LTC4365

8

4365f

OPERATION

Many of today’s electronic systems get their power from

external sources such as a wall wart adapter, batteries

and custom power supplies. These power sources are

often unreliable, wired incorrectly, out of spec, or just

plain wrong. This can lead to supply voltages that are too

high, too low, or even negative. If these power sources

are applied directly to the electronic systems, the systems

could be subject to damage. The LTC4365 is an input

voltage fault protection N-channel MOSFET controller.

The part isolates an input supply from its load to protect

the load from unexpected supply voltage conditions, while

providing a low loss path for qualified power.

To protect electronic systems from improperly connected

power supplies, system designers will often add discrete

diodes, transistors and high voltage comparators. The

high voltage comparators enable system power only if

the input supply falls within a desired voltage window.

A Schottky diode or P-channel MOSFET typically added

in series with the supply protects against reverse supply

connections.

The LTC4365 provides accurate overvoltage and

undervoltage comparators to ensure that power is ap-

plied to the system only if the input supply meets the user

selectable voltage window. Reverse supply protection

circuits automatically isolate the load from negative input

voltages. During normal operation, a high voltage charge

pump enhances the gate of external N-channel power

MOSFETs. Power consumption is 10μA during shutdown

and 125μA while operating. The LTC4365 integrates all

these functions in tiny TSOT-23 and 3mm × 2mm DFN

packages.

APPLICATIONS INFORMATION

The LTC4365 is an N-channel MOSFET controller that

protects a load from faulty supply connections. A basic

application circuit using the LTC4365 is shown in Figure 1.

UV

OV

SHDN

OV = 18V

UV = 3.5V

4365 F01

FAULT

GATE

12V NOMINAL

3.5V TO 18V

SI4946

60V DUAL

GND

LTC4365

R5

100k

100μF

R3

1820k

R2

243k

R1

59k

+

M1

M2

Figure 1. LTC4365 Protects Load from –40V to

prevented from getting to the load and can be as high as

60V and as low as –40V. The circuit of Figure 1 protects

ternal components are needed.

During normal operation, the LTC4365 provides up to

9.8V of gate enhancement to the external back-to-back

N-channel MOSFETs. This turns on the MOSFET, thus

GATE Drive

The LTC4365 turns on the external N-channel MOSFETs