LTC4223-1/LTC4223-2
7
422312f
PIN FUNCTIONS
12V
SENSE
(Pin 1): 12V Current Sense Input. Connect this
pin to the output of the current sense resistor. The electronic
circuit breaker trips if the voltage across the sense resistor
exceeds 50mV for more than a fault fi lter delay.
12V
IN
(Pin 2): 12V Supply Input. Undervoltage lockout
disables the 12V supply until the input at 12V
IN
exceeds
9.7V.
12IMON (Pin 3): 12V Current Sense Monitoring Output.
This pin monitors the sense voltage between 12V
IN
and
12V
SENSE
. The gain ratio between this pin’s voltage and
the sense voltage is 33.
12ON (Pin 4): 12V Supply On Control Digital Input. A ris-
ing edge turns on the external N-channel MOSFET if
⎯
E
⎯
N
is pulled low and a falling edge turns it off. A high-to-low
transition on this pin will clear the 12V supply faults.
AUXIN (Pin 5): Auxiliary Supply Input. An internal 0.3Ω
switch is connected between AUXIN and AUXOUT pins.
Undervoltage lockout holds the switch off until the input
at AUXIN exceeds 2.5V.
V
CC
(Pin 6): Bias Supply Input. This pin provides power
to the device’s internal circuitry and operates from 2.7V to
6V. Undervoltage lockout circuit disables the device until
the input at V
CC
exceeds 2.45V. Bypass with 330nF.
AUXON (Pin 7): Auxiliary Supply On Control Digital Input.
A rising edge turns on the internal switch if
⎯
E
⎯
N is pulled
low and a falling edge turns it off. A high-to-low transi-
tion on both this pin and 12ON pin will clear the auxiliary
supply faults.
GND (Pin 8): Device Ground.
TIMER (Pin 9): Timer Capacitor Terminal. Connect a
capacitor between this pin and ground to set a 741ms/μF
duration for initial timing cycle, 123ms/μF for AUX current
limit during power-up and 6ms/μF duration for 12V current
limit before the external MOSFET is turned off.
⎯
E
⎯
N (Pin 10): Enable Input Intended for Card Presence
Detect. Ground this pin to enable the external N-channel
MOSFET and internal switch to turn on. If this pin is pulled
high, the switches are not allowed to turn on. An internal
100k resistor pulls up this pin. A high-to-low transition
will clear faults.
⎯
A
⎯
U
⎯
X
⎯
P
⎯
G
⎯
O
⎯
O
⎯
D (Pin 11): Auxiliary Supply Power Status
Output. Open drain output that is normally pulled high
by an internal 10μA current source or an external pull-up
resistor to V
CC
. It pulls low when the AUXOUT pin voltage
exceeds the power-good threshold of 2.901V.
AUXOUT (Pin 12): Auxiliary Supply Output. This pin is
the output from the internal switch connected between
AUXIN and AUXOUT pins. It signals
⎯
A
⎯
U
⎯
X
⎯
P
⎯
G
⎯
O
⎯
O
⎯
D low when
it exceeds 2.901V. A 750Ω active pull-down discharges
AUXOUT to ground when the internal switch is turned
off.
⎯
F
⎯
A
⎯
U
⎯
L
⎯
T (Pin 13): Auxiliary and 12V Supply Fault Status
Output. Open drain output that is normally pulled high by an
internal 10μA current source or an external pull-up resistor
to V
CC
. It pulls low when the circuit breaker is tripped due
to an overcurrent fault on auxiliary or 12V supply.
⎯
1
⎯
2
⎯
P
⎯
G
⎯
O
⎯
O
⎯
D (Pin 14): 12V Supply Power Status Output.
Open drain output that is normally pulled high by an in-
ternal 10μA current source or an external pull-up resistor
to V
CC
. It pulls low when the 12V
OUT
pin voltage exceeds
the power-good threshold of 10.36V.
12V
OUT
(Pin 15): 12V Gate Drive Return and Power-Good
Input. Connect this pin to the source of the external N-
channel MOSFET for gate drive return. This pin signals
⎯
1
⎯
2
⎯
P
⎯
G
⎯
O
⎯
O
⎯
D low when it exceeds 10.36V. When the external
MOSFET is turned off, 12V
OUT
is discharged to ground
through a 800Ω active pull-down.
12V
GATE
(Pin 16): Gate Drive for 12V Supply External N-
Channel MOSFET. An internal 10μA current source charges
the gate of the external N-channel MOSFET. An internal
clamp limits the gate voltage to 6.2V above 12V
OUT
. A
resistor and capacitor network from this pin to ground
sets the turn-on rate and compensates the active current
limit. During turn-off, a 1mA pull-down current discharges
12V
GATE
to ground. During short circuit or undervoltage
lockout, a 160mA pull-down current between 12V
GATE
and
12V
OUT
is activated.
Exposed Pad (Pin 17, DHD Package): Exposed pad may
be left open or connected to device ground.
