AAT4625_06 Datasheet, PDF (10/15 Pages) Advanced Analogic Technologies – USB Single-Channel Power Switch

AAT4625
USB Single-Channel Power Switch
Reverse Voltage
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.
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 V_IN exceeds the typical UVLO threshold
of 2.3V. During operation, the device will automati-
cally shut down if V_IN falls below the UVLO threshold
and the fault flag will be toggled.
Hot-Plug Applications
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).
Cable / Connector
to Hot-Plug Port
V_BUS
Hot-Plug
Receptacle
GND
v+
0.1μF
AAT4625
1 _EN
OUT ⁸
2 _FLG
IN ⁷
3 _{GND OUT} 6
4 _NC
NC ⁵
GND _{Inrush Current Protected}
Application Card
CBULK
(120μF)
Card
Application
Circuit
Figure 2: AAT4625 Inrush Current Protected Application.
PCB Layout Information
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
voltage and current transient events will occur.
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.
10
4625.2006.04.1.2