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-

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

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

cleared. See the Typical Operating Characteristics.

Dual PCI 2.2 Hot-Swap Controllers

______________________________________________________________________________________

13

ON_

+12VIN

3.3VAUXIN

PGOOD_

TIMING NOT TO SCALE

AUXON_

+12V

UVLO THRESHOLD

3.3VAUX UVLO THRESHOLD

+12VO_

5VO_

3.3VO_

3.3VAUXO_

-12VO_

Figure 1. Startup Waveforms