LTC4219 datasheet(7/16 Pages) LINER

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LTC4219

4219f

PIN FUNCTIONS

EN1: Inverted Enable 1 Input. Ground this pin to enable

the MOSFET to turn on after 100ms debounce delay. If

the voltage at this pin rises above 1.235V for longer than

10μs a turn-off command is detected, the overcurrent

fault is cleared and the MOSFET gate is discharged with

a 250μA current. Bringing this pin below 1.15V and EN2

low for 100ms begins GATE pin ramping.

EN2: Inverted Enable 2 Input. Ground this pin to enable

the MOSFET to turn on after 100ms debounce delay. If

the voltage at this pin rises above 1.235V for longer than

10μs a turn-off command is detected and the MOSFET

gate is discharged with a 250μA current. Bringing this

pin below 1.15V and EN1 low for 100ms begins GATE

pin ramping.

Exposed Pad: SENSE.

FB: Foldback and Power Good Input. The FB pin is driven

from an internal resistive divider from OUT for both the

LTC4219-12 and LTC4219-5. These versions preset 12V

and 5V foldback and power good levels. If the OUT volt-

age falls below 2.5V (LTC4219-5) or 6V (LTC4219-12)

the current limit is reduced using a foldback proﬁle (see

the Typical Performance Characteristics section). If the

FB voltage falls below 1.21V the PG pin will pull high 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.

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 50,000 and sourced from

this pin. Placing a 20k resistor from this pin to GND cre-

ates a 0V to 2V voltage swing when current ranges from

0A to 5A.

INTVCC: Internal 3V Supply Decoupling Output. This pin

must have a 0.1μF or larger bypass capacitor.

ISET: Current Limit Adjustment Pin. For a 5.6A 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 generate the current limit threshold. The internal 20k

resistor 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. An internal resistive divider is con-

nected to this pin to drive the FB pin.

PG: Power Good Indicator. Open-drain output releases

the PG pin to go high 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

output pulls low indicating power is good.

SENSE: Current Sense Node and MOSFET Drain. The cur-

rent limit circuit controls the GATE pin to limit the sense

voltage between the VDD and SENSE pins to 42mV (5.6A)

or less depending on the voltage at the FB pin. The exposed

pad on the DHC package is 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 EN1 pin is toggled

ﬁrst high then 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.

VDD: Supply Voltage and Current Sense Input. This pin

has an undervoltage lockout threshold of 2.73V.

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