LTC4411 datasheet(6/8 Pages) LINER

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LTC4411

4411fa

APPLICATIO S I FOR ATIO

INTRODUCTION

The LTC4411 is intended for power control applications

that include low loss diode ORing, fully automatic

switchover from a primary to an auxiliary source of power,

microcontroller controlled switchover from a primary to

an auxiliary source of power, load sharing between two or

more batteries, charging of multiple batteries from a

single charger and high side power switching.

Figure 4. State Transition Diagram

CONSTANT RON

REGULATION

CONSTANT ION

REGULATION

CONSTANT VON

REGULATION

REVERSE

BIASED

VIN – VOUT < VFWD

IOUT > IFWD IOUT < IFWD

IOUT > IMAX IOUT < IMAX

VIN – VOUT > VFWD

ISTAT = 0

DIODE ON

ISTAT = 10µA

DIODE OFF

ISTAT = 0

DIODE OFF

ISTAT = 0

DIODE OFF

ISTAT = 10µA

DIODE OFF

ISTAT = 0

DIODE ON

ISTAT = 0

DIODE ON

CONTROL

SHUTDOWN

UNDER

VOLTAGE

LOCK-OUT

OVER

TEMPERATURE

SHUTDOWN

TJ < 140°C

TJ > 150°C

VDD > 2.4

VDD < 2.3

VCTL < VIL

4411 F04

NORMAL OPERATION

VCTL > VIH

WHERE:

VDD = MAX {VIN, VOUT}

VIL = VTH – VHYST/2

VIH = VTH + VHYST/2

When the load current exceeds IMAX, an over current

condition is detected and the LTC4411 will limit the output

current. This will cause the output voltage to drop as the

load current exceeds the amount of current that the

LTC4411 can supply. This condition will increase the

power consumption within the LTC4411.

When an alternate power source is connected to the

output, the LTC4411 will sense the increased voltage at

OUT, and the amplifier (A) will increase the voltage at

VGATE. When VOUT is higher than VIN + VRTO, the internal

power source for the LTC4411 (VDD) will be diverted to

source current from the OUT pin. At the same time VGATE

will be pulled to VDD, which will turn off P1. The system is

now in the reverse turn-off mode. Power to the load is

being delivered from an alternate supply, and only a small

OPERATIO

current is drawn from IN to sense the potential VIN. During

reverse turn-off mode the STAT pin will sink 10µA to

indicate that the diode is not conducting.

When the CTL input is asserted (high), P1 will have its gate

voltage pulled high, and the STAT pin will sink 10µA. A 3µA

pull-down current on the CTL pin will ensure a low level at

this input if it is left open circuited.

The overtemperature condition is detected when the

internal die temperature increases beyond 150°C. The

overtemperature condition will cause the gate amplifier

(A) as well as P1 to be shut off. When the internal die

temperature cools to below 140°C, the amplifier will turn

on and revert to normal operation. Note that prolonged

operation under overtemperature conditions will degrade

reliability.

Automatic PowerPath Control

Figure 1 illustrates an application circuit for automatic

switchover of a load between a battery and a wall adapter

or other power input. With initial application of the battery,

the load will be charged up as the LTC4411 turns on. The

LTC4411 will control the gate voltage of its internal MOSFET

to reduce the MOSFET’s voltage drop to a low forward

voltage (VFWD). The system is now in the forward regula-

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