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LTC4217CDHC-12-TRPBF Datasheet(PDF) 7 Page - Linear Technology |
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LTC4217CDHC-12-TRPBF Datasheet(HTML) 7 Page - Linear Technology |
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7 / 18 page  LTC4217 7 4217fc PIN FUNCTIONS FB: Foldback and Power Good Input. Connect this pin to an external resistive divider from OUT for the LTC4217 (adjust- able) version. The LTC4217-12 version uses a fixed internal divider with optional external adjustment. Open the pin if the LTC4217-12 thresholds for 12V operation are desired. If the voltage falls below 0.6V, the current limit is reduced using a foldback profile (see the Typical Performance Characteristics section). If the voltage falls below 1.21V, the PG pin will pull low to indicate the power is bad. FLT: Overcurrent Fault Indicator. Open-drain output pulls low when an overcurrent fault has occurred and the circuit breaker trips. For overcurrent auto-retry tie to UV pin (see the Applications Information section for details). GATE: Gate Drive for Internal N-channel MOSFET. An internal 24μA current source charges the gate of the N-channel MOSFET. At start-up the GATE pin ramps up at a 0.3V/ms rate determined by internal circuitry. During an undervoltage or overvoltage condition a 250μA pull-down current turns the MOSFET off. During a short-circuit or undervoltage lockout condition, a 140mA pull-down cur- rent source between GATE and OUT is activated. GND: Device Ground. IMON: Current Monitor Output. The current in the internal MOSFET switch is divided by 20,000 and sourced from this pin. Placing a 20k resistor from this pin to GND creates a 0V to 2V voltage swing when current ranges from 0A to 2A. INTVCC: Internal 3V Supply Decoupling Output. This pin must have a 0.1μF or larger bypass capacitor. ISET: Current Limit Adjustment Pin. For a 2A current limit value open this pin. This pin is driven by a 20k resistor in series with a voltage source. The pin voltage is used to generatethecurrentlimitthreshold.Theinternal20kresistor and an external resistor between ISET and ground create an attenuator that lowers the current limit value. In order to match the temperature variation of the sense resistor, the voltage on this pin increases at the same rate as the sense resistance increases. Therefore the voltage at ISET pin is proportional to temperature of the MOSFET switch. OUT: Output of Internal MOSFET Switch. Connect this pin directly to the load. In the LTC4217-12 version, the PG comparator monitors an internal resistive divider between the OUT pin and GND. OV: Overvoltage Comparator Input. Connect this pin to an external resistive divider from VDD for the LTC4217 (adjust- able) version. The LTC4217-12 version uses a fixed internal divider with optional external adjustment for 12V operation. Open the pin if the LTC4217-12 thresholds are desired. If the voltage at this pin rises above 1.235V, an overvoltage is detected and the switch turns off. Tie to GND if unused. PG: Power Good Indicator. Open-drain output pulls low when the FB pin drops below 1.21V indicating the power is bad. If the FB pin rises above 1.23V and the GATE to OUT voltage exceeds 4.2V, the open-drain pull-down releases the PG pin to go high. SENSE: Current Sense Node and MOSFET Drain. The current limit circuit controls the GATE pin to limit the sense voltage between the VDD and SENSE pins to 15mV (2A) or less depending on the voltage at the FB pin. The exposed pad on DHC and FE packages are connected to SENSE and must be soldered to an electrically isolated printed circuit board trace to properly transfer the heat out of the package. TIMER: Timer Input. Connect a capacitor between this pin and ground to set a 12ms/μF duration for current limit before the switch is turned off. If the UV pin is toggled low while the MOSFET switch is off, the switch will turn on again following a cooldown time of 518ms/μF duration. Tie this pin to INTVCC for a fixed 2ms overcurrent delay and 100ms auto-retry time. UV: Undervoltage Comparator Input. Tie high if unused. Connect this pin to an external resistive divider from VDDfor the LTC4217 (adjustable) version. The LTC4217-12 version drives the UV pin with an internal resistive divider from VDD. Open the pin if the preset LTC4217-12 thresholds for 12V operation are desired. If the UV pin voltage falls below 1.15V, an undervoltage is detected and the switch turns off. Pulling this pin below 0.62V resets the overcurrent fault and allows the switch to turn back on (see the Applications Information section for details). If overcurrent auto-retry is desired then tie this pin to the FLT pin. VDD: Supply Voltage and Current Sense Input. This pin has an undervoltage lockout threshold of 2.73V. |
Similar Part No. - LTC4217CDHC-12-TRPBF |
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Similar Description - LTC4217CDHC-12-TRPBF |
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