LTC4245
9
4245fa
PI FU CTIO S
UUU
12V
GATE
: Gate Drive for 12V Supply External N-Channel
MOSFET. An internal 20μA current source charges the gate
of the external N-channel MOSFET. An internal clamp limits
the gate voltage to 6.2V above 12V
OUT
. During turn-off a
1.3mA pull-down current discharges 12V
GATE
to ground.
During short-circuit a 250mA pull-down current between
12V
GATE
and 12V
OUT
is activated.
12V
IN
: 12V Supply, Current Sense and ADC Input. The
internal low voltage supply V
CC
is generated from 12V
IN
.
An undervoltage lockout circuit, with 38mV hysteresis,
prevents any external MOSFET from turning on when this
pin is below 10.5V.
12V
OUT
: 12V Gate Drive Return; Foldback, ADC and Power
Bad Input. Connect this pin to the source of the 12V supply
external N-channel MOSFET switch for gate drive return.
Power is considered bad if this pin drops below 11.1V. The
comparator on this pin has a built-in hysteresis of 40mV.
This pin is also an input to the ADC and the current limit
foldback circuit. A 1000Ω active pull-down discharges
12V
OUT
to ground when the external MOSFET is turned
off.
12V
SENSE
: 12V Supply Current Sense and ADC Input.
Connect this pin to the output of the 12V current sense
resistor. The current limit circuit controls the 12V
GATE
pin
to limit the sense voltage between the 12V
IN
and 12V
SENSE
pins to 50mV or less during start-up and 150mV thereafter.
During start-up a foldback feature reduces the current
limit to 15mV as the 12V
OUT
pin approaches ground. A
circuit breaker, enabled after start-up, trips when the sense
voltage exceeds 50mV for 22μs. To disable current limit,
connect this pin to 12V
IN
.
3V
GATE
: Gate Drive for 3.3V Supply External N-Channel
MOSFET. An internal 20μA current source charges the gate
of the external N-channel MOSFET. An internal clamp limits
the gate voltage to 6.2V above 3V
OUT
. During turn-off a
1.3mA pull-down current discharges 3V
GATE
to ground.
During short-circuit a 310mA pull-down current between
3V
GATE
and 3V
OUT
is activated.
3V
IN
: 3.3V Supply, Current Sense and ADC Input. The 1V
precharge circuit draws its power and reference voltage
from 3V
IN
. An undervoltage lockout circuit, with 10mV
hysteresis, prevents any external MOSFET from turning
on when this pin is below 2.8V.
3V
OUT
: 3.3V Gate Drive Return; Foldback, ADC and Power
Bad Input. Connect this pin to the source of the 3.3V supply
external N-channel MOSFET switch for gate drive return.
Power is considered bad if this pin drops below 2.9V. The
comparator on this pin has a built-in hysteresis of 11mV.
This pin is also an input to the ADC and the current limit
foldback circuit. A 190Ω active pull-down discharges 3V
OUT
to ground when the external MOSFET is turned off.
3V
SENSE
: 3.3V Supply Current Sense and ADC Input.
Connect this pin to the output of the 3.3V current sense
resistor. The current limit circuit controls the 3V
GATE
pin
to limit the sense voltage between the 3V
IN
and 3V
SENSE
pins to 25mV or less during start-up and 75mV thereafter.
During start-up a foldback feature reduces the current
limit to 7.5mV as the 3V
OUT
pin approaches ground. A
circuit breaker, enabled after start-up, trips when the sense
voltage exceeds 25mV for 22μs. To disable current limit,
connect this pin to 3V
IN
.
5V
GATE
: Gate Drive for 5V Supply External N-Channel MOS-
FET. An internal 20μA current source charges the gate of
the external N-channel MOSFET. An internal clamp limits
the gate voltage to 6.2V above 5V
OUT
. During turn-off a
1.3mA pull-down current discharges 5V
GATE
to ground.
During short-circuit a 250mA pull-down current between
5V
GATE
and 5V
OUT
is activated.
5V
IN
: 5V Supply, Current Sense and ADC Input. An under-
voltage lockout circuit, with 16mV or 10mV of hysteresis,
prevents any external MOSFET from turning on when this
pin is below 4.38V or 2.8V depending on the state of the
CFG pin.
