FSDH0265RL_NL Fairchild Semiconductor, FSDH0265RL_NL Datasheet - Page 11

• Manufacturer Part Number: FSDH0265RL_NL
• Manufacturer: Fairchild Semiconductor

Specifications of FSDH0265RL_NL

• Power Switch Family: FSDH0265
• Power Switch On Resistance: 5Ohm
• Output Current: 1.3A
• Number Of Outputs: Single
• Mounting: Surface Mount
• Supply Current: 3mA
• Package Type: LSOP
• Operating Temperature (min): -25C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Commercial
• Pin Count: 8
• Power Dissipation: 1.56W
• Lead Free Status / Rohs Status: Compliant

Cfb from 3V to 6V with 5uA.
4.2 Thermal Shutdown (TSD) : The Sense FET and the
control IC are integrated, making it easier for the control IC
to detect the temperature of the Sense FET. When the tem-
perature exceeds approximately 140°C, thermal shutdown is
activated.
4.3 Abnormal Over Current Protection (AOCP) :
Even though the FPS
and current mode PWM feedback, these are not enough to
protect the FPS
transformer pin short occurs. In addition to start-up, soft-
start is also activated at each restart attempt during auto-
restart and when restarting after latch mode is activated. The
FPS
Vcc
OLP
8V
6V
3V
Vsense
Vfb
TM
t
1 t
t
2
1
COM PARATOR
COM PARATOR
=
=
has an internal AOCP (Abnormal Over Current Pro-
V
C
PW M
FPS switching
−
AOCP
AOCP
fb
RC
(
1
V
Figure 7. AOCP Function & Block
fb
1 (
t
Delay current (5uA) charges the Cfb
Figure 6. Over load protection
In
2 t
+
LEB
TM
I
1 (
t
delay
) 2
−
−
when a secondary side diode short or a
V
V
(
R
(
TM
t
t
) 1
)) 1
);
;
V
has OLP (Over Load Protection)
I
CLK
delay
(
t
) 1
S
=
R
=
5
3
uA
V
,
,
3 t
V
Q
R
1 (
t
=
+
2
8 .
t
) 2
K
−
Ω
V
,
C
(
t
Following Vcc
) 1
fb
Out Driver
=
=
3
4 t
C
V
fb
_
fig
Rsense
2 .
Drain
t
tection) circuit as shown in figure 7. When the gate turn-on
signal is applied to the power Sense FET, the AOCP block is
enabled and monitors the current through the sensing resis-
tor. The voltage across the resistor is then compared with a
preset AOCP level. If the sensing resistor voltage is greater
than the AOCP level, pulse by pulse AOCP is triggered
regardless of uncontrollable LEB time. Here, pulse by pulse
AOCP stops Sense FET within 350nS after it is activated.
4.4 Over Voltage Protection (OVP) : In case of malfunc-
tion in the secondary side feedback circuit, or feedback loop
open caused by a defect of solder, the current through the
opto-coupler transistor becomes almost zero. Then, Vfb
climbs up in a similar manner to the over load situation, forc-
ing the preset maximum current to be supplied to the SMPS
until the over load protection is activated. Because excess
energy is provided to the output, the output voltage may
exceed the rated voltage before the over load protection is
activated, resulting in the breakdown of the devices in the
secondary side. In order to prevent this situation, an over
voltage protection (OVP) circuit is employed. In general,
Vcc is proportional to the output voltage and the FPS
Vcc instead of directly monitoring the output voltage. If
V
mination of the switching operation. In order to avoid undes-
ired activation of OVP during normal operation, Vcc should
be properly designed to be below 19V.
5. Soft Start : The FPS
that increases the feedback voltage together with the Sense
FET current slowly after it starts up. The typical soft start
time is 15msec, as shown in figure 8, where progressive
increments of Sense FET current are allowed during the
start-up phase. The pulse width to the power switching
device is progressively increased to establish the correct
working conditions for transformers, inductors, and capaci-
tors. The voltage on the output capacitors is progressively
increased with the intention of smoothly establishing the
required output voltage. It also helps to prevent transformer
saturation and reduce the stress on the secondary diode.
2.15A
0.98A
CC
Drain current
exceeds 19V, OVP circuit is activated resulting in ter-
[A]
1mS
15steps
TM
has an internal soft start circuit
Current limit
FSDH0265RN, FSDM0265RN
TM
uses
11
t