LTC3225 Datasheet, PDF (1/12 Pages) Linear Technology – 150mA Supercapacitor Charger

LTC3225
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 Charging Current (Up to 150mA)}
n _{Selectable 2.4V or 2.65V Regulation per Cell}
n _{Automatic Recharge}
n _{IVIN = 20μA in Standby Mode}
n _{ICOUT < 1μA When Input Supply is Removed}
n _{No Inductors}
n _{Tiny Application Circuit (3mm × 2mm 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}
DESCRIPTION
The LTC^®3225 is a programmable supercapacitor charger
designed to charge two supercapacitors in series to a
fixed output voltage (4.8V/5.3V selectable) from a 2.8V/3V
to 5.5V input supply. 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
ideally suited for small battery-powered applications.
Charging current level is programmed with an external
resistor. When the input supply is removed, the LTC3225
automatically enters a low current state, drawing less than
1μA from the supercapacitors.
The LTC3225 is available in a 10-lead 3mm × 2mm DFN
package.
L, LT, LTC and LTM are registered trademarks 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⁺
CX
LTC3225
C^–
GND
SHDN PGOOD
V_SEL
PROG
12k
3225 TA01a
V_OUT
4.8V/5.3V
0.6F
0.6F
100k
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
V_SEL = V_IN
5s/DIV
R_PROG = 12k
C_TOP = 1.1F
C_BOT = 1.43F
C_TOP INITIAL VOLTAGE = 0V
C_BOT INITIAL VOLTAGE = 0V
3225 TA01b
3225f
1