FSL137H Fairchild Semiconductor, FSL137H Datasheet - Page 11

• Manufacturer Part Number: FSL137H
• Description: The highly integrated FSL137H consists of an integrated current mode Pulse Width Modulator (PWM) and an avalanche-rugged 700V SenseFET
• Manufacturer: Fairchild Semiconductor

© 2009 Fairchild Semiconductor Corporation
FSL137H Rev. 1.0.3
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
high/low line compensation function generates a
relative peak-current-limit threshold voltage for constant
power control, as shown in Figure 27.
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 V
latched until the V
recovery when V
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.
Figure 27.
Figure 28.
IN
DD
is lower than 0.3V.
IN
is discharged. FSL137H is in auto
Constant Power Control
is higher than 5.2V, FSL137H is
VIN Pin Function
11
V
V
by over voltage on the V
when V
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.
approximately 142°C, thermal shutdown is activated.
DD
DD
Vo
Over-Voltage Protection (OVP)
over-voltage protection prevents IC damage caused
Feedback Open
DD
reaches 28V. It has a debounce time (typically
Loop
Figure 29.
When
KA431
V
FB
the
DD
OLP Operation
pin. The OVP is triggered
temperature
4.6V
6V
3R
R
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56ms
PWM
exceeds
OLP