LTC4213IDDB datasheet(18/20 Pages) LINER

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LTC4213

4213f

APPLICATIO S I FOR ATIO

4213 F06

LTC4213

VCC

READY

10µF

CLOAD

100µF

10k

ISEL

GND

GATE

SI4410DY

2N7002

VIN

VOUT

SENSEN

SENSEP

CIN

100µF

33Ω

MBRO520L

324k

80.6k

RESET

VIN

0.22µF

Figure 6. Single Supply Electronic Fuse

SENSEP exceeds VCC + 0.7V for more than 65µs, the

LTC4213’s internal overvoltage protection circuit acti-

vates 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 application.

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

application, the VCC voltage reached final value approxi-

mately 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.

Hot Swap is a trademark of Linear Technology Corporation.

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 power-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 backplane, 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 operation, the

LTC4213 monitors the load current through the RDSON of

the external MOSFET.

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