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参数资料
| 型号： | LT3958EUHE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 17/28页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ 36VQFN |
| 特色产品： | LT?3957/LT?3958 Converters |
| 标准包装： | 61 |
| 类型： | 升压（升压），反相，回扫，Sepic |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.6 V ~ 80 V |
| 输入电压： | 5 V ~ 80 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz ~ 1MHz |
| 电流 - 输出： | 3.3A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 36-QFN-EP（6x5） |
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LT3958
APPLICATIONS INFORMATION
According to the preceding equations, the user has relative
freedom in selecting the switch duty cycle or turns ratio to
suit a given application. The selections of the duty cycle
and the turns ratio are somewhat iterative processes, due
to the number of variables involved. The user can choose
either a duty cycle or a turns ratio as the start point. The
following trade-offs should be considered when select-
ing the switch duty cycle or turns ratio, to optimize the
converter performance. A higher duty cycle affects the
?yback converter in the following aspects:
? Lower MOSFET RMS current I SW(RMS) , but higher
MOSFET V SW peak voltage
? Lower diode peak reverse voltage, but higher diode
output current capability. Choosing smaller values of Δ I SW
increases the output current capability, but requires large
primary and secondary inductances and reduce the cur-
rent loop gain (the converter will approach voltage mode).
Accepting larger values of Δ I SW allows the use of low
primary and secondary inductances, but results in higher
input current ripple, greater core losses, and reduces the
output current capability. It is recommended to choose a
Δ I SW higher than 0.6A.
Given an operating input voltage range, and having chosen
the operating frequency and ripple current in the primary
winding, the primary winding inductance can be calculated
using the following equation:
RMS current I D(RMS)
? Higher transformer turns ratio (N P /N S )
L =
V IN(MIN)
Δ I SW ? ?
? D MAX
It is recommended to choose a duty cycle between 20%
and 80%.
Flyback Converter: Maximum Output Current
The primary winding peak current is the switch current
limit (typical 4A). The primary and secondary maximum
RMS currents are:
Capability and Transformer Design
The maximum output current capability and transformer
design for continuous conduction mode (CCM) is chosen
as presented here.
The maximum duty cycle (D MAX ) occurs when the converter
I LP(RMS) ≈
I LS(RMS) ≈
P OUT(MAX)
D MAX ? V IN(MIN) ? η
I OUT(MAX)
1 ? D MAX
has the minimum V IN :
where η is the converter ef?ciency.
V OUT ? ? P ?
V OUT ? ? P ? + V IN(MIN)
D MAX =
? N ?
?N S ?
? N ?
? N S ?
Based on the preceding equations, the user should de-
sign/choose the transformer having suf?cient saturation
and RMS current ratings.
Flyback Converter: Snubber Design
? D MAX ? ( 3.3A ? 0.5 ? Δ I SW )
I O(MAX) ≤
Due to the current limit of its internal power switch, the
LT3958 should be used in a ?yback converter whose maxi-
mum output current (I O(MAX) ) is less than the maximum
output current capability by a suf?cient margin (10% or
higher is recommended):
V IN(MIN)
V OUT
The transformer ripple current Δ I SW has a direct effect on
Transformer leakage inductance (on either the primary
or secondary) causes a voltage spike to occur after the
MOSFET turn-off. This is increasingly prominent at higher
load currents, where more stored energy must be dis-
sipated. In some cases a snubber circuit will be required
to avoid overvoltage breakdown at the MOSFET’s drain
node. There are different snubber circuits (such as RC
snubber, RCD snubber, etc.) and Application Note 19 is
a good reference on snubber design. An RCD snubber is
shown in Figure 6.
the design/choice of the transformer and the converter’s
3958f
17
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3958EUHETRPBF | 制造商:LINER 制造商全称: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 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3958IUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3958IUHEPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
| LT3958IUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
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