Datasheet

LTC3375
12
3375fc
For more information www.linear.com/3375
pin FuncTions
FB1 (Pin 1): Buck Regulator 1 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
V
IN1
(Pin 2): Buck Regulator 1 Input Supply. Bypass to
GND with a 10µF or larger ceramic capacitor.
SW1 (Pin 3): Buck Regulator 1 Switch Node. External
inductor connects to this pin.
SW2 (Pin 4): Buck Regulator 2 Switch Node. External
inductor connects to this pin.
V
IN2
(Pin 5): 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): 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 4 converters
may be combined in this way.
FB3 (Pin 7): Buck Regulator 3 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
Connecting FB3 to V
IN3
combines buck regulator 3 with
buck regulator 2 for higher current. Up to 4 converters
may be combined in this way.
V
IN3
(Pin 8): 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): Buck Regulator 3 Switch Node. External
inductor connects to this pin.
SW4 (Pin 10): Buck Regulator 4 Switch Node. External
inductor connects to this pin.
V
IN4
(Pin 11): 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): Buck Regulator 4 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
Connecting FB4 to V
IN4
combines buck regulator 4 with
buck regulator 3 for higher current. Up to 4 converters
may be combined in this way.
EN4 (Pin 13): Buck Regulator 4 Enable Input. Active high.
EN3 (Pin 14): Buck Regulator 3 Enable Input. Active high.
IRQ (Pin 15): Interrupt Pin (Active Low). Open-drain output.
When an undervoltage, die temperature, or unmasked error
condition is detected, this pin is driven LOW.
RST (Pin 16): Reset Pin (Active Low). Open-drain output.
When the regulated output voltage of any unmasked
enabled switching regulator is more than 7.5% below its
programmed level, this pin is driven LOW. Assertion delay
is scaled by the C
T
capacitor. When all buck regulators are
disabled RST is driven LOW.
CT (Pin 17): Timing Capacitor Pin. A capacitor connected
to GND sets a time constant which is scaled for use by
the ON, KILL, PB, RST and IRQ pins.
SYNC (Pin 18): Oscillator Synchronization Pin. Driving
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. Do not float. SYNC
should be held at ground if not used.
RT (Pin 19): Oscillator Frequency Pin. This pin provides
two modes of setting the switching frequency. Connecting a
resistor from RT to ground will set the switching frequency
based on the resistor value. If RT is tied to V
CC
the default
internal 2MHz oscillator will be used. Do not float.