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| 型号： | 750108 |
| 厂商： | Wurth Electronics Inc |
| 文件页数： | 23/30页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR LT3748 |
| 设计资源： | LT3748 Design Schematic/Tips |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，隔离 |
| 功率 - 输出： | 30W |
| 输出电压： | 12V |
| 电流 - 输出： | 2.5A |
| 输入电压： | 22 ~ 75 V |
| 稳压器拓扑结构： | 回扫 |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | LT3748 |
| 相关产品： | LT3748HMS#TRPBF-ND - IC REG CTRLR FLYBK ISO CM 16MSOP LT3748HMS#PBF-ND - IC REG CTRLR FLYBK ISO CM 16MSOP LT3748IMS#TRPBF-ND - IC REG CTRLR FLYBK ISO CM 16MSOP LT3748IMS#PBF-ND - IC REG CTRLR FLYBK ISO CM 16MSOP LT3748EMS#TRPBF-ND - IC REG CTRLR FLYBK ISO CM 16MSOP LT3748EMS#PBF-ND - IC REG CTRLR FLYBK ISO CM 16MSOP |
| 其它名称： | 732-3308 |
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LT3748
APPLICATIONS INFORMATION
DESIGN EXAMPLE: 48V IN 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 V OUT 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 R DS(ON) is of minimum benefit. However, since
the current for the gate drive is pulled from a high V IN ,
minimizing both Q G and operating frequency is essential
unless a third winding is added. The Vishay Si7464DP, with
a 200V V DS(MAX) and low gate charge, keeps the INTV CC
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 R REF and R FB 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 V IN 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 INTV CC 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.
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 V IN .
Table 3. Voltage Stresses, Output Capability and Diode Current vs Turns Ratio in 48V IN to 12V, 2A Application
N PS
1
2
4
6
V DS(MAX)
84
96
120
144
V R(DIODE)
84
48
30
24
D (V IN = 48V)
0.21
0.34
0.51
0.61
D (V IN = 36V)
0.26
0.41
0.58
0.68
I LIM (2A OUT AT V IN = 36V)
6
4
3
2
I DIODE(RMS) (V IN = 48V)
3.3
3.7
4.6
5.2
3748fa
23
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 750109 | 制造商:Pilz International 功能描述:CONTACT MODULE 3NO/1NC 24V 制造商:PILZ 功能描述:CONTACT MODULE, 3NO/1NC, 24V, 30OHM 制造商:PILZ 功能描述:CONTACT MODULE, 3NO/1NC, 24V, 30OHM; Coil Voltage VDC Nom:24V; Contact Current Max:6A; Contact Voltage AC Nom:240V; Contact Voltage DC Max:24V; Coil Resistance:30ohm; Contact Configuration:3PST-NO, SPST-NC; Average Power ;RoHS Compliant: Yes |
| 750-109 | 功能描述:安装硬件 CIRC-O-GIDE .75in Nylon Black 94V-0 RoHS:否 制造商:Harwin 类型:SMT Cable Clip 材料:Phosphor Bronze 安装孔大小: 长度:5 mm 外径: 内径: 厚度: 电镀:Tin 螺纹大小: |
| 75010BK002 | 制造商:Alpha Wire Company 功能描述:Cat5e cable 2 pair solid 105deg 152m |
| 75010-BK002 | 制造商:Alpha Wire 功能描述: |
| 75-010BP | 制造商:RAYHOME 功能描述:ST/STEEL SHIM 0.10X75X75 |
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