Current-Limited Switch for Two USB Ports
Driving Inductive Loads
A wide variety of devices (mice, keyboards, cameras,
and printers) can load the USB port. These devices com-
monly connect to the port with cables, which can add an
inductive component to the load. This inductance caus-
es the output voltage at the USB port to ring during a
load step. The MAX1930 is capable of driving inductive
loads, but avoid exceeding the device’s absolute maxi-
mum ratings. Usually the load inductance is relatively
small, and the MAX1930’s input includes a substantial
bulk capacitance from an upstream regulator, as well as
local bypass capacitors, limiting overshoot. If severe
ringing occurs due to large load inductance, clamp the
MAX1930 output below 6V and above -0.3V.
INPUT
1 F
IN
OUT
OUTPUT
*
0.1 F
MAX1930
OVERCURRENT
OUTPUT
OFF
ON
EN
GND
*
USB SPECIFICATIONS REQUIRE
A HIGHER VALUE CAPACITOR.
Chip Information
Figure 2. Typical Application Circuit
TRANSISTOR COUNT: 715
PROCESS: BiCMOS
ture. If the fault condition is not removed, the thermal-
overload protection circuitry activates (see the Thermal
Shutdown section). Wide power-bus planes connected
to IN and OUT and a ground plane in contact with the
device help dissipate additional heat.
6
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