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参数资料
| 型号： | LT3574EMS#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1.1 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 8/24页 |
| 文件大小： | 285K |
| 代理商： | LT3574EMS#TRPBF |
LT3574
3574f
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,
tOFF(MIN), shall be greater than 350ns over all operating
conditions.Theconverteralsohasaminimumcurrentlimit,
IMIN, of 175mA to help create this off-time. This defines
the minimum required inductance as defined as:
L
N V
V
I
t
MIN
OUT
F
MIN
OFF MIN
=
+
(
)
(
)
The transformer primary inductance also affects the
switching frequency which is related to the output ripple. If
abovetheminimuminductance,thetransformer’sprimary
inductancemaybeselectedforatargetswitchingfrequency
range in order to minimize the output ripple.
Thefollowingequationestimatestheswitchingfrequency.
f
t
I
V
L
I
N
V
L
SW
ON
OFF
PK
IN
PK
PS OUT
F
=
+
=
+
1
(
)
Table 7. Switching Frequency at Different Primary Inductance
at IPK
L (H)
fSW AT VIN(MIN)
(kHz)
fSW AT VIN(MAX)
(kHz)
30
317
373
60
159
187
120
79
93
Note: The switching frequency is calculated at maximum output.
Inthisdesignexample,theminimumprimaryinductanceis
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 VD is the summation of
the output voltage and reflection of input voltage to the
secondary side. The average diode current is the load
current.
V
N
D
OUT
IN
=
+
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.
DV
LI
CV
MAX
PK
OUT
=
2
4. Select the snubber circuit to clamp the switch voltage
spike.
Aflybackconvertergeneratesavoltagespikeduringswitch
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
manytypesofsnubbercircuits,forexampleR-C,R-C-Dand
Zener clamps. Among them, RCD is widely used. Figure 9
shows the RCD snubber in a flyback converter.
A typical switch node waveform is shown in Figure 10.
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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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