top100 Power Integrations, Inc., top100 Datasheet - Page 5

• Manufacturer Part Number: top100
• Description: Three-terminal Off-line 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.
Shutdown/Auto-restart
To minimize TOPSwitch power
dissipation, the shutdown/auto-restart
circuit turns the power supply on and off
at a duty cycle of typically 5% if an out
of regulation condition persists. Loss of
regulation interrupts the external current
into the CONTROL pin. V
changes from shunt mode to the
hysteretic auto-restart mode described
above. When the fault condition is
removed, the power supply output
becomes regulated, V
to shunt mode, and normal 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
DRAIN
V OUT
I OUT
V IN
V C
I C
V IN
0
0
0
0
0
C
regulation returns
1
C
regulation
1
1
2
2
•••
•••
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
the power supply is latched off.
Overtemperature 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
the power supply is latched off.
C
C
is regulated in hysteretic mode when
is regulated in hysteretic mode when
8
8
1
1
2
2
2
•••
•••
8
8
1
1
3
45 mA
High-voltage Bias Current Source
This current source biases TOPSwitch
from the DRAIN pin and charges the
CONTROL pin external capacitance
(C
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
turned off during normal operation when
the output MOSFET is switching.
CD1
T
) during start-up or hysteretic
and I
4
CD2
C
). This current source is
) and discharge currents
TOP100-4
V C(reset)
1
PI-1119-110194
7/96
E
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