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FSL117MRIN 参数 Datasheet PDF下载

FSL117MRIN图片预览
型号: FSL117MRIN
PDF下载: 下载PDF文件 查看货源
内容描述: 绿色模式飞兆功率开关( FPSA ?? ¢ ) [Green-Mode Fairchild Power Switch (FPS™)]
分类和应用: 开关
文件页数/大小: 15 页 / 1556 K
品牌: FAIRCHILD [ FAIRCHILD SEMICONDUCTOR ]
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4.3. Output-Short Protection (OSP): If the output is  
shorted, steep current with extremely high di/dt can  
flow through the SenseFET during the minimum turn-  
on time. Such a steep current creates high-voltage  
stress on the drain of the SenseFET when turned off.  
To protect the device from this abnormal condition,  
OSP is included. It is comprised of detecting VFB and  
SenseFET turn-on time. When the VFB is higher than  
2.0V and the SenseFET turn-on time is lower than  
1.0μs, the FSL117MRIN recognizes this condition as  
an abnormal error and shuts down PWM switching  
until VCC reaches VSTART again. An abnormal condition  
output short is shown in Figure 23.  
4.6 Line Over-Voltage Protection (LOVP): If the line  
input voltage is increased until unwanted level, high  
line input voltage brings high-voltage stress on the  
entire system. To protect from this abnormal  
condition, LOVP is included. It is comprised of  
detecting VIN using divided resistors. When VIN is  
higher than 1.95V, this condition is recognized as an  
abnormal error and PWM switching shuts down until  
VIN decreases to around 1.89V (60mV hysteresis).  
Figure 24. Line Over-Voltage Protection  
5. Soft Burst Mode: To minimize power dissipation in  
Standby Mode, the FSL117MRIN enters Burst Mode.  
As the load decreases, the feedback voltage  
decreases. The device automatically enters Burst  
Mode when the feedback voltage drops below VBURL  
(300mV), as shown in Figure 25. At this point,  
switching stops and the output voltages start to drop  
at a rate dependent on standby current load. This  
causes the feedback voltage to rise. Once it passes  
VBURH (450mV), switching resumes. Feedback voltage  
then falls and the process repeats. Burst Mode  
alternately enables and disables switching of the  
SenseFET, reducing switching loss in Standby Mode.  
Figure 23. Output-Short Protection  
4.4 Over-Voltage Protection (OVP): If the  
secondary-side feedback circuit malfunctions or a  
solder defect causes an opening in the feedback path,  
the current through the opto-coupler transistor  
becomes almost zero. Then VFB climbs up in a similar  
manner to the overload situation, forcing the preset  
maximum current to be supplied to the SMPS until the  
overload protection is triggered. Because more  
energy than required is provided to the output, the  
output voltage may exceed the rated voltage before  
the overload protection is triggered, resulting in the  
breakdown of the devices in the secondary side. To  
prevent this situation, an OVP circuit is employed. In  
general, the VCC is proportional to the output voltage  
and the FSL117MRIN uses VCC instead of directly  
monitoring the output voltage. If VCC exceeds 24.5V,  
an OVP circuit is triggered, resulting in the termination  
of the switching operation. To avoid undesired  
activation of OVP during normal operation, VCC should  
be designed to be below 24.5V.  
4.5 Thermal Shutdown (TSD): The SenseFET and  
the control IC on a die in one package makes it easier  
for the control IC to detect the temperature of the  
SenseFET. If the temperature exceeds ~140C, the  
thermal shutdown is triggered and stops operation.  
The FSL117MRIN operates in auto-restart mode until  
the temperature decreases to around 75C, when  
normal operation resumes.  
Figure 25. Burst-Mode Operation  
© 2012 Fairchild Semiconductor Corporation  
FSL117MRN • Rev.1.0.0  
www.fairchildsemi.com  
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