LTC3374
11
3374fc
For more information www.linear.com/LTC3374
PIN FUNCTIONS
(QFN/TSSOP)
FB1 (Pin 1/Pin 4): Buck Regulator 1 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
V
IN1
(Pin 2/Pin 5): Buck Regulator 1 Input Supply. Bypass
to GND with a 10µF or larger ceramic capacitor.
SW1 (Pin 3/Pin 6): Buck Regulator 1 Switch Node. External
inductor connects to this pin.
SW2 (Pin 4/Pin 7): Buck Regulator 2 Switch Node. External
inductor connects to this pin.
V
IN2
(Pin 5/Pin 8): Buck Regulator 2 Input Supply. Bypass
to GND with a 10µF or larger ceramic capacitor. May be
driven by an independent supply or must be shorted to V
IN1
when buck regulator 2 is combined with buck regulator 1
for higher current.
FB2 (Pin 6/Pin 9): Buck Regulator 2 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
Connecting FB2 to V
IN2
combines buck regulator 2 with
buck regulator 1 for higher current. Up to four converters
may be combined in this way.
FB3 (Pin 7/Pin 10): Buck Regulator 3 Feedback Pin.
Receives feedback by a resistor divider connected across
the output. Connecting FB3 to V
IN3
combines buck regula-
tor3 with buck regulator 2 for higher current. Up to four
converters may be combined in this way.
V
IN3
(Pin 8/Pin 11): Buck Regulator 3 Input Supply. Bypass
to GND with a 10µF or larger ceramic capacitor. May be
driven by an independent supply or must be shorted to V
IN2
when buck regulator 3 is combined with buck regulator 2
for higher current.
SW3 (Pin 9/Pin 12): Buck Regulator 3 Switch Node.
External inductor connects to this pin.
SW4 (Pin 10/Pin 13): Buck Regulator 4 Switch Node.
External inductor connects to this pin.
V
IN4
(Pin 11/Pin 14): Buck Regulator 4 Input Supply.
Bypass to GND with a 10µF or larger ceramic capacitor.
May be driven by an independent supply or must be
shorted to V
IN3
when buck regulator 4 is combined with
buck regulator 3 for higher current.
FB4 (Pin 12/Pin 15): Buck Regulator 4 Feedback Pin.
Receives feedback by a resistor divider connected across
the output. Connecting FB4 to V
IN4
combines buck regula-
tor
4 with buck regulator 3 for higher current. Up to four
converters may be combined in this way.
EN4 (Pin 13/Pin 16): Buck Regulator 4 Enable Input.
Active high.
EN3 (Pin 14/Pin 17): Buck Regulator 3 Enable Input.
Active high.
PGOOD_ALL (Pin 15/Pin 18): PGOOD Status Pin. Open-
drain output. When the regulated output voltage of any
enabled switching regulator is more than 7.5% below its
programmed level, this pin is
driven LOW. When all buck
regulators are disabled PGOOD_ALL is driven LOW.
SYNC (Pin 16/Pin 19): Oscillator Synchronization Pin. Driv-
ing SYNC with an external clock signal will synchronize all
switchers to the applied frequency. The slope compensation
is automatically adapted to the external clock frequency.
The absence of an external clock signal will enable the
frequency programmed by the RT pin. SYNC should be
held at
ground if not used. Do not float.
RT (Pin 17/Pin 20): Oscillator Frequency Pin. This pin
provides two modes of setting the switching frequency.
Connecting a resistor from RT to ground will set the switch-
ing frequency based on the resistor value. If RT is tied to
V
CC
the internal 2MHz oscillator will be used. Do not float.
EN6 (Pin 18/Pin 21): Buck Regulator 6 Enable Input.
Active
high.
EN5 (Pin 19/Pin 22): Buck Regulator 5 Enable Input.
Active high.
FB5 (Pin 20/Pin 23): Buck Regulator 5 Feedback Pin.
Receives feedback by a resistor divider connected across
the output. Connecting FB5 to V
IN5
combines buck regula-
tor 5 with buck regulator 4 for higher current. Up to four
converters may be combined in this way.
