LTC4242
8
4242f
PI FU CTIO S
UUU
12V
GATE1
/12V
GATE2
: Gate Drive for 12V Supply External
N-Channel MOSFET. An internal charge pump provides
a 9µA pull-up current to ramp up 12V
GATEn
. During turn
off, a 1mA pull-down current source discharges 12V
GATEn
to ground. 12V
GATEn
is internally clamped to 5.5V above
12V
OUTn
. During an overcurrent fault, a 250mA pull-down
current source between 12V
GATEn
and 12V
OUTn
is activated.
An external RC network is required at the pin for optimum
current limit response.
12V
SENSE1
/12V
SENSE2
: 12V Supply Current Limit Sense
Input. A sense resistor is placed in the supply path between
12V
INn
and 12V
SENSEn
to sense the 12V channel’s load
current. The voltage across the sense resistor is monitored
for active current limit and circuit breaker fault detection.
To disable the circuit breaker function for the 12V channel,
connect 12V
SENSEn
to 12V
INn
.
12V
IN1
/12V
IN2
: 12V Supply Input. An undervoltage lockout
circuit disables the 12V and 3.3V supplies when 12V
INn
voltage is less than 9.78V.
12V
OUT1
/12V
OUT2
: 12V Output Connection. Connect this
pin to the source of the 12V supply external N-channel
MOSFET for gate drive return. PGOOD1/PGOOD2 cannot
pull low until this pin goes above 10.38V. A 700Ω active
pull-down discharges 12V
OUTn
to ground when the external
MOSFET is turned off.
3V
GATE1
/3V
GATE2
: Gate Drive for 3.3V Supply External
N-Channel MOSFET. An internal charge pump provides
a 9µA pull-up current to ramp up 3V
GATEn
. During turn
off, a 1mA pull-down current source discharges 3V
GATEn
to ground. 3V
GATEn
is internally clamped to 5.5V above
3V
OUTn
. During an overcurrent fault, a 250mA pull-down
current source between 3V
GATEn
and 3V
OUTn
is activated.
An external RC network is required at the pin for optimum
current limit response.
3V
SENSE1
/3V
SENSE2
: 3.3V Supply Current Limit Sense Input.
A sense resistor is placed in the supply path between 3V
INn
and 3V
SENSEn
to sense 3.3V channel’s load current. The
voltage across the sense resistor is monitored for active
current limit and circuit breaker fault detection. To disable
the circuit breaker function for the 3.3V channel, connect
3V
SENSEn
to 3V
INn
.
3V
IN1
/3V
IN2
: 3.3V Supply Input. An undervoltage lockout
circuit disables the 3.3V and 12V supplies when 3V
INn
voltage is less than 2.67V.
3V
OUT1
/3V
OUT2
: 3.3V Output Connection. Connect this
pin to the source of the 3.3V supply external N-channel
MOSFET for gate drive return. PGOOD1/PGOOD2 cannot
pull low until this pin goes above 2.855V. A 375Ω active
pull-down discharges 3V
OUTn
to ground when the external
MOSFET is turned off.
AUXFAULT1/AUXFAULT2: AUX Supply Fault Status Out-
put. AUXFAULTn is normally pulled high by an internal 9µA
pull-up. It asserts low if the AUX channel shuts off due
to an overcurrent fault or due to the device temperature
rising above 150°C. Indicates switch ON status when
FONn and ENn are high.
AUXON1/AUXON2: AUX Supply On Control Input. A rising
edge turns on the internal FET, while a falling edge turns it
off. Pulling this pin below 0.6V for more than 3.5µs clears
the fault on the AUX channel.
AUXIN1/AUXIN2: AUX Supply Input. An undervoltage
lockout circuit disables the AUX supply when the voltage
at AUXINn is less than 2.67V. AUXINn is the input to the
internal pass FET.
AUXOUT1/AUXOUT2: AUX Supply Output. AUXOUTn
is the output from the internal pass FET. AUXPGOOD1/
AUXPGOOD2 cannot pull low until this pin goes above
2.855V. A 750Ω active pull-down discharges AUXOUTn
to ground when the internal FET is turned off.
