LTC3225EDDB#PBF Linear Technology, LTC3225EDDB#PBF Datasheet - Page 6

• Manufacturer Part Number: LTC3225EDDB#PBF
• Manufacturer: Linear Technology

Specifications of LTC3225EDDB#PBF

• Lead Free Status / Rohs Status: Compliant

OPERATION
LTC3225/LTC3225-1
The LTC3225/LTC3225-1 are dual cell supercapacitor char-
gers. Their unique topology maintains a constant output
voltage with programmable charge current. Their ability
to maintain equal voltages on both cells while charging
protects the supercapacitors from damage that is possible
with other charging methods, without the use of external
balancing resistors. The LTC3225/LTC3225-1 include an
internal switched capacitor charge pump to boost V
regulated output voltage. A unique architecture maintains
relatively constant input current for the lowest possible
input noise. The basic charger circuit requires only three
external components.
SIMPLIFIED BLOCK DIAGRAM
6
R
PROG
7
6
PROG
V
1.067V (LTC3225-1)
SEL
1.088V (LTC3225)
1.2V
RUN
i
1.2V
V
REF
RUN/STOP
9
V
IN
3000i
C1
OSCILLATOR
IN
1
CHARGE
C
PUMP
to a
+
C
–
+
FLY
Figure 1
CLK
2
V
C
REF
V
–
REF
– 7.2%
Normal Charge Cycle
Operation begins when the SHDN pin is pulled above 1.3V.
The C
voltage threshold using an internal resistor divider and
a comparator. The preset voltage threshold is selectable
with the V
than the preset voltage threshold, the oscillator is enabled.
The oscillator operates at a typical frequency of 0.9MHz.
When the oscillator is enabled, the charge pump operates
charging up C
from shutdown, the input current drawn by the internal
charge pump ramps up at approximately 20mA/μs until it
reaches a level which is determined by R
– 6%
SHUTDOWN CONTROL
SOFT-START AND
V
REF
OUT
4
– 2%
SHDN
pin voltage is sensed and compared with a preset
SEL
pin. If the voltage at the C
OUT
. Each time the charge pump starts up
+
–
UVLO
POR
V
IN
C2
R1
R2
PROTECTION
POR
THERMAL
PGOOD
C
GND
OUT
CX
3225 F01
10
3
8
5
OUT
PROG
C
C
pin is lower
TOP
BOT
.
3225fb