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參數資料
| 型號： | LM5027AMH |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | TSSOP-20 |
| 文件頁數： | 17/28頁 |
| 文件大?。?/td> | 561K |
| 代理商： | LM5027AMH |
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The hiccup mode provides the periodic cool-down time for the
power converter in the event of a sustained overload or short
circuit. This off time results in lower average input current and
lower power dissipation within the power components.
30111923
FIGURE 16. Hiccup Mode Timing
Printed Circuit Board Layout
The LM5027A Current Sense and PWM comparators are very
fast and respond to short duration noise pulses. The compo-
nents at the CS, COMP, SS, UVLO, TIME1, TIME2, and
TIME3 pins should be physically close as possible to the IC,
thereby minimizing noise pickup on the PC board trace in-
ductance. Layout consideration is critical for the current sense
filter. If a current sense transformer is used, both leads of the
transformer secondary should be routed to the sense filter
components and to the IC pins. The ground side of the trans-
former should be connected via a dedicated PC board trace
to the AGND pin, rather than through the ground plane.
If the current sense circuit employs a sense resistor in the
drive transistor source, low inductance resistors should be
used. In this case, all the noise sensitive, low-current ground
trace should be connected in common near the IC, and then
a single connection made to the power ground (sense resistor
ground point). The gate drive outputs of the LM5027A should
have short, direct paths to the power MOSFETs in order to
minimize inductance in the PC board. The two ground pins
(AGND, PGND) must be connected together with a short, di-
rect connection, to avoid jitter due to relative ground bounce.
Application Circuit Example
The following schematic shows an example of the LM5027A
controlling a 100W active clamp forward power converter.
The input voltage range (V
PWR) is 36V to 76V, and the output
voltage is 3.3V. The output current capability is 30 Amps.
Current sense transformer T3 provides information to the CS
pin for current limit protection. The error amplifier and refer-
ence U3 and U5 provide voltage feedback via opto-coupler
U2. Synchronous rectifiers Q3-Q6 minimize rectification loss-
es in the secondary. An auxiliary winding on the power trans-
former T1 provides power to the LM5027A VCC pin when the
output is in regulation. The input UVLO levels are 34V for in-
creasing V
PWR, and approximately 32V for decreasing VPWR.
The circuit can be shutdown by forcing the ON/OFF input J2
below 0.4V. An external synchronizing frequency can be ap-
plied to the Oscillator input. The converter output current limit
is limited at 32A.
Special care was taken in this design such that the converter
will turn on with the output pre-biased without sinking current
from the output. More information is available in TBD.
www.national.com
24
LM5027A
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LM5027AMH/NOPB | 功能描述:電壓模式 PWM 控制器 Active Clamp Pwm W/3A Sr Drv RoHS:否 制造商:Texas Instruments 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5027AMHX/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5027ASQ/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5027ASQX/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5027MH | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Voltage Mode Active Clamp Controller |
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