LTC4213 datasheet(18/22 Pages) AD

18 / 22 page

LTC4213

Rev. A

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APPLICATIONS INFORMATION

activates and the GATE pin pulls down and turns off the

external MOSFET.

Typical Electronic Fuse Application for a Single

Supply System

Figure 6 shows a single supply electronic fuse applica-

tion. An RC filter at VCC pin filters out transient spikes.

An optional Schottky diode can be added if severe VCC

dips during a fault start-up condition is a concern. The

use of the Schottky and RC filter combination is allowed

if the load supply is above 2.9V and the total voltage drop

towards the VCC pin is less than 0.4V. The LTC4213’s

internal UVLO filter further rejects bias supply’s transients

of less than tRESET. During power-up, it is good engineer-

ing practice to ensure that VCC is fully established before

the ON pin enables the system at VON = 0.8V. In this appli-

cation, the VCC voltage reached final value approximately

after a 5.3 • R1 C1 delay. This is followed by the ON pin

exceeding 0.8V after a 0.17 • R2C2 delay. The GATE pin

starts up after an internal tDEBOUNCE delay.

Typical Single Supply Hot Swap Application

A typical single supply hot swap application is shown in

Figure 7. The RESET signal at the backplane is held low

initially. When the PCB long edge makes contact the ON

pin is held low (<0.4V) and the LTC4213 is kept in reset

mode. When the short edge makes contact the VIN load

supply is connected to the card. The VCC is biased via

the RC filter. The VOUT is pre-charged via R5. To pow-

er-up successfully, the R5 resistor value should be small

enough to provide the load requirement and to overcome

the 280µA current source sinking into the SENSEN pin.

On the other hand, the R5 resistor value should be big

enough avoiding big inrush current and preventing big

short circuit current. When RESET signals high at back-

plane, C2 capacitor at the ON pin charges up via the R3/

R2 resistive divider. When ON pin voltage exceeds 0.8V,

the GATE pin begins to ramp up. When the GATE voltage

peaks, the external MOSFET is fully turned on and the

VIN-to-VOUT voltage drop reduces. In normal mode oper-

ation, the LTC4213 monitors the load current through the

RDS(ON) of the external MOSFET.

Figure 6. Single Supply Electronic Fuse

4213 F06

LTC4213

VCC

READY

10F

CLOAD

100F

10k

ISEL

GND

GATE

SI4410DY

2N7002

VIN

VOUT

SENSEN

SENSEP

CIN

100F

33Ω

MBRO520L

324k

80.6k

RESET

VIN

0.22F

LTC4213 Datasheet(PDF) 18 Page - Analog Devices

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