ICE3AS02_05 Datasheet, PDF (14/22 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

F3
ICE3AS02 / ICE3AS02G / ICE3BS02 / ICE3BS02G
Functional Description
gate G10. Maximum current can now be provided to
stabilize V_OUT.
V_FB
4.80V
4.00V
3.40V
EnteringActive LeavingActive
Burst Mode
Burst Mode
1.32V
V_SoftS
t
Blanking Window
5.40V
4.40V
V_CS
t
1.00V
Current limit level during
Active Burst Mode
0.257V
V_VCC
t
3.6.3
Protection Mode (Auto Restart Mode)
In order to increase the SMPS system’s robustness and
safety, the IC provides the Auto Restart Mode as a protection
feature. The Auto Restart Mode is entered upon detection of
the following faults in the system:
• VCC Overvoltage
• Overtemperature
• Overload
• Open Loop
• VCC Undervoltage
• Short Optocoupler
SoftS
C_SoftS
R_SoftS
5k
VCC
C1
4.4V _17V
C11
4.0V
S1
6.5V
Control Unit
&
Spike
G1
Blanking
8.0us
Thermal Shutdown
T_j >140°C
4.8V
FB
C4
&
Auto Restart
G5
Mode
C3
5.4V
Voltage
Reference
8.5V
I_VCC
7.2mA
1.05mA
V_OUT
Max. Ripple < 1%
Figure 17 Signals in Active Burst Mode
Figure 18 Auto Restart Mode
t
The VCC voltage is observed by comparator C1 if 17V is
exceeded. The output of C1 is combined with both the output
of C11 which checks for SoftS<4.0V, and the output of C4
which checks for FB>4.8V. Therefore the overvoltage
detection is can only active during Soft Start
Phase(SoftS<4.0V) and when FB signal is outside the
operating range > 4.8V. This means any small voltage
overshoots of V_VCC during normal operating cannot trigger
t ^{the Auto Restart Mode.}
In order to ensure system reliability and prevent any false
activation, a blanking time is implemented before the IC can
enter into the Auto Restart Mode. The output of the VCC
overvoltage detection is fed into a spike blanking with a time
constant of 8.0µs.
The other fault detection which can result in the Auto Restart
Mode and has this 8.0µs blanking time is the
Overtemperature detection. This block checks for a junction
t
temperature of higher than 140°C for malfunction operation.
Version 1.2
14
02 Sep 2005