LTC3225-1_15 Datasheet, PDF (1/14 Pages) Linear Technology – 150mA Supercapacitor Charger

FEATURES
n _{Low Noise Constant Frequency Charging of Two}
Series Supercapacitors
n _{Automatic Cell Balancing Prevents Capacitor}
Overvoltage During Charging
n _{Programmable Charge Current (Up to 150mA)}
n _{Selectable 2.4V or 2.65V Regulation per Cell}
(LTC3225)
n _{Selectable 2V or 2.25V Regulation per Cell}
(LTC3225-1)
n _{Automatic Recharge}
n _{IVIN = 20μA in Standby Mode}
n _{ICOUT < 1μA When Input Supply is Removed}
n _{No Inductors}
n _{Tiny Application Circuit (2mm × 3mm DFN Package,}
All Components <1mm High)
APPLICATIONS
n _{Current Limited Applications with High Peak Power}
Loads (LED Flash, PCMCIA Tx Bursts, HDD Bursts,
GPRS/GSM Transmitter)
n _{Backup Supplies}
LTC3225/LTC3225-1
150mA Supercapacitor
Charger
DESCRIPTION
The LTC^®3225/LTC3225-1 are programmable supercapaci-
tor chargers designed to charge two supercapacitors in
series to a selectable fixed output voltage (4.8V/5.3V for
the LTC3225 and 4V/4.5V for the LTC3225-1) from input
supplies as low as 2.8V to 5.5V. Automatic cell balancing
prevents overvoltage damage to either supercapacitor. No
balancing resistors are required.
Low input noise, low quiescent current and low external
parts count (one flying capacitor, one bypass capacitor at
V_IN and one programming resistor) make the LTC3225/
LTC3225-1 ideally suited for small battery-powered
applications.
Charge current level is programmed with an external
resistor. When the input supply is removed, the LTC3225/
LTC3225-1 automatically enter a low current state, drawing
less than 1μA from the supercapacitors.
The LTC3225/LTC3225-1 are available in a 10-lead 2mm
× 3mm DFN package.
L, LT, LTC and LTM are registered trademarks and ThinSOT is a trademark of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V_IN
2.8V/3V TO 5.5V
2.2μF
1μF
ON/OFF
OUTPUT
PROGRAMMING
V_IN
C_OUT
C⁺ LTC3225 CX
LTC3225-1
C^–
GND
SHDN PGOOD
V_OUT
4.8V/5.3V (LTC3225)
0.6F 4V/4.5V (LTC3225-1)
0.6F
100k
V_SEL
PROG
12k
3225 TA01a
SHDN
5V/DIV
I_VIN
300mA/DIV
V_COUT
2V/DIV
Charging Profile with 30% Mismatch
in Output Capacitance, C_TOP < C_BOT
V_TOP-V_BOT
200mV/DIV
LTC3225
5 SEC/DIV
V_SEL = V_IN
R_PROG = 12k
C_TOP = 1.1F
C_BOT = 1.43F
C_TOP INITIAL VOLTAGE = 0V
C_BOT INITIAL VOLTAGE = 0V
3225 TA01b
3225fb
1