Datasheet
MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
______________________________________________________________________________________ 17
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
R
DS(ON)1
R
DS(ON)1
R
SENSE
SENSE GATE1 GATE2 OUT
ISC
IN
V
IN
MAX5943B–MAX5943E
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
SENSE GATE1
OR_ADJONQ1GNDLATCH
GATE2 OUTIN
MAX5943A
TIM
ON
ILIM
FAULT
15mΩ
SI7958DP SI7958DP
SENSE GATE1
OR_ADJONQ1GNDLATCH
GATE2 OUTIN
MAX5943A
TIM
ON
ILIM
FAULT
15mΩ
SI7958DP SI7958DP
SENSEA GATE1A GATE2A OUTAINA
MAX5944
ONA
ONQ1
GND
ONB
FAULTA
FAULTB
30mΩ
SI7958DP SI7958DP
30mΩ
IRF7478 IRF7478
MAX5033
SGND
V
IN
ON
FB
GND
VD
IN4148 IN4148
IN4148
BST
LX
PHY
POWER OUT
CABLE
ON
NOT
SLEEP
CURRENT-LIMIT
SENSE
PORT 1
SENSE
PORT 0
SENSE
CABLE
POWER
SOURCE
BATTERY-
POWER
SOURCE
IN4148
CPA SENSE
PORT 0
PORT 1
SENSEB GATE1B GATE2B OUTBINB