AAT4625
USB Single-Channel Power Switch
Reverse Voltage
Hot-Plug Applications
The AAT4625 is designed to control current flowing
from IN to OUT. If a voltage is applied to OUT
which is greater than that on IN, a large reverse
current may flow, potentially damaging the device.
Application circuit cards with a high inrush current
potential can be limited by use of the AAT4625.
The AAT4625 has both slew rate limited turn-on
characteristics and a current limit controlled output
which make it ideally suited for power port hot-plug
applications. A host power back plane or hot-plug
receptacle may be sensitive to short duration, high
power surges. The AAT4625 will turn on in a linear
ramping fashion and regulate the inrush current
within the specified current limit for the device. The
error flag usually will not be affected during appli-
cation turn-on, since the 10ms flag blanking time is
intended for these types of events. If an application
turn-on current surge exceeds 10ms, an RC delay
filter may be added to the flag output to prevent the
system from receiving an error during the start-up
sequence (see Figure 2).
Under-Voltage Lockout
The AAT4625 has been designed with an under-volt-
age lockout control circuit. The under-voltage lock-
out prevents the output MOSFET device from turn-
ing on until VIN exceeds the typical UVLO threshold
of 2.3V. During operation, the device will automati-
cally shut down if VIN falls below the UVLO threshold
and the fault flag will be toggled.
Cable / Connector
to Hot-Plug Port
AAT4625
Card
Application
Circuit
v+
1
2
3
4
8
EN
OUT
IN
VBUS
7
6
5
FLG
GND
NC
OUT
NC
Hot-Plug
Receptacle
C
BULK
(120μF)
0.1μF
GND
GND
Inrush Current Protected
Application Card
Figure 2: AAT4625 Inrush Current Protected Application.
voltage and current transient events will occur.
PCB Layout Information
Proper PCB layout can help reduce the effects of
transient events. PCB trace resistance will affect
overall circuit transient response; in addition, small
voltage drops will be incurred.
In order to obtain maximum performance from the
AAT4625, very careful consideration must be given
to the printed circuit board layout. In most port
power switch and port protection applications, high
10
4625.2006.04.1.2
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
