LTC2913 datasheet(10/22 Pages) AD

10 / 22 page

LTC4368

Rev. B

For more information www.analog.com

VOUT (V)

4365 F03

VIN = 12V, 60V

VIN = 5V

VIN = 2.5V

VIN = 3.3V

TA = 25°C

IGATE = –1µA

APPLICATIONS INFORMATION

The LTC4368 is an N-channel MOSFET controller that pro-

tects a load from overvoltage faults (both positive and

negative) and from overcurrent faults (both forward and

reverse). A typical application circuit using the LTC4368-2

is shown in Figure 2. The circuit provides a low loss con-

nection from VIN to VOUT as long as there are no voltage

or current faults.

Voltages at VIN outside of the 7V to 36V range are

prevented from getting to the load and can be as high as

100V and as negative as –40V. Load currents (including

inrush currents) above 12.5A (forward from VIN to VOUT)

and below –0.75A (reverse from VOUT to VIN) will cause the

load to be disconnected from VIN. The circuit of Figure 2

protects against negative voltages at VIN as shown. Note

that the SOA and voltage requirements are not the same

for the two external MOSFETs. During power-up, the input

MOSFET (M1) will stand off more voltage (up to VIN) than

the output MOSFET (M2). The body diode of M2 will limit

its drain to source voltage. This allows the use of smaller

MOSFETs at the output.

During normal operation, the LTC4368 provides up to

13.1V of gate enhancement to the external back-to-back

N-channel MOSFETs. This turns on the MOSFETs, thus

connecting the load at VOUT to the supply at VIN.

GATE Drive

The LTC4368 turns on the external N-channel MOSFETs

by driving the GATE pin above VOUT. The voltage differ-

ence between the GATE and VOUT pins (gate drive) is a

function of VIN and VOUT.

Figure 3 highlights the dependence of the gate drive on

VIN and VOUT. When system power is first turned on

(SHDN low to high, SENSE = VOUT = 0V), gate drive is

at a maximum for all values of VIN. This helps prevent

startup problems into heavy loads by ensuring that there

is enough gate drive to support the load.

VIN

24V

PSMN4R8-100BSE

464k

1500k

121k

29.4k

RETRY

4368 F02

VOUT

FAULT

LTC4368-2

SENSE

0.22µF

VIN

SHDN

GATE

GND

+50mV

–3mV

VOUT

7V TO 36V

–0.75A TO 12.5A

0.004

2.2nF

INRUSH

CONTROL

22k

1200ms COOLDOWN

AFTER FORWARD

OC FAULT

OV = 36V

UV = 7V

SiR662

Figure 2. LTC4368-2 Protects Load from Voltage (–40V to 100V) and Current (–0.75A to 12.5A) Faults

Figure 3. Gate Drive (GATE – VOUT) vs VOUT

LTC2913 Datasheet(PDF) 10 Page - Analog Devices

LTC2913 Datasheet(HTML) 10 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Datasheet Download

Link URL