SP2525A Datasheet, PDF (8/10 Pages) Sipex Corporation – USB High-Side Power Switch

SP2525A
Single Channel USB Power Distribution Switch
APPLICATION INFORMATION
ERROR FLAG
The Error Flag is an open-drained output of an
N-channel MOSFET, the FLG output is pulled
low to signal the following fault conditions:
input undervoltage, output current limit, and
thermal shutdown.
CURRENT LIMIT
The current limit threshold is preset internally.
It protects the output MOSFET switches from
damage resulting from undesirable short
circuit conditions or excess inrush current,
which is often encountered during hot plug-in.
The low limit of the current limit threshold of
the SP2525A allows a minimum current of
0.5A through the MOSFET switches. A current
limit condition will signal the Error Flag.
THERMAL SHUTDOWN
When the temperature of the SP2525A
exceeds 135ºC for any reasons, the thermal
shutdown function turns off the MOSFET
switch and signals the Error Flag. A hysteresis
of 10ºC prevents the MOSFETs from turning
back on until the chip temperature drops
below 125ºC.
SUPPLY FILTERING
A 0.1μF to 1μF bypass capacitor from IN to
GND, located near the device, is strongly
recommended to control supply transients.
Without a bypass capacitor, an output short
may cause ringing on the input (from supply
lead inductance) which can damage internal
control circuitry.
TRANSIENT REQUIREMENTS
USB supports dynamic attachment (hot
plugin) of peripherals. A current surge is
caused by the input capacitance of a
downstream device. Ferrite beads are
recommended in series with all power and
ground connector pins. Ferrite beads reduce
EMI and limit the inrush current during hot-
attachment by filtering high-frequency signals.
SHORT CIRCUIT TRANSIENT
Bulk capacitance provides the short-term
transient current needed during a hot-
attachment event. A 33μF/16V tantalum or a
100μF/ 10V electrolytic capacitor mounted
close to the downstream connector at each
port should provide sufficient transient drop
protection.
PRINTED CIRCUIT LAYOUT
The Power circuitry of USB printed circuit
boards requires a customized layout to
maximize thermal dissipation and to minimize
voltage drop and EMI.
INPUT AND OUTPUT
The independent solid state switch connects
the IN pin to the OUT pin when enabled by a
logic signal at EN. The IN pin is the power
supply connection to the internal circuitry and
the drain of the output MOSFET. The OUT pin
is the source for the MOSFET. Typically, the
current in USB application will flow through
the switch from IN to OUT towards the load. If
VOUT is greater than VIN when a switch is
enabled, the current will flow from OUT to the
IN pin because the MOSFET channels are
bidirectional when switched on. The output
source is allowed to be externally forced to a
higher voltage than its input without causing
unwanted current flow when the output is
disabled.
TEST CIRCUIT
© 2011 Exar Corporation
8/10
Rev. 2.1.0