Datasheet

LTC3245
7
3245fa
For more information www.linear.com/LTC3245
pin FuncTions
V
IN
(Pins 1, 2, 3): Power Input Pins. Input voltage for both
charge pump and IC control circuitry. The V
IN
pin oper-
ates from 2.7V to 38V. All V
IN
pins should be connected
together at pins.
BURST (Pin 4): Burst Mode Logic Input. A logic high on
the BURST pin operates the charge pump in low noise
constant frequency. A logic low will operates the charge
pump in Burst Mode operation for higher efficiency at
low output currents. The BURST pin has a 1μA (typical)
pull-down current to ground and can tolerate 38V inputs
allowing it to be pin-strapped to V
IN
.
SEL1 (Pin 5): Logic Input Pin. See Table 1 for SEL1/SEL2
operating logic. The SEL1 pin has a 1μA (typical) pull-down
current to ground and can tolerate 38V inputs allowing it
to be pin-strapped to V
IN
.
SEL2 (Pin 6): Logic Input Pin. See Table 1 for SEL1/SEL2
operating logic. The SEL2 pin has a 1μA (typical) pull-down
current to ground and can tolerate 38V inputs allowing it
to be pin-strapped to V
IN
.
Table 1: V
OUT
Operating Modes
SEL2 SEL1 MODE
LOW LOW Shutdown
LOW HIGH Adjustable V
OUT
HIGH LOW Fixed 5V
HIGH HIGH Fixed 3.3V
OUTS/ADJ (Pin 7): V
OUT
Sense / Adjust Input Pin. This pin
acts as V
OUT
sense (OUTS) for 5V or 3.3V fixed outputs
and adjust (ADJ) for adjustable output through external
feedback. The ADJ pin servos to 1.2V when the device is
enabled in adjustable mode. (OUTS / ADJ are selected by
SEL1 and SEL2 pins; See Table 1)
PGOOD (Pin 8): Power Good Open Drain Logic Output.
The PGOOD pin goes high impedance when V
OUT
is about
6% of its final operating voltage. PGOOD is intended to
be pulled up to V
OUT
or other low voltage supply with an
external resistor.
C
+
(Pin 9): Flying Capacitor Positive Connection.
V
OUT
(Pin 10): Charge Pump Output Voltage. If V
IN
drops
below its UVLO threshold, the connection from V
IN
be-
comes high impedance with no reverse leakage from
V
OUT
to V
IN
. V
OUT
regulation only takes place above the
UVLO threshold. V
OUT
can be programmed to regulate
from 2.5V to 5V.
C
–
(Pin 11): Flying Capacitor Negative Connection.
GND (Pin 12, Exposed Pad Pin 13): Ground. The exposed
package pad is ground and must be soldered to the PC
board ground plane for proper functionality and for rated
thermal performance.