LT4363HMS-2#TRPBF IC

Technical Specifications of LT4363HMS-2#PBF

Datasheet	LT4363HMS-2#PBF datasheet
Product Photos	12-MSOP
Product Training Modules	Surge Stopper
Standard Package	37
Category	Circuit Protection
Family	Surge Suppression ICs
Series	–
Packaging	Tube
Voltage – Working	4 ~ 80V
Voltage – Clamping	Adjustable
Technology	Mixed Technology
Power (Watts)	–
Number of Circuits	1
Applications	Automotive
Package / Case	12-TSSOP (0.118″, 3.00mm Width)
Supplier Device Package	12-MSOP
Online Catalog	LT? 4363 Series
For Use With	DC1935A-A-ND – BOARD DEMO LT4363-1 DC1935A-B-ND – BOARD DEMO LT4363-2 DC2150A-C-ND – EVAL BOARD 28V 5A SURGE SUP DC2062A-A-ND – BOARD DEMO LT4363IDE-1 DC2062A-B-ND – BOARD DEMO LT4363IDE-2

LT4363HMS-2#TRPBF Description

The LT®4363 surge suppressor shields equipment from dangerous voltage spikes. Controlling the gate of an external N-channel MOSFET, limits output during overvoltage events like load dumps in cars. The output is capped at a safe level to keep the loads operational. The LT4363 safeguards against overcurrent faults by keeping an eye on the voltage drop between the SNS and OUT pins. The voltage across the current sense resistor is capped at 50mV by an onboard amplifier. A timer is initiated in either fault state, with the elapsed time rate proportionating to the stress placed on the MOSFET.

The FLT pin will draw low in advance whenever the timer is about to shut off. The MOSFET is disabled if the problem persists. The LT4363-1 won’t start up again until manually reset, but the LT4363-2 can be used again after being let to cool down. Overvoltage (OV) and Undervoltage (UV) are detected and prevented thanks to two precision comparators. This is because the external MOSFET is turned off when the voltage falls below the UV threshold. The MOSFET is disabled if the input supply voltage rises above the OV threshold. Instead of using a Schottky diode for reverse input protection, back-to-back MOSFETs can be utilized to reduce voltage drop and power loss. As a result of a shutdown pin, the quiescent current drops to below 7A when the device is powered down.

LT4363HMS-2#TRPBF Features

• Withstands Over 100V Surges using a VCC Clamp.
• 4V to 80V is a large operating voltage range.
• Voltage Adjustable Output Clamp.
• Limit for fast overcurrent: less than 5 s.
• Reverse input security set at -60V.
• Adjustable thresholds for the UV/OV comparator.
• Low Shutdown Current of 7 A.
• The shutdown Pin Can Handle Voltages of -60 to 100V.
• Fault Timer Adjustment.
• Regulates an N-Channel MOSFET.
• Retry Duty Cycle During Faults of Less Than 1%, LT4363-2
• obtainable in 16-Pin SO Packages, 12-Pin MSOP, and 12-Pin (4mm 3mm) DFN packages.

LT4363HMS-2#TRPBF Applications

• Industrial/Avionic/Automotive Surge Protection
• Live Insertion/Hot SwapTM.
• High Side Switch for Systems Using Batteries.
• Apps for intrinsic safety.

Applications Information

In the event of an output overload or supply transient, the LT4363 reduces the voltage and current supplied to the load. While the output will remain on during failures of shorter duration, the output will be disabled during faults of longer duration to safeguard the MOSFET pass device. Under normal conditions, the MOSFET functions as a low-impedance channel from the input to the load, while under fault conditions, it takes on the role of a series regulator.

● Overvoltage Fault

If the input voltage is too high, the output voltage will not go too high, thanks to the LT4363. The FB pin’s voltage is kept at 1.275V thanks to an integrated amplifier that controls the GATE pin. The MOSFET provides current to the load during this time. Because of this, operations can continue normally, even during brief periods of overvoltage. The MOSFET will shut off with the timer if the overvoltage persists.

● Overcurrent Fault

Regarding protecting against output short circuits or high load current, the LT4363 has you covered with its adjustable current limit. In an overcurrent condition, the GATE pin is regulated to maintain a 50mV threshold for the voltage sensed between the SNS and OUT pins. If the output is severely shorted and OUT is less than 2V, the current sense voltage is dropped to 25mV to reduce power consumption in the MOSFET further. The timer cuts power to the MOSFET if the overcurrent condition persists.

● Fault Timer Overview

An adjustable timer limits the duration of overvoltage and overcurrent circumstances. A capacitor connected to the TMR pin controls the delay in reporting a fault condition at the FLT pin and the total delay before the MOSFET is shut off. The delay until the MOSFET is allowed to switch back on is likewise controlled by this capacitor. An external current source charges the TMR pin capacitor in the event of an overvoltage or overcurrent fault condition. The exact current level varies depending on the fault type and the VDS voltage drop across the MOSFET.

Instead of wasting the MOSFET’s Safe Operating Area (SOA) with a constant timer current, this method maximizes its potential. In typical operation, the TMR pin is biased to 0.5V. A fault triggers the timer to charge to 1.275V and commences its early warning phase. When the timer reaches 1.375V, the MOSFET is turned off by pulling the FLT pin low. FLT low indicates a warning phase, during which the load has time to do maintenance, such as saving data, in preparation for an imminent power outage.

The timer goes into the cool down phase after a fault. The LT4363-1 stays off until reset, but the LT4363-2 starts up on its own after the cool down period ends. If the OV pin is higher than 1.275V, the LT4363-2 will not attempt a retry. In the event of a prolonged input overvoltage scenario, motorboating is therefore prevented.

● Intermittent Fault Conditions

The timer stops working briefly whenever there is an overvoltage or overcurrent problem. When the input voltage drops below the regulation value or the current limit is exceeded, the timer capacitor is discharged to 0.5V using a 2 A current sink if the TMR pin has not yet reached 1.275V. With a TMR voltage above 1.275V, FLT is turned down. If the overvoltage or overcurrent is reduced before the timer capacitor reaches 1.375V, the capacitor will discharge with 2A to 0.5V, resetting FLT to its high state. The timer capacitor will integrate the charging and discharging currents if a series of brief overvoltage or overcurrent events occurs in fast succession.

● MOSFET Selection

The load current is conducted through an N-channel MOSFET driven by the LT4363. The MOSFET’s on-resistance RDS(ON), maximum drain-source voltage V(BR)DSS, threshold voltage, and source-to-gate offset angle (SOA) are all noteworthy properties. There should be a difference between the supply and maximum drain-source voltage. The supply voltage will appear across the MOSFET if the output is shorted to ground or an overvoltage event occurs. For systems with VCC greater than 9V, the MOSFET gate drive is assured to be over 10 and less than 16 volts.

Because of this, regular N-channel MOSFETs can be used. Since the gate drive might be as low as 4.5V, a logic level MOSFET is needed for systems with VCC less than 9V. All possible fault states must be accounted for in the MOSFET’s SOA. The pass transistor is activated and uses almost no power when functioning normally. However, in cases of excessive output voltage or MOSFET current, the GATE pin is used to restore normal operation. In such circumstances, the MOSFET can withstand a large current and a high voltage drop. When choosing the fault timer capacitor, it is important to consider the SOA curves of the MOSFET.

Conclusion

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