SP2526A Datasheet, PDF (7/9 Pages) Sipex Corporation – Dual USB High-Side Power Switch

SP2526A
Dual Channel USB Power Distribution Switch
APPLICATION INFORMATION
ERROR FLAG
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 SP2526A allows a minimum current of
0.6A through the MOSFET switches. A current
limit condition will signal the Error Flag.
THERMAL SHUTDOWN
When the chip temperature exceeds 135ºC for
any reason other than overcurrent fault of
either one of the two MOSFETs, the thermal
shutdown function turns off both MOSFET
switches and signals the error flag. A
hysteresis of 10ºC prevents the MOSFETs from
turning back on until the chip temperature
drops below 125ºC. However, if thermal
shutdown is triggered by chip temperature rise
resulting from overcurrent fault condition of
either one of the MOSFET switches, the
thermal shutdown function will only turn off
the switch that is in overcurrent condition and
the other switch can still remain its normal
operation. In other words, the thermal
shutdown function of the two switches is
independent of each other in the case of
overcurrent fault.
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.
TEST CIRCUIT
© 2011 Exar Corporation
7/9
Rev. 2.1.0