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参数资料
| 型号： | LT3573EMSE#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1.85 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 8/26页 |
| 文件大小： | 1182K |
| 代理商： | LT3573EMSE#TRPBF |
LT3573
3573fc
applications inForMation
The transformer turns ratio is selected such that the con-
verter has adequate current capability and a switch stress
below 50V. Table 6 shows the switch voltage stress and
output current capability at different transformer turns
ratio.
Table 6. Switch Voltage Stress and Output Current Capability vs
Turns-Ratio
N
VSW(MAX) AT VIN(MAX)
(V)
IOUT(MAX) AT VIN(MIN)
(A)
DUTY CYCLE
(%)
1:1
33.5
0.53
16~22
2:1
39
0.88
28~35
3:1
44.5
1.12
37~45
4:1
50
1.30
44~52
BIAS winding turns ratio is selected to program the BIAS
voltage to 3V~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 LT3573 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,
LMIN, of 250mA 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.
The following equation estimates the switching frequency.
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)
25
236
305
50
121
157
100
61
80
Note: The switching frequency is calculated at maximum output.
Inthisdesignexample,theminimumprimaryinductanceis
used to achieve a nominal switching frequency of 275kHz
at full load. The PA2454NL 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
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3573IMSE#PBF | 功能描述:IC REG FLYBACK ISO ADJ 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:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 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:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT3573IMSE#PBF | 制造商:Linear Technology 功能描述:DC-DC CONVERTER FLYBACK 1MHZ MSOP-16 制造商:Linear Technology 功能描述:DC-DC CONVERTER, FLYBACK, 1MHZ, MSOP-16 |
| LT3573IMSE#TRPBF | 功能描述:IC REG FLYBACK ISO ADJ 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 |
| LT3573IMSEPBF | 制造商:Linear Technology 功能描述:Isolated Flyback Converter, No-Opto MSOP |
| LT3573IMSE-PBF | 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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