MAX5916EUI+ Datasheet MAX5916EUI+, MAX5915EUI+T, MAX5916EUI+T | P13-P15

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 disabled after a time period

DELAY

. All outputs are automatically restarted after a

time equal to t

RESTART

. This reset is built into all devices.

Current Limits

All supplies are protected against output overcurrent or

short-circuit conditions. The MAX5915/MAX5915A and

MAX5916/MAX5916A 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 t

DELAY

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

internal current-foldback scheme. The MAX5915/

MAX5915A/MAX5916/MAX5916A gradually limit the load

current once the current-foldback threshold is reached. If

the overcurrent condition lasts longer than a fast tran-

sient, the output current is reduced to the foldback cur-

rent limit and remains at that level for t

DELAY

unless the

overcurrent condition is cleared. See the Typical

Operating Characteristics.

MAX5915/MAX5915A/MAX5916/MAX5916A

Dual PCI 2.2 Hot-Swap Controllers

______________________________________________________________________________________ 13

START

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

MAX5915/MAX5915A/MAX5916/MAX5916A

Input Undervoltage Lockout

UVLO prevents these devices from turning on

internal/external MOSFETs until the input voltage exceeds

the lockout threshold. The UVLO protects the MOSFETs

from insufficient gate-drive voltage. Figure 2 shows that if

an input undervoltage condition exists for more than

DEG,UVLO

, the outputs are disabled and PGOOD_ goes

low immediately. The time delay t

DEG,UVLO

is negative

edge delayed and acts as a deglitch.

Fault Management

When a fault is detected on one of the main outputs, the

MAX5915/MAX5915A/MAX5916/MAX5916A disable the

channel outputs after t

DELAY

. A fault occurs when any of

the output voltages fall below their output undervoltage

threshold or any of the output currents exceed their out-

put overcurrent threshold. PGOOD_ pulls low if a fault

persists for more than t

RESP

. The channel with the fault is

disabled after t

DELAY

. The MAX5915/MAX5916 are avail-

able with a response time of 1.5ms (t

RESP

). The

MAX5915A/MAX5916A offer a response time of 100ns

RESP2

). If the fault is removed before t

DELAY

, the chan-

nel remains on and PGOOD_ pulls high immediately.

Latched Fault Protection

The MAX5915/MAX5915A latch off the appropriate

channel’s main outputs. Toggling +12VIN or ON_

restarts the main outputs. Figure 3 outlines the logic for

the main and auxiliary shutdown control of the

MAX5915, while fault handling is shown in Figures 5

and 6.

Autoretry Fault Protection

The MAX5916/MAX5916A automatically restart the out-

puts after t

RESTART

. The MAX5915/MAX5915A/

MAX5916/MAX5916A handle faults on the auxiliary out-

puts by automatically restarting the appropriate chan-

nel. Figure 4 outlines the logic for the main and auxiliary

shutdown control of the MAX5916, while fault handling

is shown in Figures 6 and 7.

Output Overcurrent

External sense resistors monitor the current on the +5V

and +3.3V outputs, while the +3.3V auxiliary and ±12V

output currents are monitored internally. Figures 5, 6,

and 7 show overcurrent fault management for the

MAX5915/MAX5915A/MAX5916/MAX5916A.

Dual PCI 2.2 Hot-Swap Controllers

14 ______________________________________________________________________________________

ON_

+12VIN

3.3VAUXIN

PGOOD_

AUXON_

+12V UVLO THRESHOLD

3.3VAUX UVLO THRESHOLD

START

DEG.UVLO

+12VO_

5VO_

3.3VO_

3.3VAUXO_

-12VO_

TIMING NOT TO SCALE

Figure 2. Input UVLO Fault Management in the MAX5915/MAX5915A/MAX5916/MAX5916A

Output Undervoltage

The output voltages on all supplies, except the -12V

supply, are monitored for undervoltage. Output under-

voltage fault management is identical to the output

overcurrent fault management. Figures 5, 6, and 7 can

be used to illustrate undervoltage faults on the

MAX5915/MAX5915A/MAX5916/MAX5916A.

Thermal Shutdown Control

The MAX5915/MAX5915A/MAX5916/MAX5916A feature

internal thermal protection. Two thresholds detect when

the device is overheated. If the first threshold is reached,

the channel that is in overcurrent shuts down. If the sec-

ond thermal threshold is reached, the entire device shuts

down. The device cannot be restarted until the thermal

condition is cleared. For the MAX5915, the main chan-

nels turn back on after +12VIN or ON_ is toggled. For the

MAX5916, the main channels turn back on after

RESTART

. The auxiliary channels for the MAX5915/

MAX5915A/MAX5916/MAX5916A restart after t

RESTART

PGOOD_ Operation

The MAX5915/MAX5915A/MAX5916/MAX5916A incor-

porate a PGOOD_ output to report when power is good

to a microprocessor or controller. PGOOD_ remains low

if the auxiliary outputs are not powered, for PCI and

compact PCI systems where the 3.3VAUX is not avail-

able. Connect 3.3VAUXIN to 3.3VIN and connect

AUXON_ to ON_ to allow PGOOD_ to transition high

when the main supplies are available. The open-drain

structure of PGOOD_ requires an external pullup resis-

tor (see the Functional Diagram). Figure 8 shows the

internal logic of the PGOOD_ output.

MAX5915/MAX5915A/MAX5916/MAX5916A

Dual PCI 2.2 Hot-Swap Controllers

______________________________________________________________________________________ 15

DELAY

RESTART

ENABLE_+12VIN

STARTUP_+12VIN

OC_3.3VAUXO_

UV_3.3VAUXO_

RESET

POSITIVE EDGE

TRIGGERED D FLIP-FLOP,

RESET IS ACTIVE LOW

OC_3.3VO_

OC_5VO_

OC_+12VO_

OC_-12VO_

UV_3.3VO_

UV_5VO_

UV_+12VO_

POSITIVE EDGE TRIGGERED D FLIP-FLOP,

RESET IS ACTIVE LOW

HIGH = MAIN SUPPLIES

ARE TURNED OFF

MAIN ON

AUX OFF

HIGH = AUX SUPPLY

TURNED OFF

ENABLE_3.3VAUXIN

STARTUP_3.3VAUXIN

V = INTERNAL SUPPLY LOGIC

GENERATED BY THE 12VIN OR THE

3.3VAUXIN, WHICHEVER IS HIGHER

RESET

SEE TABLE 2 FOR EXPLANATION OF SIGNALS.

Figure 3. Main and Auxiliary Supply Shutdown Control Logic for MAX5915/MAX5915A

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P25

MAX5916EUI+

Mfr. #:

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Manufacturer:

Maxim Integrated

Description:

Hot Swap Voltage Controllers Dual PCI 2.2 Hot Swap Controller

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MAX5916EUI+

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