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| 型号： | LT3748EMS#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/30页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO CM 16MSOP |
| 产品培训模块： | LT3748 100V Flyback Controller |
| 特色产品： | LT3748 Isolated Flyback Controller |
| 标准包装： | 37 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 电源电压： | 5 V ~ 100 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-TFSOP（0.118"，3.00mm），12 引线 |
| 包装： | 管件 |
| 配用： | 732-3308-ND - BOARD EVAL FOR LT3748 732-3305-ND - BOARD EVAL FOR LT3748 |
| 相关产品： | 732-2669-2-ND - TRANS FLYBACK LT3748 20UH SMD 732-2669-6-ND - TRANS FLYBACK LT3748 20UH SMD 732-2668-6-ND - TRANS FLYBACK LT3748 14UH SMD 732-2667-6-ND - TRANS FLYBACK LT3748 500UH SMD 732-2666-6-ND - TRANS FLYBACK LT3748 12UH SMD 732-2665-6-ND - TRANS FLYBACK LT3748 12UH SMD 732-2664-6-ND - TRANS FLYBACK LT3748 15UH SMD 732-2663-6-ND - TRANS FLYBACK LT3748 15UH SMD 732-2662-6-ND - TRANS FLYBACK LT3748 8UH SMD 732-2661-6-ND - TRANS FLYBACK LT3748 8UH SMD 更多... |
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LT3748
APPLICATIONS INFORMATION
The current limitation on output power delivery is gen-
erally constrained by transformer saturation current in
higher power applications, although the MOSFET switch
and output diode will need to be rated for the desired
currents, as well. Increasing the peak current on the pri-
mary side of the flyback by reducing the R SENSE resistor
is the primary way to increase output power, and power
delivered increases fairly linearly with current limit as
shown in Figure 2, until parasitic losses begin to dominate.
However, once the saturation current of the transformer
is exceeded the energy coupling between the primary and
the secondary will be reduced and incremental power will
not be delivered to the output. In addition, the primary
inductance will drop, the SENSE pin overcurrent threshold
may trip due to a corresponding rapid rise in current, and
the transformer will have to absorb the energy that is not
transferred through the saturated core, leading to heating.
Some manufacturers may not specify the rated saturation
current but it is a necessary specification when trying to
minimize transformer size and maximize output power
and efficiency. Also necessary for proper design is data
on saturation current over temperature—the saturation
of typical power ferrites may reduce by over 20% from
25°C to 100°C.
The thermal limitation in flyback applications for lower
output voltages will be dominated by losses in the output
diode, with resistive and leakage losses in the transformer
50
I LIM = 3A
40
I LIM = 2A
30
increasing as a percentage basis of loss as the output
voltage is increased. As power levels increase the output
diode and transformer may exceed their rated temperature
specifications. Minimizing RMS output diode current,
selecting a diode with minimal forward drop at expected
currents and minimizing parasitic resistances and leakage
inductance in the transformer will keep those components
below their maximum temperatures while maximizing
efficiency. The following section discussing transformer
selection will further help focus on how to minimize losses
in the output diode.
While quiescent current in the LT3748 itself is low (ap-
proximately 300μA from V IN and 1mA from INTV CC ), the
current required to drive the external MOSFET (f SW ? Q G ), if
drawn from V IN through the LT3748 INTV CC LDO, dissipates
(V IN – INTV CC ) ? f SW ? Q G . If that power is high enough to
cause significant heating of the LT3748 the current may
need to be drawn from a third winding. Doing so will push
all thermal limitations outside of the LT3748.
Selecting a Transformer
Transformer specification and design is perhaps the most
critical part of successfully applying the LT3748. In addition
to the usual list of caveats dealing with high frequency
isolated power supply transformer design, the following
information should be carefully considered.
First and most importantly, since the voltage on the sec-
ondary side of the transformer is inferred by the voltage
sampled on the primary, the transformer turns ratio must
be tightly controlled to ensure a consistent output volt-
age. A tolerance of ±5% in turns ratio from transformer to
transformer could result in a variation of more than ±5% in
output regulation. Fortunately, most magnetic component
20
10
I LIM = 1A
manufacturers are capable of guaranteeing a turns ratio
tolerance of 1% or better.
Linear Technology has worked with several leading mag-
0
0
20
40 60
INPUT VOLTAGE (V)
80
100
netic component manufacturers to produce predesigned
flyback transformers for use with the LT3748. Table 1
3748 F02
shows the details of several of these transformers.
Figure 2. Maximum Output Power at 12V OUT
with 150V V DS(MAX) and I LIM = 1A, 2A, 3A
3748fa
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3748EMSTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller |
| LT3748HMS#PBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LT3748HMS#TRPBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT3748HMSPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller |
| LT3748HMSTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller |
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