FSQ211L Fairchild Semiconductor, FSQ211L Datasheet - Page 9

• Manufacturer Part Number: FSQ211L
• Description: IC SWIT PWM GREEN UVLO HV 8SOP
• Manufacturer: Fairchild Semiconductor

Specifications of FSQ211L

• Output Isolation: Isolated
• Frequency Range: 61 ~ 73kHz
• Voltage - Input: 8 ~ 20 V
• Voltage - Output: 650V
• Power (watts): 1.4W
• Operating Temperature: 25°C ~ 145°C
• Package / Case: 8-SOP, 8-LSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

© 2007 Fairchild Semiconductor Corporation
FSQ211 Rev. 1.0.0
4.1 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 over-
load protection (OLP) circuit can be activated during the
load transition. To avoid this undesired operation, the
OLP circuit is designed to be activated after a specified
time to determine whether it is a transient situation or an
overload situation. If the output consumes more than the
maximum power determined by I
(V
the current through the opto-coupler LED, which also
reduces the opto-coupler transistor current, thus
increasing the feedback voltage (V
3V, the feedback input diode is blocked and the 5µA
current source (I
V
4.5V, when the switching operation is terminated, as
shown in Figure 18. Shutdown delay is the time required
to charge C
4.2 Thermal Shutdown (TSD): The SenseFET and the
control IC are integrated, making it easier for the control
IC to detect the temperature of the SenseFET. When
the temperature exceeds approximately 145°C, thermal
shutdown is activated.
5. Soft-Start: The FPS has an internal soft-start circuit
that slowly increases the feedback voltage, together with
the SenseFET current, right after it starts up. The typical
soft-start time is 15ms, as shown in Figure 19, where
progressive increment of the SenseFET current is
allowed during the start-up phase. Soft-start circuit
progressively increases current limits to establish proper
working
capacitors, and switching device. It also helps prevent
transformer saturation and reduces the stress on the
secondary diode.
4.5V
CC
V
3V
O
t
FB
1 2
) decreases below its rating voltage. This reduces
. In this condition, V
=
C
Figure 18. Overload Protection (OLP)
F B
V
conditions
FB
(
t
I
2
)
D E LA Y
from 3V to 4.5V with 5µA current source.
t
1
•
V
DELAY
(
t
1
)
;
t
12
) starts to charge C
= C
I
D E L A Y
for
Overload Protection
FB
FB
×(V(t
=
5
increases until it reaches
transformers,
m
A
2
)-V(t
,
LIM
V
(
, the output voltage
t
FB
1
1
)) / I
)
). If V
=
3
DELAY
V
FB
,
V
slowly up to
FB
(
t
2
inductors,
)
exceeds
=
t
2
4
5 .
V
t
9
6. Burst Operation: To minimize the power dissipation
in standby mode, the FSQ211 enters burst mode
operation. As the load decreases, the feedback voltage
decreases. The device automatically enters burst mode
when the feedback voltage drops below V
At this point, switching stops and the output voltages
start to drop. This causes the feedback voltage to rise.
Once is passes V
The feedback voltage falls and the process repeats.
Burst mode operation alternately enables and disables
switching of the power MOSFET to reduce the switching
loss in the standby mode.
I
0.55V
Vo
V
LIM
V
0.7V
I
V
ds
ds
FB
set
o
Drain current
Figure 21. Burst Operation Function
V
Figure 20. Burst Operation Block
fb
4
Figure 19. Internal Soft-Start
2.14ms
5µA
BURH
400µA
(0.70V), switching starts again.
OSC
7steps
S
R
0.70V
/0.55V
Burst Operation Block
Q
BURL
www.fairchildsemi.com
DR IVE R
GATE
(0.55V).
on/off
t
t