MAX4370 Просмотр технического описания (PDF) - Maxim Integrated

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MAX4370

Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection

Maxim Integrated 

Current-Regulating Hot-Swap Controller with

DualSpeed/BiLevel Fault Protection

Status Output

The status output is an open-drain output that goes low

when the part is:

1) in start-up

2) forced off (on = GND)

3) in an overcurrent condition, or

4) latched off.

STAT is high only if the part is in normal mode and no

faults are present (Table 1). Figure 4 shows the STAT

timing diagram.

Over/Undervoltage Lockouts

The undervoltage lockout prevents the MAX4370 from

turning on the external MOSFET until the input voltage

at VIN exceeds the lockout threshold (2.25V min) for at

least 150ms. The undervoltage lockout protects the

external MOSFET from insufficient gate drive voltage.

The 150ms timeout ensures that the board is fully

plugged into the backplane and that VIN is stable.

Voltage transients at VIN with voltages below the UVLO

will reset the device and initiate a start-up sequence.

The device also features a gate overvoltage lockout

that prevents the device from restarting after a fault

condition if the discharge has not been completed.

VGATE must be discharged to below 0.1V before

restarting. Since the MAX4370 does not monitor the

output voltage, a start-up sequence can be initiated

while the board capacitance is still charged.

Gate Overvoltage Protection

Newer-generation MOSFETs have an absolute maxi-

mum rating of ±8V for the gate-to-source voltage (VGS).

To protect these MOSFETs, the MAX4370 limits the

gate-to-drain (VGD) to +7.5V with an internal zener

diode. No protection is provided for negative VGD. If

GATE can be discharged to GND faster than the output

voltage, an external small-signal protection diode (D1)

can be used, as shown in Figure 5.

VIN

ON

OV

1.2V

CTIM

OV

VIN

STAT

OV

FAULT

CONDITION

OR ON

FALLING EDGE

NO FAULT CONDITIONS

PRESENT

Figure 4. Status Output (STAT) Timing Diagram

MAX4370

VIN

RSENSE

VSEN

GATE DRIVE

CHARGE PUMP

VGD

GATE

VGS

D1

M1

N

VOUT

CBOARD

Figure 5. External Gate-Source Protection

Table 1. Status Output Truth Table

PART IN

START-UP

Yes

No

No

No

No

X = Don’t care

ON PIN

X

Low

High

High

High

OVERCURRENT

CONDITION ON VIN

X

X

Yes

No

No

PART IN LATCHED-OFF MODE

DUE TO OVERCURRENT

CONDITION

X

X

X

Yes

No

STAT PIN

(STATUS)

Low

Low

Low

Low

High

10 ______________________________________________________________________________________

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