MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
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The programmable timeout of the MAX5943 allows the
use of MOSFETs with low power ratings. A MOSFET
typically withstands single-shot pulses with higher dis-
sipation than the specified package rating.
A single-port FireWire protective circuit employing the
MAX5943A has been UL recognized as a result of
extensive safety testing by Underwriters Laboratories. It
is the circuits themselves, not any individual component
thereof, that are UL recognized. The circuit is further
described in Application Note 3984—
UL Recognized,
IEEE 1394 Single- and Dual-Port FireWire Protective
Circuits
available at www.maxim-ic.com/appnotes.cfm/
appnote_number/3984.
The circuit provides:
• 2.5A (adjustable) current limiting to the load at initial
connection or in overload fault condition
• 2ms (adjustable) current-limit timeout before load
disconnect for excessive load current
• Automatic-restart attempts after a fault shutdown
condition
• <0.8% current-limited duty cycle in continuous fault
condition
• 6.5V undervoltage shutdown protection
• Low-drop ORing in multiple power-source applica-
tions, and
• Fault reporting
Figure 13. Power Dissipated Across MOSFETs During a Short-
Circuit Fault for MAX5943B–MAX5943E
Figure 14. Two-Port FireWire Power Provider Using MAX5943A and MAX5944
