Datasheet LTC4368 (Analog Devices) - 9

link to page 9 LTC4368
OPERATION
Many of today’s electronic systems get their power from of a single catastrophic event, or over time as devices external sources such as wall adapters, batteries and cus- degrade from repeated overstress. tom power supplies. Figure 1 shows a supply arrange- The LTC4368 limits these errant overvoltage and overcur- ment using a DC barrel connector. Power is supplied by rent conditions and helps extend the life of the electronic an AC adapter or, if the plug is withdrawn, by a removable systems it protects. When the part detects an overcurrent battery. Note that the polarity of the AC adapter and barrel or overvoltage fault, it isolates the input supply from the connector varies by manufacturer. Trouble arises when load by turning off the external back-to-back MOSFETs. any of the following occurs: The LTC4368 provides accurate overvoltage and under- • The battery is installed backwards voltage comparators to ensure that power is applied to • A wall adapter of opposite polarity is attached the load only if the input supply meets the user selectable • A wall adapter of excessive voltage is attached voltage window. Additionally, two accurate overcurrent comparators disconnect the load from the supply when • A wall adapter with an AC output is attached excessive current flows in either the forward (+50mV/ • The battery is discharged below a safe level RSENSE) or reverse (–50mV or –3mV/RSENSE) direction. Reverse supply voltage protection circuits automatically • The load or the input is shorted to ground or to isolate the load from negative input voltages. During nor- another supply mal operation, a high voltage charge pump enhances the • Excessive current flows from the supply to the load gate of dual external N-channel power MOSFETs, thus or from the load to the supply providing a low loss path for qualified power. Power con- sumption is 5µA during shutdown and 80µA while operat- These conditions, if unchecked, can damage electronic ing. The LTC4368 integrates all these functions in small systems and their connectors. Damage can take the form 10-lead 3mm × 3mm DFN and MSOP packages. BI-DIRECTIONAL OVERCURRENT PROTECTION –40V TO 100V PROTECTION RANGE +50mV M1 M2
+
2.5V TO 60V INRUSH OPERATING RANGE CONTROL –3mV AC BATTERY LOAD RGATE ADAPTER CIRCUIT INPUT CGATE
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GATE SENSE V V OUT IN R4 SHDN OV, UV PROTECTION R3 LTC4368-2 THRESHOLDS SET TO UV FAULT SATISFY LOAD CIRCUIT R2 OV RETRY R1 GND CRETRY 4368 F01
Figure 1. Polarity Protection for DC Barrel Connectors
Rev A For more information www.analog.com 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Pin Functions Block Diagram Applications Information Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts