:Linear Technology 功能描述:100V Isolated Flyback Controller MSOP16 |
| LT3748IMSTRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:100V Isolated Flyback Controller |
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