LTC4412
6
4412fb
For more information www.linear.com/LTC4412
pin FuncTions
V
IN
(Pin 1): Primary Input Supply Voltage. Supplies power
to the internal circuitry and is one of two voltage sense
inputs to the internal analog controller (The other input
to the controller is the SENSE pin). This input is usually
supplied power from a battery or other power source which
supplies current to the load. This pin can be bypassed to
ground with a capacitor in the range of 0.1µF to 10µF if
needed to suppress load transients.
GND (Pin 2): Ground. Provides a power return for all the
internal circuits.
CTL (Pin 3): Digital Control Input. A logical high input
(V
IH
) on this pin forces the gate to source voltage of the
primary P-channel MOSFET power switch to a small voltage
(V
GOFF
). This will turn the MOSFET off and no current will
flow from the primary power input at V
IN
if the MOSFET
is configured so that the drain to source diode does not
forward bias. A high input also forces the STAT pin to
sink 10µA of current (I
S(SNK)
). If the STAT pin is used to
control an auxiliary P-channel power switch, then a second
active source of power, such as
an AC wall adaptor, will
be connected to the load (see Applications Information).
An internal current
sink will pull the CTL pin voltage to
ground (logical low) if the pin is open.
STAT (Pin 4): Open-Drain Output Status Pin. When the
SENSE pin is pulled above the V
IN
pin with an auxiliary
power source by about 20mV or more, the reverse turn-
off threshold (V
RTO
) is reached. The STAT pin will then go
from an open state to a 10µA current sink (I
S(SNK)
). The
STAT pin current sink can be used, along with an external
resistor, to turn on an auxiliary P-channel power switch
and/or signal the presence of an auxiliary power source
to a microcontroller.
GATE (Pin 5): Primary P-Channel MOSFET Power Switch
Gate Drive Pin. This pin is directed by the power controller
to maintain a forward regulation voltage (V
FR
) of 20mV
between the V
IN
and SENSE pins when an auxiliary power
source is not present. When an auxiliary power source
is connected, the GATE pin will pull up to the SENSE pin
voltage, turning off the primary P-channel power switch.
SENSE (Pin 6): Power Sense Input Pin. Supplies power
to
the internal circuitry and is a voltage sense input to the
internal analog controller
(The other input to the controller
is the V
IN
pin). This input is usually supplied power from
an auxiliary source such as an AC adapter or back-up
battery which also supplies current to the load.
block DiagraM
–
+
1 6
SOURCE
POWER
VOLTAGE/CURRENT
REFERENCE
0.5V
POWER
LINEAR GATE
DRIVER AND
VOLTAGE CLAMP
A1
V
IN
SENSE
ANALOG CONTROLLER
–
+
C1
3
2
CTL
3.5µA
ON/OFF
10µA
*DRAIN-SOURCE DIODE OF MOSFET
STATUS
OUTPUT
4412 BD
ON/OFF
STAT
V
CC
GATE
4
5
GND
OUTPUT
TO LOAD
SELECTOR
–
+
PRIMARY
SUPPLY
–
+
AUXILIARY
SUPPLY
–
+
