LTC3226

1

3226fa

TYPICAL APPLICATION

FEATURES

DESCRIPTION

2-Cell Supercapacitor

Charger with Backup

PowerPath Controller

a backup PowerPath controller. It includes a charge pump

supercapacitor charger with programmable output voltage,

a low dropout regulator, and a power-fail comparator for

switching between normal and backup modes.

The constant input current supercapacitor charger is

designed to charge two supercapacitors in series to a

resistor-programmable output voltage of 2.5V to 5.3V.

The charger input current limit is programmable by an

external resistor at up to 315mA.

The internal backup LDO is powered from the superca-

pacitors and provides up to 2A peak output current with

an adjustable output voltage. When the input supply falls

below the power-fail threshold, the LTC3226 automatically

enters a backup state in which the supercapacitors power

the output through the LDO. The input supply power-fail

voltage level is programmed by an external resistor divider.

Low input noise, low quiescent current and a compact

footprint make the LTC3226 ideally suited for small, battery-

powered applications. Internal current limit and thermal

shutdown circuitry allow the device to survive a continu-

ous short-circuit from the PROG or CPO pins to ground.

Automatic Normal-to-Backup

Mode Switchover

3.3V Backup Supply

APPLICATIONS

Charger

× 3mm QFN Package

L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks

and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

1.2V

GATE

MPEXT

PFI

2.2μF

1.96M

PROG

EN_CHG

PFO

RST

CAPGOOD

GND

CHARGE

PUMP

LTC3226

LDO

CPO

5V

VMID

2.2μF

3.3V

1.21M

47μF

TO LOAD

(2A)

33.2k

3.83M

1.2F

255k

80.6k

1.21M

3226 TA01a

CPO_FB

LDO_FB

RST_FB

+

–

TIME (SECONDS)

0

3

4

5

1.6

3226 TA01b

2

1

–1

0.4

0.8

1.2

CPO

2.0

0

6

PFO (2V/DIV)

BACKUP

MODE

(LDO IN

REGULATION)

BACKUP MODE

(LDO IN

DROPOUT)