FSL206MRN Fairchild Semiconductor, FSL206MRN Datasheet - Page 10

• Manufacturer Part Number: FSL206MRN
• Description: Power Switch ICs - Power Distribution Low Power FPS
• Manufacturer: Fairchild Semiconductor

Specifications of FSL206MRN

• On Resistance (max): 19 Ohms
• Maximum Operating Temperature: + 115 C
• Minimum Operating Temperature: - 40 C
• Maximum Power Dissipation: 1.3 W
• Mounting Style: Through Hole
• Off Time (max): 43.6 ns
• On Time (max): 6.1 ns
• Operating Frequency: 67 KHz
• Supply Current: 0.3 mA
• Supply Voltage (min): 26 V
• Package / Case: DIP-8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

© 2010 Fairchild Semiconductor Corporation
FSL206MR • Rev. 1.0.0
Overload Protection (OLP)
Overload is defined as the load current exceeding a
pre-set level due to an unexpected event. In this
situation, the protection circuit should be activated to
protect the SMPS. However, even when the SMPS is
operating normally, the overload protection (OLP) circuit
can be activated during the load transition or startup. To
avoid this undesired operation, the OLP circuit is
activated after a specified time to determine whether it
is a transient situation or a true overload situation. The
current-mode feedback path limits the current in the
SenseFET when the maximum PWM duty cycle is
attained. If the output consumes more than this
maximum power, the output voltage (V
below its rating voltage. This reduces the current
through the opto-coupler LED, which also reduces the
opto-coupler transistor current, thus increasing the
feedback voltage (V
feedback input diode is blocked and the 2.7µA current
source (I
condition, V
switching operation is terminated, as shown in Figure
19. The shutdown delay time is the time required to
charge C
Figure 18.
Figure 19.
FB
DELAY
from 2.4V to 5V with 2.7µA current source.
FB
) starts to charge C
increases until it reaches 5V, when the
Auto-Restart Protection Waveforms
Overload Protection (OLP)
FB
). If V
FB
FB
exceeds 2.4V, the
slowly up. In this
O
) decreases
10
Abnormal Over-Current Protection (AOCP)
When the secondary rectifier diodes or the transformer
pin are shorted, a steep current with extremely high
di/dt can flow through the SenseFET during the LEB
time. Even though the FPS has overload protection, it is
not enough to protect the FPS in that abnormal case,
since severe current stress is imposed on the
SenseFET until OLP triggers. The FPS includes the
internal AOCP (Abnormal Over-Current Protection)
circuit shown in Figure 20. When the gate turn-on signal
is applied to the power sense, the AOCP block is
enabled and monitors the current through the sensing
resistor. The voltage across the resistor is compared
with a preset AOCP level. If the sensing resistor voltage
is greater than the AOCP level, the set signal is applied
to the latch, resulting in the shutdown of the SMPS.
Thermal Shutdown (TSD)
The SenseFET and the control IC are integrated,
making it easier to detect the temperature of the
SenseFET. When the junction temperature exceeds
approximately 135°C, thermal shutdown is activated
and the FPS is restarted after decreasing temperature
reaches 60°C.
Over-Voltage Protection (OVP)
In the event of a malfunction in the secondary-side
feedback circuit or an open feedback loop caused by a
soldering defect, the current through the opto-coupler
transistor becomes almost zero (refer to Figure 17).
Then, V
situation, forcing the preset maximum current to be
supplied to the SMPS until the overload protection is
activated. Because excess energy is provided to the
output, the output voltage may exceed the rated voltage
before the overload protection is activated, resulting in
the breakdown of the devices in the secondary side. To
prevent this situation, an over-voltage protection (OVP)
circuit is employed. In general, V
output voltage and the FPS uses V
monitoring the output voltage. If V
OVP circuit is activated, resulting in termination of the
switching operation. To avoid undesired activation of
OVP during normal operation, V
designed to be below 24.5V.
Figure 20.
FB
climbs up in a similar manner to the overload
Abnormal Over-Current Protection
CC
CC
is proportional to the
CC
CC
should be properly
instead of directly
exceeds 24.5V,
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