Datasheet

LTC3375
13
3375fc
For more information www.linear.com/3375
pin FuncTions
ON (Pin 20): Open-Drain Output. When the PB pin is
pressed and released, the signal is debounced and the
ON signal is held HIGH for a minimum time period that
is scaled by the C
T
capacitor. ON is forced low if: a) KILL
is not driven high (by µP) within 10 seconds of the initial
valid PB power turn-on event, b) KILL is driven low during
normal operation, c) PB is pressed and held low for 10
seconds during normal operation, d) a RESET_ALL I
2
C
command is written. This pin can connect directly to a
DC/DC converter enable pin that provides an internal pull-
up. Other
wise a pull-up resistor to an external supply is
required. All associated times are scaled by the C
T
capacitor.
PB (Pin 21): Pushbutton Input. Active low. PB is internally
pulled to V
CC
through a 420k (typical) resistor.
KILL (Pin 22): Kill Input Pin. Forcing KILL low releases
the ON output which in turn is forced low. While KILL is
low, the buck converters will be forced to power down and
will remain powered down for 1 second (scaled by the C
T
capacitor) after KILL returns high. During system turn-
on, this pin is blanked by a 10 second (scaled by the C
T
capacitor) (t
KILLH
) to allow the system to pull KILL high.
If unused, connect to V
CC
.
EN6 (Pin 23): Buck Regulator 6 Enable Input. Active high.
EN5 (Pin 24): Buck Regulator 5 Enable Input. Active high.
FB5 (Pin 25): Buck Regulator 5 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
Connecting FB5 to V
IN5
combines buck regulator 5 with
buck regulator 4 for higher current. Up to 4 converters
may be combined in this way.
V
IN5
(Pin 26): Buck Regulator 5 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
IN4
when buck regulator 5 is combined with buck regulator 4
for higher current.
SW5 (Pin 27): Buck Regulator 5 Switch Node. External
inductor connects to this pin.
SW6 (Pin 28): Buck Regulator 6 Switch Node. External
inductor connects to this pin.
V
IN6
(Pin 29): Buck Regulator 6 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
IN5
when buck regulator 6 is combined with buck regulator5
for higher current.
FB6 (Pin 30): Buck Regulator 6 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
Connecting FB6 to V
IN6
combines buck regulator 6 with
buck regulator 5 for higher current. Up to 4 converters
may be combined in this way.
FB7 (Pin 31): Buck Regulator 7 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
Connecting FB7 to V
IN7
combines buck regulator 7 with
buck regulator 6 for higher current. Up to 4 converters
may be combined in this way.
V
IN7
(Pin 32): Buck Regulator 7 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
IN6
when buck regulator 7 is combined with buck regulator 6
for higher current.
SW7 (Pin 33): Buck Regulator 7 Switch Node. External
inductor connects to this pin.
SW8 (Pin 34): Buck Regulator 8 Switch Node. External
inductor connects to this pin.
V
IN8
(Pin 35): Buck Regulator 8 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
IN7
when buck regulator 8 is combined with buck regulator 7
for higher current.
FB8 (Pin 36): Buck Regulator 8 Feedback Pin. Receives
feedback by a resistor divider connected across the output.
Connecting FB8 to V
IN8
combines buck regulator 8 with
buck regulator 7 for higher current. Up to 4 converters
may be combined in this way.
EN8 (Pin 37): Buck Regulator 8 Enable Input. Active high.
EN7 (Pin 38): Buck Regulator 7 Enable Input. Active high.