LTC3226
2-Cell Supercapacitor
Charger with Backup
PowerPath Controller
FEATURES
DESCRIPTION
TheLTC®3226isa2-cellseriessupercapacitorchargerwith
a backup PowerPath controller. It includes a charge pump
supercapacitorchargerwithprogrammableoutputvoltage,
a low dropout regulator, and a power-fail comparator for
switching between normal and backup modes.
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1x/2x Multimode Charge Pump Supercapacitor
Charger
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Automatic Cell Balancing
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Ideal Diode Main PowerPath™ Controller
(V to V
)
IN
OUT
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Internal 2A LDO Backup Supply (CPO to V
Automatic Main/Backup Switchover
Input Voltage Range: 2.5V to 5.5V
Programmable SCAP Charge Voltage
)
OUT
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.
Programmable Input Current Limit (315mA Max)
No Load I = 55μA (Typical)
VIN
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
belowthepower-failthreshold, theLTC3226automatically
enters a backup state in which the supercapacitors power
the output through the LDO. The input supply power-fail
voltagelevelisprogrammedbyanexternalresistordivider.
Low Profile, 16-Lead 3mm × 3mm QFN Package
APPLICATIONS
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Smart Power Meters
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Battery-Powered Industrial/Medical Equipment
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3.3V Solid-State Drives
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Industrial Alarms
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Data Backup Supplies
Low input noise, low quiescent current and a compact
footprintmaketheLTC3226ideallysuitedforsmall,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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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)
Automatic Normal-to-Backup
Mode Switchover
LTC3226
LDO
V
IN
3.3V
GATE
V
6
IN
C
C
= 1.2F
SC
V
2.2ꢀF
OUT
CPO
= 47ꢀF
= 2A
OUT
LOAD
5
4
I
C
OUT
47ꢀF
255k
1.96M
LDO_FB
RST_FB
CPO
V
OUT
80.6k
3
1.2V
PFI
+
–
5V
V
IN
2
+
V
IN
BACKUP
MODE
1.21M
33.2k
C
VMID
C
SC
1.2F
BACKUP MODE
(LDO IN
1
–
2.2ꢀF
(LDO IN
C
DROPOUT)
CHARGE
PUMP
REGULATION)
PROG
0
3.83M
PFO (2V/DIV)
CPO_FB
EN_CHG
–1
0
0.4
0.8
1.2
1.6
2.0
PFO
RST
1.21M
TIME (SECONDS)
CAPGOOD
3226 TA01b
GND
3226 TA01a
3226fa
1