+48V Quad Hot-Swap Controllers For

Power-Over-LAN

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13

A second comparator with a detection threshold of

purpose of this comparator is to rapidly discharge the

gate when a momentary current peak overstresses the

external FET helping the regulation to act more rapidly.

The sense resistor is also used to detect an open-circuit

or low-current condition with a typical threshold of 3mV.

Open-Circuit Detection

The MAX5913/MAX5914 detect when a port has low

current or is open circuit, and turn off the switch to that

port. After the switch is turned on and the Power-OK

conditions are met, the open-circuit detector is enabled

after a 900ms delay. The open-circuit voltage threshold

is set at 3mV across the current-sense resistor. Drive

OCEN high to enable open-circuit detectors for all four

ports. Drive OCEN low to disable the detectors. Each

port has an open-circuit flag that can be read from

STAT_ outputs when the STATOUT is low. STAT_ output

high indicates that the switch is latched off due to an

open-circuit condition on that port. To reset the latch

pull ON_ low and then high to restart (Table 1).

Output Voltage Sense and Power-OK

The MAX5913/MAX5914 sense the output voltage of

the port at the source of the external MOSFET switch.

FDT3612

N

RTIM

+12V

+3.3V

DIGITAL

INTERFACE

OUTPUTS

DIGITAL

INTERFACE

INPUTS

DGND

AGND

RLYD1

RLYD4

CSP1

DRAIN1

OUT1

1.0

µF

CSP4

DRAIN4

GATE4

OUT4

2k

Ω

0.33

Ω

100

Ω

100

Ω

0.33

Ω

1k

Ω

GATE1

FAULT

STAT1

STAT2

STAT3

STAT4

PORT 1

ON1

ON2

ON3

ON4

RLYON1

RLYON2

RLYON3

RLYON4

OCEN

RTRYEN

STATOUT

DC

MAX5913

FDT3612

N

K4

NO

K1

NO

PORT 4

1

µF

Figure 5. Typical Application Circuit