FSEZ1216 Fairchild Semiconductor, FSEZ1216 Datasheet - Page 12

• Manufacturer Part Number: FSEZ1216
• Description: The primary-side PWM integrated Power MOSFET, FSEZ1216, significantly simplifies power supply design that requires CV and CC regulation capabilities
• Manufacturer: Fairchild Semiconductor

© 2009 Fairchild Semiconductor Corporation
FSEZ1216 • Rev. 1.0.1
Leading-Edge Blanking (LEB)
At the instant the MOSFET is turned on, there is a high-
current spike through the MOSFET, caused by primary-
side capacitance and secondary-side rectifier reverse
recovery. Excessive voltage across the R
lead to premature turn-off of MOSFET. FSEZ1216
employs an internal leading-edge blanking (LEB) circuit.
To inhibit the PWM comparator for a short time after the
MOSFET is turned on. External RC filtering is not required.
Startup
Figure 29 shows the typical startup circuit and
transformer
application. Before FSEZ1216 begins switching, it
consumes only startup current (typically 10μA) and the
current supplied through the startup resistor charges the
V
of 16V (V
current consumed by FSEZ1216 increases to 3.5mA.
Then, the power required for FSEZ1216 is supplied from
the transformer auxiliary winding. The large hysteresis
of V
small capacitor for V
Protections
The FSEZ1216 has several self-protective functions,
such
Temperature
protection.
implemented as auto-restart mode. Once the fault
condition occurs, switching is terminated and the
MOSFET remains off. This causes V
reaches the V
consumed by FSEZ1216 reduces to the startup current
(typically 10µA) and the current supplied startup resistor
charges the V
on voltage of 16V, FSEZ1216 resumes its normal
operation. In this manner, the auto-restart alternately
DD
DD
AC Line
capacitor (C
1
2
3
4
provides more holdup time, which allows using a
as
CS
COMR
COMI
COMV
FSEZ1216
DD-ON
Over-Voltage
All
Figure 29. Startup Circuit
DD
auxiliary
C
DRAIN
SGND
), FSEZ1216 begins switching, and the
DD
D L
VDD
Protection
DD
capacitor. When V
VS
the
). When V
turn-off voltage of 5V, the current
DD
8
7
6
5
V
+
.
-
D L
protections
winding
Protection
DD
(OTP),
reaches turn-on voltage
C
R
D D
STAR T
D
D D
for
DD
DD
except
reaches the turn-
to fall. When V
and
(OVP),
a
CS
resistor can
FSEZ1216
OTP
brownout
N
R
R
Np
Over-
A
S1
S2
are
DD
12
enables and disables the switching of the MOSFET until
the fault condition is eliminated (see Figure 30).
Meanwhile, OTP is latch mode protection, which is reset
when V
power line.
V
V
voltage conditions. If the V
open feedback condition, OVP is triggered. The OVP
has a de-bounce time (typcal 250µs) to prevent false
trigger by switching noise. It also protects other
switching devices from over voltage.
Over-Temperature Protection (OTP)
A built-in temperature-sensing circuit shuts down PWM
output if the junction temperature exceeds 140°C.
Brownout Protection
FSEZ1216 detects the line voltage using auxiliary
winding voltage since the auxiliary winding voltage
reflects the input voltage when the MOSFET is turned
on. The V
is turned on and brownout protection is triggered if the
current out of the VS pin is less than I
180μA) during the MOSFET conduction.
Pulse-by-Pulse Current Limit
When the sensing voltage across the current sense
resistor exceeds the internal threshold of 1.4V, the
MOSFET is turned off for the remainder of switching
cycle. In normal operation, the pulse-by-pulse current
limit is not triggered since the peak current is limited by
the control loop.
3.5mA
DD
DD
10µA
V
V
16V
5V
DS
DD
Operating Current
Over-Voltage Protection (OVP)
over-voltage protection prevents damage from over-
DD
Power
Figure 30. Auto-Restart Operation
S
On
is fully discharged by un-plugging the AC
pin is clamped at 1.15V while the MOSFET
Operation
Normal
Occurs
Fault
Situation
DD
Fault
voltage exceeds 28V by
Fault Removed
VS-UVP
Operation
www.fairchildsemi.com
Normal
(typical