FSL137H データシートの表示（PDF） - Fairchild Semiconductor
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FSL137H Datasheet PDF : 15 Pages
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Constant Power Control
To limit the output power of the converter constantly,
high/low line compensation is included. Sensing the
converter input voltage through the VIN pin, the
Vo
high/low line compensation function generates a
relative peak-current-limit threshold voltage for constant
power control, as shown in Figure 27.
VFB
KA431
Feedback Open
Loop
6V
PWM
3R
R
4.6V
56ms OLP
Figure 27. Constant Power Control
Protections
The FSL137H provides full protection functions to
prevent the power supply and the load from being
damaged. The protection features include:
Latch / Auto Recovery Function
The FSL137H provides additional protections by the
VIN pin, such as pull-HIGH latch and pull-LOW auto
recovery that depend on the application. As shown in
Figure 28, when VIN is higher than 5.2V, FSL137H is
latched until the VDD is discharged. FSL137H is in auto
recovery when VIN is lower than 0.3V.
Figure 29. OLP Operation
VDD Over-Voltage Protection (OVP)
VDD over-voltage protection prevents IC damage caused
by over voltage on the VDD pin. The OVP is triggered
when VDD reaches 28V. It has a debounce time (typically
130µs) to prevent false trigger by switching noise.
Over-Temperature Protection (OTP)
The SenseFET and the control IC are integrated,
making it easier to detect the temperature of the
SenseFET. When the temperature exceeds
approximately 142°C, thermal shutdown is activated.
Figure 28. VIN Pin Function
Open-Loop / Overload Protection (OLP)
When the upper branch of the voltage divider for the
shunt regulator (KA431 shown) is broken, as shown in
Figure 29, or over current or output short occurs. There
is no current flowing through the opto-coupler transistor,
which pulls up the feedback voltage to 6V. When the
feedback voltage is above 4.6V for longer than 56ms,
OLP is triggered. This protection is also triggered when
the SMPS output drops below the nominal value longer
than 56ms due to the overload condition.
© 2009 Fairchild Semiconductor Corporation
FSL137H Rev. 1.0.3
11
www.fairchildsemi.com
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