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 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.
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)
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
LTC3226
V
IN
LDO
Automatic Normal-to-Backup
Mode Switchover
6
5
4
VOLTAGE (V)
V
OUT
3
V
IN
2
1
0
–1
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
GATE
V
OUT
LDO_FB
RST_FB
255k
80.6k
5V
C
SC
1.2F
3.83M
1.21M
C
OUT
47μF
CPO
C
SC
= 1.2F
C
OUT
= 47μF
I
LOAD
= 2A
+
–
V
IN
CHARGE
PUMP
CPO
VMID
CPO_FB
GND
3226 TA01a
3226fa
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LINEAR [ LINEAR INTEGRATED SYSTEMS ]
