LTC4232
6
4232fc
For more information www.linear.com/LTC4232
pin FuncTions
FB: Foldback and Power Good Input. Connect this pin to
an external resistive divider from OUT. If the voltage falls
below 0.6V, the current limit is reduced using a foldback
profile (see the Typical Performance Characteristics sec
-
tion). If the voltage falls below 1.21V, the PG pin will pull
low to indicate the power is bad.
F
LT : 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.
I
MON
: 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 creates a
0V
to 2V voltage swing when current ranges from 0A to 5A.
INTV
CC
: Internal 3.1V Supply Decoupling Output. This pin
must have a 1µF or larger bypass capacitor. Overloading
this pin can disrupt internal operation.
I
SET
: 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 (R
ISET
) and an external resistor (R
SET
) between
I
SET
and ground create an attenuator that lowers the current
limit value. Due to circuit tolerance, R
SET
should not be
less than 2k. 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 I
SET
pin is made proportional to temperature
of the MOSFET switch.
OUT: Output of Internal MOSFET Switch. Connect this pin
directly to the load.
OV: Overvoltage Comparator Input. Connect this pin to an
external resistive divider from V
DD
. 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 cur
-
rent limit circuit controls the GATE pin to limit the sense
voltage
between the V
DD
and SENSE pins to 42mV (5.6A)
or less depending on the voltage at the FB pin. The exposed
pad on DHC 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 INTV
CC
for a fixed 2ms overcurrent delay
and 100ms auto-retry time.
UV
: Undervoltage Comparator Input. Ti
e high if unused.
Connect this pin to an external resistive divider from V
DD
.
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 F LT pin.
V
DD
: Supply Voltage and Current Sense Input. This pin
has an undervoltage lockout threshold of 2.73V.
