MAX5915(2002) データシートの表示（PDF） - Maxim Integrated
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MAX5915 Datasheet PDF : 25 Pages
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Dual PCI 2.2 Hot-Swap Controllers
+12V
UVLO THRESHOLD
+12VIN
3.3VAUX UVLO THRESHOLD
3.3VAUXIN
ON_
AUXON_
+12VO_
-12VO_
5VO_
3.3VO_
3.3VAUXO_
TIMING NOT TO SCALE
PGOOD_
Figure 1. Startup Waveforms
tSTART
able all of the affected channel outputs, auxiliary and
main. A fault condition occurs when the output voltage
falls below the set undervoltage threshold or the output
current reaches the overcurrent threshold. When a fault
occurs, all supplies of the affected channel are dis-
abled after a time period tDELAY. All outputs are auto-
matically restarted after a time equal to tRESTART. This
reset is built into both the MAX5915/MAX5916.
Current Limits
All supplies are protected against output overcurrent or
short-circuit conditions. The MAX5915 and MAX5916
employ a “brickwall” current limit on the +3.3V and +5V
supplies and a current-foldback scheme on the ±12V
and +3.3V auxiliary supplies.
Brickwall
A brickwall current limit protects the +3.3V and +5V
main supplies by limiting the load current. The external
sense resistors and the current-limit threshold set the
brickwall current limits. A fault occurs when the load
current reaches the brickwall limit. The main outputs
shut down after tDELAY if the fault remains. The brick-
wall feature limits inrush current caused by positive
supply voltage steps.
Foldback
The ±12V and +3.3V auxiliary supplies employ an inter-
nal current-foldback scheme. The MAX5915/MAX5916
gradually limit the load current once the current-fold-
back threshold is reached. If the overcurrent condition
lasts longer than a fast transient, the output current is
reduced to the foldback current limit and remains at
that level for tDELAY unless the overcurrent condition is
cleared. See the Typical Operating Characteristics.
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