AIC1527
PIN 10,14:GND
- Chip power return, Connect both
pins to ground.
PIN12(16):OUTC(A) -Channel C(A) MOSFET
switch output.
PIN15: IN(A/B) - Channel A and B power supply
input.
PIN 11:IN(C/D) - Channel C AND D power supply
input.
n
APPLICATION INFORMATIONS
l
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.
switches is independent of each other in the case of
overcurrent fault.
l
Supply Filtering
A 0.1uF to 1uF 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 sufficient ringing on the
input (from supply lead inductance) to damage internal
control circuitry.
l
Current Limit
The current limit threshold is preset internally. It
protects the output MOSFET switches from damage
due to undesirable short circuit conditions or excess
inrush current often encountered during hot plug-in.
The low limit of the current limit threshold of the
AIC1527 allows a minimum current of 0.5A through the
MOSFET switches. A current limit condition will signal
the error flag.
l
Transient Droop Requirements
USB support dynamic attachment (hot plug-in) of
peripherals. A current surge is caused by the input
capacitance of 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.
l
Thermal Shutdown
When the chip temperature exceeds 135°C for any
reason other than overcurrent fault of either one of the
four MOSFET switches, the thermal shutdown
function turns off all MOSFET switches and signal the
error flag. A hysteresis of 10
℃
prevents the MOSFETs
from turning back on until the chip temperature drops
to below 125
℃
. However, if thermal shutdown is
triggered by chip temperature rise due to 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 four
l
Short Circuit Transient
Bulk capacitance provides the short-term transient
current needed during a hot-attachment event. With a
33uF, 16V tantalum or 100uF, 10V electrolytic
capacitor mounted close to downstream connector
per port should provide transient drop protection.
l
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.
DS-1527-00
May 31, 00
7
AIC [ ANALOG INTERGRATIONS CORPORATION ]
