USB Dual-Channel Power Switch
Functional Block Diagram
AAT4626
IN
Over-
Temperature
Protection
Under-
Voltage
Lockout
OUTA
OUTB
ENB (ENB)
ENA (ENA)
1.2V
Reference
Current
Limit
Over-Temp Protection
Under-Voltage Lockout
Current Limit
FLGA
Over-Temp Protection
Under-Voltage Lockout
Current Limit
FLGB
Functional Description
The AAT4626 is a dual integrated MOSFET load
switch with a fixed level current limit, over-temper-
ature protection, level shifted inputs, and a fault
flag for each switch. The current limit control is
combined with an over-temperature thermal limit
circuit to provide a comprehensive system to pro-
tect the load switch under short-circuit or other
adverse operating conditions. The AAT4626 is ide-
ally 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 a pre-
set internal threshold level. The minimum current
limit threshold characteristic 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-temper-
ature protection circuit to activate.
If the current limit or over-temperature protection
circuits are active for more than ten milliseconds,
4626.2006.05.1.2
the system will be informed via the FAULT flag.
The ten millisecond fault blanking delay allows the
AAT4626 to be turned on into large capacitive
loads without activating the FAULT flags. The
open drain FAULT outputs can be connected
directly to system controllers driven by voltage lev-
els less than the IN pin voltage without additional
level shifting circuitry.
Each of the two load switches is turned on and off
by applying a logic level signal to the EN(A/B) pin.
The AAT4626 enable function is available in both
active high and active low logic level versions. The
AAT4626 typically consumes 20µA when operat-
ing; when off, the device draws less than 1µA. In
the off state, current is prevented from flowing
between the input and output on each respective
channel. The EN(A/B) function has logic level
thresholds that allow the AAT4626 to be TTL com-
patible and may also be controlled by 2.5V to 5.0V
CMOS circuits. The voltage level on either
EN(A/B) or FAULT(A/B) should not exceed the
input supply level present on the IN pin.
7
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
