FEATURES
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LTC3226
2-Cell Supercapacitor
Charger with Backup
PowerPath Controller
DESCRIPTION
The LTC
®
3226 is a 2-cell series supercapacitor charger with
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 from a 2.5V to 5.3V
input supply. The charger input current limit is program-
mable 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.
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1x/2x Multimode Charge Pump Supercapacitor
Charger
Automatic Cell Balancing
Ideal Diode Main PowerPath™ Controller
(V
IN
to V
OUT
)
Internal 2A LDO Backup Supply (CPO to V
OUT
)
Automatic Main/Backup Switchover
Input Voltage Range: 2.5V to 5.5V
Programmable SCAP Charge Voltage
Programmable Input Current Limit (315mA Max)
No Load I
VIN
= 55μA (Typical)
Low Profile, 16-Lead 3mm
×
3mm QFN Package
APPLICATIONS
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Smart Power Meters
Battery-Powered Industrial/Medical Equipment
3.3V Solid-State Drives
Industrial Alarms
Data Backup Supplies
Battery Hold-Up Supplies
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.
TYPICAL APPLICATION
3.3V Backup Supply
MPEXT
TO LOAD
(2A)
LTC3226
LDO
V
IN
3.3V
2.2µF
1.96M
1.2V
PFI
1.21M
2.2µF
C
+
C
–
PROG
33.2k
EN_CHG
PFO
RST
CAPGOOD
Automatic Normal-to-Backup
Mode Switchover
6
C
OUT
47µF
VOLTAGE (V)
5
4
3
2
1
CPO
C
SC
= 1.2F
C
OUT
= 47µF
I
LOAD
= 2A
V
OUT
V
IN
BACKUP
BACKUP MODE
MODE
(LDO IN
(LDO IN
REGULATION) DROPOUT)
PFO
(2V/DIV)
0
0.4
0.8
1.2
TIME (SECONDS)
1.6
2.0
3226 TA01b
V
IN
GATE
V
OUT
LDO_FB
255k
80.6k
5V
C
SC
1.2F
3.83M
1.21M
+
–
RST_FB
CPO
VMID
CHARGE
PUMP
CPO_FB
V
IN
0
–1
GND
3226 TA01a
3226f
1
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
