LT4363 pin FuncTionsENOUT: Open Collector Enable Output. The ENOUT pin goes below the threshold of 0.4V. Pull this pin above 2.1V or high impedance when the voltage at the OUT pin is within disconnect it to allow the internal current source to turn 0.5V of VCC and 3V above GND, indicating the external the part back on. The leakage current to ground at the MOSFET is fully on. The state of the pin is latched until the pin should be limited to no more than 1µA if no external OUT pin voltage drops below 2V, resetting the latch. The pull up is used to turn the part on. The SHDN pin can be internal NPN is capable of sinking up to 2mA of current. pulled up to 100V or below GND by 60V without damage. Exposed Pad (DFN Package Only): Exposed pad may be SNS: Current Sense Input. Connect this pin to the input of left open or connected to device ground (GND). the current sense resistor. The current limit circuit controls FB: Voltage Regulator Feedback Input. Connect this pin to the GATE pin to limit the sense voltage between SNS and the center tap of the resistive divider connected between OUT pins to 50mV. This is reduced to 25mV in a severe the OUT pin and ground. During an overvoltage condition, fault when OUT is below 2V. When in current limit mode, the GATE pin is controlled to maintain a 1.275V threshold a current source charges up the TMR pin. The voltage at the FB pin. Connect to GND to disable the OV clamp. difference with the OUT pin must be limited to less than 30V. Connect to OUT pin if unused. FLT: Open Collector Fault Output. This pin pulls low after the voltage at the TMR pin has reached the fault threshold TMR: Fault Timer Input. Connect a capacitor between this of 1.275V. It indicates the pass transistor is about to turn off pin and ground to set the times for early fault warning, because either the supply voltage has stayed at an elevated fault turn-off, and cool down periods. The current charg- level for an extended period of time (voltage fault) or the ing up this pin during fault conditions depends on the device is in an overcurrent condition (current fault). The voltage difference between the VCC and OUT pins. When internal NPN is capable of sinking up to 2mA of current. TMR reaches 1.275V, the FLT pin pulls low to indicate the detection of a fault condition. If the condition persists, the GATE: N-Channel MOSFET Gate Drive Output. The GATE pin pass transistor turns off when TMR reaches the threshold is pulled up by an internal charge pump current source to of 1.375V. A 2µA current source then continues to pull the 13V above the OUT pin. A 14V protection clamp limits this TMR up. When TMR reaches 4.3V, the 2µA current reverses voltage during faults. Both voltage and current amplifiers direction and starts to pull the TMR pin low. When TMR control the GATE pin to regulate the output voltage and reaches the retry threshold of 0.5V, the GATE pin pulls limit the current through the MOSFET. high turning back on the pass transistor for the LT4363-2 GND: Device Ground. version. The GATE pin latches low after fault time out for the LT4363-1. A minimum of 10nF capacitor is needed to OUT: Output Voltage Sense Input. This pin senses the compensate the loop. voltage at the source of the external N-channel MOSFET. The voltage difference between V UV: Undervoltage Comparator Input. When UV falls below CC and OUT sets the fault timer current. When this difference drops below 0.5V, the its threshold of 1.275V, the GATE is pulled down with a EN pin goes high impedance. 1mA current. When UV rises above 1.275V plus the hys- teresis, the pull down current disappears and the GATE OV (LT4363-2): Overvoltage Comparator Input. When OV pin is pulled up by the internal charge pump. If unused, is above its threshold of 1.275V, the fault retry function connect to V is inhibited even when the TMR pin voltage has reached CC. its retry threshold. As soon as the voltage at OV pin falls VCC: Positive Supply Voltage Input. The positive supply below its lower threshold the GATE pin is allowed to turn input ranges from 4V to 80V for normal operation. It can back on. Connect to GND if unused. also be pulled below ground by up to 60V during a reverse battery condition, without damaging the part. Shutting SHDN: Shutdown Control Input. The LT4363 can be down the LT4363 by pulling the SHDN pin to ground will shutdown to a low current mode by pulling the SHDN pin reduce the supply current to 7µA. 4363fb 8 For more information www.linear.com/LT4363 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts