3V to 12V Current-Limiting Hot Swap Controllers

with Autoretry, DualSpeed/BiLevel Fault Protection

20

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The ON and INC comparator inputs and the STAT and

OUTC can be pulled to voltages up to 14V indepen-

and not be turned on through the internal protection

diodes. In some applications, it is useful to use connec-

tors with staggered leads. In Figure 14, the ON pin

forces the removable board to be powered up only

when all connections are made.

used to sustain the input voltage required for the device

to operate during a short-circuit condition on the board.

When a short occurs, the main system power supply

could collapse and the MAX4273 will not have enough

voltage to keep the gate drive operational and turn off

the external MOSFET. If the fault is not removed, the

system could remain in a sustained short-circuit state.

Connect a 1µF capacitor from the AUXVCC pin to GND.

This capacitor will deliver the necessary energy to the

gate drive until the MOSFET is turned off and the main

through an internal switch during normal operation.

Maximum Load Capacitance

The MAX4271/MAX4272/MAX4273 can be used on the

backplane to regulate current upon insertion of a

removable card (Figure 16). This allows multiple cards

with different input capacitance to be inserted into the

same slot even if the card doesn’t have on-board hot-

swap protection.

The MAX4271/MAX4272/MAX4273 current-limiting fea-

ture is active during the startup period set by CTIM.

expired (timed out), the load capacitance has to be

charged or a fault condition is detected. To ensure

the time required to charge the board capacitance. The

maximum load capacitance is calculated as follows:

Input Transients

inrush and fault conditions. When a short condition

occurs on the board, the fault current can be higher

than the fast comparator current limit. The gate voltage

Figure 12. Power-On Reset

OUTC

RESET

µP

INC

LLMON

IN

SENSE

GATE

MAX4273

Figure 14. Fail-Safe Connector

IN

ON

BACKPLANE

10k

1M

RESET

MAX4271

MAX4272

MAX4273

SENSE GATE

REMOVABLE

CARD

Figure 13. Power-On Reset and Temperature

GND

LLMON

OUTC

ON

REF

IN

INC

SENSE

GATE

NTC

MAX4273