LTC2913 datasheet(9/22 Pages) AD

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LTC4368

Rev. B

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OPERATION

Many of today’s electronic systems get their power from

external sources such as wall adapters, batteries and cus-

tom power supplies. Figure 1 shows a supply arrange-

ment using a DC barrel connector. Power is supplied by

an AC adapter or, if the plug is withdrawn, by a removable

battery. Note that the polarity of the AC adapter and barrel

connector varies by manufacturer. Trouble arises when

any of the following occurs:

• The battery is installed backwards

• A wall adapter of opposite polarity is attached

• A wall adapter of excessive voltage is attached

• A wall adapter with an AC output is attached

• The battery is discharged below a safe level

• The load or the input is shorted to ground or to

another supply

• Excessive current flows from the supply to the load

or from the load to the supply

These conditions, if unchecked, can damage electronic

systems and their connectors. Damage can take the form

Figure 1. Polarity Protection for DC Barrel Connectors

of a single catastrophic event, or over time as devices

degrade from repeated overstress.

The LTC4368 limits these errant overvoltage and overcur-

rent conditions and helps extend the life of the electronic

systems it protects. When the part detects an overcurrent

or overvoltage fault, it isolates the input supply from the

load by turning off the external back-to-back MOSFETs.

The LTC4368 provides accurate overvoltage and under-

voltage comparators to ensure that power is applied to

the load only if the input supply meets the user selectable

voltage window. Additionally, two accurate overcurrent

comparators disconnect the load from the supply when

excessive current flows in either the forward (+50mV/

RSENSE) or reverse (–50mV or –3mV/RSENSE) direction.

Reverse supply voltage protection circuits automatically

isolate the load from negative input voltages. During nor-

mal operation, a high voltage charge pump enhances the

gate of dual external N-channel power MOSFETs, thus

providing a low loss path for qualified power. Power con-

sumption is 5µA during shutdown and 80µA while operat-

ing. The LTC4368 integrates all these functions in small

10-lead 3mm × 3mm DFN and MSOP packages.

+50mV

–3mV

BATTERY

–40V TO 100V PROTECTION RANGE

ADAPTER

INPUT

OV, UV PROTECTION

THRESHOLDS SET TO

SATISFY LOAD CIRCUIT

–

2.5V TO 60V

OPERATING RANGE

LOAD

CIRCUIT

VIN

RETRY

SHDN

4368 F01

VOUT

FAULT

GATE

BI-DIRECTIONAL

OVERCURRENT PROTECTION

GND

LTC4368-2

CGATE

SENSE

INRUSH

CONTROL

RGATE

CRETRY

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