XRP2527 - XRP2528
Single/Dual Channel Adjustable Current Power
Distribution Switch
Fig. 28: Current Limit Operation (XRP2527):
VIN=5V, Rload = 10Ω, RSET = 330kΩ
Over-temperature and under voltage lockout
conditions are flagged immediately while the
output over – current condition is reported if
continuously persistent for longer than the
blanking time of 10ms. The blanking time
prevents erroneous reporting of current faults
due to brief output current spikes.
THEORY OF OPERATION
The XRP2527 and XRP2528 devices are
respectively single and dual channel integrated
high-side power distribution switches with
programmable current limit threshold feature.
They can be used in any self or bus powered
USB applications and are compliant with the
latest USB 3.0 specifications. The reverse
current protection feature prevents current to
flow from OUT to IN when the device is
disabled.
Once activated, the error flag signal remains
low until all fault conditions have been
removed and is independent for each
individual channel.
CURRENT LIMIT
I
NPUT & OUTPUT
The current limit feature protects the output
MOSFET switches from damages resulting
from undesirable short circuit conditions or
excess inrush current, which is often
Placing bulk capacitances of at least 47μF and
10μF at the input and output pins respectively
reduces power supply transients under heavy
current load conditions.
encountered
during
hot
plug-in.
Upon
It is important to place a 1μF ceramic bypass
capacitor from IN to GND as close as possible
to the device in order to control supply
transients.
detection of overcurrent condition, the output
current is limited to a constant current limit
threshold value and the output voltage is
reduced accordingly. Triggering the current
limit function is signaled by the Error Flag
after 10ms of blanking time period.
Furthermore, bypassing the output pin with a
0.1μF to 1μF ceramic capacitor improves the
device response to short-circuit transients.
The minimum current limit threshold can be
programmed from 300mA to 1A set via an
external resistor at the RSET pin. If RSET pin
is left floating, then the device is set to USB
3.0 current limit setting. For USB 2.0 current
limit setting, the RSET pin must be tied to
VIN. The current limit threshold value is set
using the resistor at RSET pin by the following
equation:
E
RROR FLAG
The error flag signal (FLGX output pin) is an
open-drain output and is pulled low (active
low) upon detection of the following
conditions:
Over-current condition
Over-temperature condition
Under voltage lockout condition
© 2011 Exar Corporation
9/13
Rev. 1.1.0
EXAR [ EXAR CORPORATION ]
