LTC4261 datasheet(20/74 Pages) AD

20 / 74 page

LTC4283

Rev. B

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APPLICATIONS INFORMATION

where VGS is the gate-to-source voltage of the MOSFET

(positive for an enhancement mode and negative for a

depletion mode transistor) . When using an enhancement

mode transistor, VZ voltage must be kept lower than its

absolute maximum of 16V:

VZ(MAX) = VIN(MAX) + VGS < 16V

In Figure 2b and Figure 3, the voltage drop and power

dissipation in the NPN or the MOSFET may be augmented

by the use of one or more resistors in series with the col-

lector or drain. If an external 12V supply is available on

the application board, it may be used to drive the VIN pin

directly as shown in Figure 4.

Turn-On Sequence

The following conditions must be satisfied before the

turn-on sequence is started. First the voltage at VIN must

exceed the undervoltage lockout level of 8.1V. Next the

internal supply INTVCC must cross its 4V undervoltage

lockout level. This generates a 1.3ms power-on-reset

delay. After the delay times out, the voltages at UVH, UVL

and OV must satisfy UVH > 2.048V, UVL > 1.833V and

OV < 1.406V to indicate that the input power is within the

acceptable range, and EN# must be pulled low. All the

above conditions must be satisfied throughout the dura-

tion of the startup debounce delay of 128ms. If any of the

above conditions is violated during the delay, the delay is

reset and restarted. After the delay expires, if the ON bit

in CONTROL_1 register 0x0A is high, the LTC4283 turns

on the MOSFET. Otherwise, the MOSFET will be turned

on (without additional delay) when the ON bit is set to 1

through the I2C interface. When all turn-on conditions are

satisfied, the FET_ON_STATUS bit in SYSTEM_STATUS

manded on.

Figure 2a. –48V/600W Dual-Feed Hot Swap Controller with LTC4283 (Part One)

750

0.5m

RS1

20k

10k

CE1

4.7nF

CE2

68nF

RE1

18.2k

RE2

1.13M

CUV

100nF

2N5401

100k

100A

10k

100k

CEN

1µF

R10

100k

HZS5C1

100A

10k

RRT

200k

RRB

5.11k

499k

2N5401

R11

5.62k

R12

20k

RTN A

UVH

UVL

–48V B

ADIN1-4

TMR

VEE

SENSE– SENSE+

RAMP

ADIO1-4

LTC4283

DVDT = 0

THERM_TMR = 1

PWRGD_RESET_CNTRL = 1

ILIM = 0001

FB = 11

FB_DIS = 1

LPFB = 1

4283 F02a

EN#

UV = 32.4V

UV RELEASE AT 35.3V

OV = 74.5V

OV RELEASE AT 73.2V

VEE

LTC4371

RTN B

–48V A

LTC4355

1N4148

×2

RTNS

BACKPLANE PLUG-IN

CARD

VEE

×4

VOUTTH

VREF

VEE

BATTERY OPERATED

(SUBJECT TO –36V INPUT STEPS)

LTC4261 Datasheet(PDF) 20 Page - Analog Devices

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