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参数资料
| 型号： | LT3574EMS#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/24页 |
| 文件大小： | 0K |
| 描述： | IC REG FLYBK ISO ADJ .65A 16MSOP |
| 标准包装： | 2,500 |
| 类型： | 回扫，隔离 |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 60V |
| 输入电压： | 3 V ~ 40 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 40kHz ~ 1MHz |
| 电流 - 输出： | 650mA |
| 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： | 16-TFSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-MSOP |
| 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... |
LT3574
APPLICATIONS INFORMATION
BIAS winding turns ratio is selected to program the BIAS
voltage to 3~5V. The BIAS voltage shall not exceed the
input voltage.
The turns ratio is then selected as primary: secondary:
BIAS = 3:1:1.
2. Select the transformer primary inductance for target
switching frequency.
The LT3574 requires a minimum amount of time to sample
the output voltage during the off-time. This off-time,
t OFF(MIN) , shall be greater than 350ns over all operating
conditions. The converter also has a minimum current limit,
I MIN , of 175mA to help create this off-time. This defines
the minimum required inductance as defined as:
In this design example, the minimum primary inductance is
used to achieve a nominal switching frequency of 350kHz
at full load. The PA2627NL from Pulse Engineering is
chosen as the flyback transformer.
Given the turns ratio and primary inductance, a custom-
ized transformer can be designed by magnetic component
manufacturer or a multi-winding transformer such as a
Coiltronics Versa-Pac may be used.
3. Select the output diodes and output capacitor.
The output diode voltage stress V D is the summation of
the output voltage and reflection of input voltage to the
secondary side. The average diode current is the load
current.
L MIN =
N( V OUT + V F )
I MIN
? t OFF ( MIN )
V D = V OUT +
V IN
N
f SW =
=
t ON + t OFF I PK I PK
+ V
V IN
N PS OUT F )
+
LI 2 PK
D V MAX =
The transformer primary inductance also affects the
switching frequency which is related to the output ripple. If
above the minimum inductance, the transformer’s primary
inductance may be selected for a target switching frequency
range in order to minimize the output ripple.
The following equation estimates the switching frequency.
1 1
( V
L L
Table 7. Switching Frequency at Different Primary Inductance
at I PK
f SW AT V IN(MIN) f SW AT V IN(MAX)
L (μH) (kHz) (kHz)
30 317 373
60 159 187
The output capacitor should be chosen to minimize the
output voltage ripple while considering the increase in
size and cost of a larger capacitor. The following equation
calculates the output voltage ripple.
2 CV OUT
4. Select the snubber circuit to clamp the switch voltage
spike.
A flyback converter generates a voltage spike during switch
turn-off due to the leakage inductance of the transformer.
In order to clamp the voltage spike below the maximum
rating of the switch, a snubber circuit is used. There are
many types of snubber circuits, for example R-C, R-C-D and
Zener clamps. Among them, RCD is widely used. Figure 9
shows the RCD snubber in a flyback converter.
120
79
93
A typical switch node waveform is shown in Figure 10.
Note: The switching frequency is calculated at maximum output.
3574f
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3574IMS | 制造商:LINER 制造商全称:Linear Technology 功能描述:Isolated Flyback Converter Without an Opto-Coupler |
| LT3574IMS#PBF | 功能描述:IC REG FLYBK ISO ADJ .65A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3574IMS#TRPBF | 功能描述:IC REG FLYBK ISO ADJ .65A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3574IMSPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Isolated Flyback Converter Without an Opto-Coupler |
| LT3574IMSTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Isolated Flyback Converter Without an Opto-Coupler |
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