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LTC4355 Datasheet(PDF) 8 Page - Linear Technology |
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LTC4355 Datasheet(HTML) 8 Page - Linear Technology |
8 / 24 page LT4363 8 4363fa PIN FUNCTIONS ENOUT:OpenCollectorEnableOutput.TheENOUTpingoes high impedance when the voltage at the OUT pin is within 0.5V of VCC and 3V above GND, indicating the external MOSFET is fully on. The state of the pin is latched until the OUT pin voltage drops below 2V, resetting the latch. The internal NPN is capable of sinking up to 2mA of current. Exposed Pad (DFN Package Only): Exposed pad may be left open or connected to device ground (GND). FB: Voltage Regulator Feedback Input. Connect this pin to the center tap of the resistive divider connected between the OUT pin and ground. During an overvoltage condition, the GATE pin is controlled to maintain a 1.275V threshold at the FB pin. Connect to GND to disable the OV clamp. FLT: Open Collector Fault Output. This pin pulls low after the voltage at the TMR pin has reached the fault threshold of1.275V.Itindicatesthepasstransistorisabouttoturnoff becauseeitherthesupplyvoltagehasstayedatanelevated level for an extended period of time (voltage fault) or the device is in an overcurrent condition (current fault). The internal NPN is capable of sinking up to 2mA of current. GATE:N-ChannelMOSFETGateDriveOutput.TheGATEpin is pulled up by an internal charge pump current source and clamped to 14V above the OUT pin. Both voltage and cur- rent amplifiers control the GATE pin to regulate the output voltage and limit the current through the MOSFET. GND: Device Ground. OUT: Output Voltage Sense Input. This pin senses the voltage at the source of the external N-channel MOSFET. The voltage difference between VCC and OUT sets the fault timer current. When this difference drops below 0.5V, the EN pin goes high impedance. OV (LT4363-2): Overvoltage Comparator Input. When OV is above its threshold of 1.275V, the fault retry function is inhibited even when the TMR pin voltage has reached its retry threshold. As soon as the voltage at OV pin falls below its lower threshold the GATE pin is allowed to turn back on. Connect to GND if unused. SHDN: Shutdown Control Input. The LT4363 can be shutdown to a low current mode by pulling the SHDN pin below the threshold of 0.4V. Pull this pin above 2.1V or disconnect it to allow the internal current source to turn the part back on. The leakage current to ground at the pin should be limited to no more than 1µA if no external pull up is used to turn the part on. The SHDN pin can be pulled up to 100V or below GND by 60V without damage. SNS: Current Sense Input. Connect this pin to the input of thecurrentsenseresistor.Thecurrentlimitcircuitcontrols the GATE pin to limit the sense voltage between SNS and OUT pins to 50mV. This is reduced to 25mV in a severe fault when OUT is below 2V. When in current limit mode, a current source charges up the TMR pin. The voltage difference with the OUT pin must be limited to less than 30V. Connect to OUT pin if unused. TMR: Fault Timer Input. Connect a capacitor between this pin and ground to set the times for early fault warning, fault turn-off, and cool down periods. The current charg- ing up this pin during fault conditions depends on the voltage difference between the VCC and OUT pins. When TMR reaches 1.275V, the FLT pin pulls low to indicate the detection of a fault condition. If the condition persists, the pass transistor turns off when TMR reaches the threshold of 1.375V. A 2µA current source then continues to pull the TMR up. When TMR reaches 4.3V, the 2µA current reverses direction and starts to pull the TMR pin low. When TMR reaches the retry threshold of 0.5V, the GATE pin pulls high turning back on the pass transistor for the LT4363-2 version. The GATE pin latches low after fault time out for the LT4363-1. UV: Undervoltage Comparator Input. When UV falls below its threshold of 1.275V, the GATE is pulled down with a 1mA current. When UV rises above 1.275V plus the hys- teresis, the pull down current disappears and the GATE pin is pulled up by the internal charge pump. If unused, connect to VCC. VCC: Positive Supply Voltage Input. The positive supply input ranges from 4V to 80V for normal operation. It can also be pulled below ground by up to 60V during a reverse battery condition, without damaging the part. Shutting down the LT4363 by pulling the SHDN pin to ground will reduce the supply current to 7µA. |
Similar Part No. - LTC4355 |
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Similar Description - LTC4355 |
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