Electronic Resettable Fuse
Functional Block Diagram
AAT4680
IN
Over-Temperature
Protection
OUT
Under-Voltage
Lockout
Current
Limit
FAULT
3ms Blanking
GND
Functional Description
The AAT4680 is a single channel electronic reset-
table fuse that protects against short-circuit condi-
tions by current limiting to a preset level. A patent-
ed fast acting current limit loop limits load current in
a fraction of a microsecond and instantly resets to
low impedance once the short-circuit condition is
removed. A current limit condition is reported by the
open drain FAULT output after a three millisecond
blanking interval. The blanking prevents false
reporting during the charging of a capacitive load,
which typically occurs when a load is connected.
The AAT4680 is internally protected from thermal
damage by an over-temperature detection circuit.
If the die temperature reaches the internal thermal
limit, the power device is switched off until the die
temperature cools to a level below the thermal limit
threshold. The device will thermal cycle indefinite-
ly until the over-current condition is removed. The
AAT4680 operates with input voltages ranging from
1.8V to 5.5V which, along with extremely low oper-
ating current, makes it ideal for battery-powered
applications. In cases where the input voltage
drops below 1.8V, the AAT4680 internal MOSFET
is protected from entering the saturated region of
operation by being automatically shut down by an
under-voltage lockout circuit.
The AAT4680 is ideally suited for protection of peri-
pheral ports such as USB, RS232, and parallel
ports.
4680.2006.05.1.2
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AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
