1.8A Current Limited P-Channel Switch
Functional Block Diagram
AAT4601A
IN
OUT
Under-
Voltage
Lockout
Over-Temperature
Protection
FAULT
ON
1.2V
Reference
Current
Limit
SET
Functional Description
The AAT4601A is an integrated MOSFET load
switch with an adjustable current limit, over-tem-
perature protection, level-shifted input, and a fault
flag. The current limit control is combined with an
over-temperature thermal limit circuit to provide a
comprehensive system to protect the load switch
under short-circuit or other adverse operating con-
ditions. The AAT4601A is ideally suited for control
and protection of peripheral ports such as USB,
RS232, and parallel ports.
The current limit and over-temperature circuits will
act independently. The device current limit is acti-
vated when the output load current exceeds an
internal threshold level. The internal current limit
threshold is determined by an external resistor
connected between the SET pin and ground. The
minimum current limit threshold is specified by
I
LIM(MIN)
. If the load switch ambient temperature
becomes excessive or if a short-circuit condition
persists, the die temperature will rise causing the
over-temperature protection circuit to activate.
If a current limit level less than I
LIM(MIN)
is required,
the AAT4601A can be used to operate in foldback
8
current limit mode. To achieve this, an R
SET
value
can be chosen to program a current limit lower
than I
LIM(MIN)
; in this case, when the load current
reaches I
LIM(MIN)
, the current will immediately drop,
limiting at the programmed value.
If the current limit or over-temperature protection
circuits are active for more than 2ms, the system
will be informed via the FAULT flag. The 2ms delay
allows the AAT4601A to be turned on into capaci-
tive loads without activating the FAULT flag. The
open drain FAULT output can be connected direct-
ly to system controllers driven by voltage levels
less than the IN pin voltage without additional level
shifting circuitry.
The load switch is turned off by applying a logic high
level to the ON pin. The AAT4601A typically con-
sumes 12µA when operating; when off, the device
draws less than 1µA. In the off state, current is pre-
vented from flowing between the input and output.
The ON function has logic level thresholds that
allow the AAT4601A to be TTL compatible and may
also be controlled by 2.5V to 5.0V CMOS circuits.
The voltage level on either ON or FAULT should not
exceed the input supply level present on the IN pin.
4601A.2006.05.1.5
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
