TOP414GN Datasheet, PDF (5/16 Pages) Power Integrations, Inc. – Three-terminal DC to DC PWM Switch

TOP412/414
VIN
VIN
DRAIN
0
VOUT
0
IOUT
0
VC
0
IC 0
12
812
81
•••
•••
12
812
81
•••
•••
45 mA
VC(reset)
1
2
3
4
1
PI-1119-110194
Figure 6. Typical Waveforms for (1) Normal Operation, (2) Auto-restart, (3) Latching Shutdown, and (4) Power Down Reset.
CONTROL pin. V regulation changes from shunt mode to
C
the hysteretic auto-restart mode described above. When the
fault condition is removed, the power supply output becomes
regulated, V regulation returns to shunt mode, and normal
C
operation of the power supply resumes.
Latching Shutdown
The output overvoltage protection latch is activated by a high-
current pulse into the CONTROL pin. When set, the latch
turns off the TOPSwitch output. Activating the power-up
reset circuit by removing and restoring input power, or
momentarily pulling the CONTROL pin below the power-up
reset threshold resets the latch and allows TOPSwitch to
resume normal power supply operation. V is regulated in
C
hysteretic mode when the power supply is latched off.
Over-Temperature Protection
Temperature protection is provided by a precision analog
circuit that turns the output MOSFET off when the junction
temperature exceeds the thermal shutdown temperature
(typically 145 °C). Activating the power-up reset circuit by
removing and restoring input power or momentarily pulling the
CONTROL pin below the power-up reset threshold resets the
latch and allows TOPSwitch to resume normal power supply
operation. V_C is regulated in hysteretic mode when the power
supply is latched off.
High-voltage Bias Current Source
This current source biases TOPSwitch from the DRAIN pin and
charges the CONTROL pin external capacitance (C_T) during
start-up or hysteretic operation. Hysteretic operation occurs
during auto-restart and latched shutdown. The current source
is switched on and off with an effective duty cycle of
approximately 35%. This duty cycle is determined by the ratio
of CONTROL pin charge (I_C) and discharge currents (I_CD1 and
I ). This current source is turned off during normal operation
CD2
when the output MOSFET is switching.
5 ^A
4/99