top412 Power Integrations, Inc., top412 Datasheet - Page 5

• Manufacturer Part Number: top412
• Description: Three-terminal Dc To Dc Pwm Switch
• Manufacturer: Power Integrations, Inc.

Figure 6. Typical Waveforms for (1) Normal Operation, (2) Auto-restart, (3) Latching Shutdown, and (4) Power Down Reset.
CONTROL pin. V
the hysteretic auto-restart mode described above. When the
fault condition is removed, the power supply output becomes
regulated, V
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
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
DRAIN
V OUT
I OUT
V IN
V C
I C
C
V IN
regulation returns to shunt mode, and normal
0
0
0
0
0
C
regulation changes from shunt mode to
1
1
1
2
2
• • •
• • •
C
is regulated in
8
8
1
1
2
2
2
• • •
• • •
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
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
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
I
when the output MOSFET is switching.
CD2
). This current source is turned off during normal operation
8
8
1
1
3
C
is regulated in hysteretic mode when the power
45 mA
C
4
) and discharge currents (I
TOP412/414
V C(reset)
1
PI-1119-110194
4/99
T
A
) during
CD1
5
and