LTC3245 Datasheet, PDF (6/16 Pages) Linear Technology – Wide VIN Range, Low Noise, 250mA Buck-Boost Charge Pump

LTC3245
Typical Performance Characteristics T_A = 25°C, unless otherwise noted.
5V Output Transient Response
Burst Mode
OPERATION
AC 50mV/DIV
LOW NOISE
AC 50mV/DIV
200mA
I_OUT 5mA
V_IN = 12V
V_OUT = 5V
3245 G19
3.3V Output Transient Response
Burst Mode
OPERATION
AC 50mV/DIV
LOW NOISE
AC 50mV/DIV
150mA
I_OUT 5mA
V_IN = 12V
V_OUT = 3.3V
3245 G20
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
LOW
LOW
LOW
HIGH
HIGH
LOW
HIGH
HIGH
MODE
Shutdown
Adjustable V_OUT
Fixed 5V
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.
3245f
6
For more information www.linear.com/LTC3245