LTC3225/LTC3225-1
150mA Supercapacitor
Charger
FEATURES
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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.
Low Noise Constant Frequency Charging of Two
Series Supercapacitors
Automatic Cell Balancing Prevents Capacitor
Overvoltage During Charging
Programmable Charge Current (Up to 150mA)
Selectable 2.4V or 2.65V Regulation per Cell
(LTC3225)
Selectable 2V or 2.25V Regulation per Cell
(LTC3225-1)
Automatic Recharge
I
VIN
= 20μA in Standby Mode
I
COUT
< 1μA When Input Supply is Removed
No Inductors
Tiny Application Circuit (2mm
×
3mm DFN Package,
All Components <1mm High)
APPLICATIONS
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Current Limited Applications with High Peak Power
Loads (LED Flash, PCMCIA Tx Bursts, HDD Bursts,
GPRS/GSM Transmitter)
Backup Supplies
TYPICAL APPLICATION
Charging Profile with 30% Mismatch
in Output Capacitance, C
TOP
< C
BOT
V
IN
2.8V/3V TO 5.5V
V
IN
2.2μF
1μF
C
+
LTC3225 CX
LTC3225-1
–
C
GND
SHDN
V
SEL
PROG
12k
3225 TA01a
C
OUT
0.6F
0.6F
V
OUT
4.8V/5.3V (LTC3225)
4V/4.5V (LTC3225-1)
SHDN
5V/DIV
I
VIN
300mA/DIV
100k
V
COUT
2V/DIV
ON/OFF
OUTPUT
PROGRAMMING
PGOOD
V
TOP
-V
BOT
200mV/DIV
5 SEC/DIV
LTC3225
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
LTC3225/LTC3225-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
C
+
1
C
–
2
CX 3
SHDN
4
PGOOD 5
11
10 C
OUT
9
8
7
6
V
IN
GND
PROG
V
SEL
V
IN
, C
OUT
to GND ......................................... –0.3V to 6V
SHDN,
V
SEL
...................................... –0.3V to V
IN
+ 0.3V
C
OUT
Short-Circuit Duration ............................. Indefinite
I
VIN
Continuous (Note 2) ......................................350mA
I
OUT
Continuous (Note 2) .....................................175mA
Operating Temperature Range (Note 3).... –40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
DDB PACKAGE
10-LEAD (3mm 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 76°C/W
EXPOSED PAD (PIN 11) MUST BE SOLDERED TO
LOW IMPEDANCE GND PLANE (PIN 8) ON PCB
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
LTC3225EDDB#TRMPBF
LTC3225EDDB-1#TRMPBF
TRM = 500 pieces.
TAPE AND REEL
LTC3225EDDB#TRPBF
LTC3225EDDB-1#TRPBF
PART MARKING
LCYR
LFFS
PACKAGE DESCRIPTION
10-Lead (3mm
×
2mm) Plastic DFN
10-Lead (3mm
×
2mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
SYMBOL
LTC3225
V
IN-UVLO
V
IN-UVLO-HYS
V
IN
V
COUT
V
COUT-HYS
V
TOP/BOT
LTC3225-1
V
IN-UVLO
V
IN-UVLO-HYS
Input Supply Undervoltage Lockout
High-to-Low Threshold
Input Supply Undervoltage Lockout
Hysteresis
Input Supply Undervoltage Lockout
High-to-Low Threshold
Input Supply Undervoltage Lockout
Hysteresis
Input Voltage Range
Charge Termination Voltage
Sleep Mode Threshold (Rising Edge)
Output Comparator Hysteresis
Maximum Voltage Across Each of the
Supercapacitors After Charging
PARAMETER
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, C
IN
= 2.2μF C
FLY
= 1μF unless otherwise specified (Note 3).
,
,
CONDITIONS
V
SEL
= V
IN
V
SEL
= 0
V
SEL
= V
IN
V
SEL
= 0
V
SEL
= V
IN
V
SEL
= 0V
V
SEL
= V
IN
V
SEL
= 0V
V
SEL
= V
IN
V
SEL
= 0V
V
SEL
= V
IN
V
SEL
= 0
V
SEL
= V
IN
V
SEL
= 0
l
l
l
l
l
l
l
l
l
l
MIN
2.65
2.4
TYP
2.75
2.5
150
140
MAX
2.85
2.6
UNITS
V
V
mV
mV
3
2.8
5.2
4.7
5.3
4.8
100
5.5
5.5
5.4
4.9
2.75
2.5
V
V
V
V
mV
V
V
V
V
mV
mV
3225fb
2.25
2.0
2.35
2.1
150
140
2.45
2.2
2
LTC3225/LTC3225-1
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
COUT
V
COUT-HYS
V
TOP/BOT
PARAMETER
Input Voltage Range
Charge Termination Voltage
Sleep Mode Threshold (Rising Edge)
Output Comparator Hysteresis
Maximum Voltage Across Each of the
Supercapacitors After Charging
No Load Operating Current at V
IN
Shutdown Current
C
OUT
Leakage Current
V
SEL
= V
IN
V
SEL
= 0
I
OUT
= 0mA
SHDN
= 0V, V
OUT
= 0V
V
OUT
= 5.6V,
SHDN
= 0V
V
OUT
= 5.6V, Charge Pump in Sleep Mode
V
OUT
= 5.6V,
SHDN
Connected to V
IN
with
Input Supply Removed
V
IN
= 3.6V, R
PROG
= 12k, C
TOP
= C
BOT
V
IN
= 3.6V, R
PROG
= 60k, C
TOP
= C
BOT
I
OUT
Output Charge Current
V
IN
= 3.6V, R
PROG
= 12k, C
TOP
= C
BOT
,
V
OUT
= 4.5V (LTC3225),
V
OUT
= 3.7V (LTC3225-1)
V
IN
= 3.6V, R
PROG
= 60k, C
TOP
= C
BOT
,
V
OUT
= 4.5V (LTC3225),
V
OUT
= 3.7V (LTC3225-1)
V
PGOOD
I
PGOOD-LEAK
V
PG
V
PG-HYS
R
OL
f
OSC
V
SEL
,
SHDN
V
IH
V
IL
I
IH
I
IL
Input High Voltage
Input Low Voltage
Input High Current
Input Low Current
l
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, C
IN
= 2.2μF C
FLY
= 1μF unless otherwise specified (Note 3).
,
,
CONDITIONS
V
SEL
= V
IN
V
SEL
= 0
V
SEL
= V
IN
V
SEL
= 0
l
l
l
l
MIN
2.8
2.8
4.4
3.9
TYP
MAX
5.5
5.5
UNITS
V
V
V
V
mV
V
V
μA
μA
μA
μA
μA
mA
mA
4.5
4.0
100
4.6
4.1
2.35
2.1
LTC3225/LTC3225-1
I
Q-VIN
I
SHDN-VIN
I
COUT
20
0.1
1
2
40
1
3
4
1
I
VIN
Input Charge Current
306
55
125
150
175
mA
26
mA
PGOOD Low Output Voltage
PGOOD High Impedance Leakage Current
PGOOD Low-to-High Threshold
PGOOD Threshold Hysteresis
Effective Open-Loop Output Impedance
(Note 4)
CLK Frequency
I
PGOOD
= –1.6mA
V
PGOOD
= 5V
Relative to Output Voltage Threshold
Relative to Output Voltage Threshold
V
IN
= 3.6V, V
OUT
= 4.5V (LTC3225)
V
IN
= 3.6V, V
OUT
= 3.7V (LTC3225-1)
l
l
l
l
0.4
10
92
0.25
94
1.2
8
9
96
2.5
V
μA
%
%
Ω
l
0.6
1.3
0.9
1.5
MHz
V
0.4
–1
–1
1
1
V
μA
μA
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
Based on long-term current density limitations.
Note 3:
The LTC3225/LTC3225-1 are tested under pulsed load conditions
such that T
J
≈ T
A
. The LTC3225/LTC3225-1 are guaranteed to meet
performance specifications from 0°C to 85°C. Specifications over the
–40°C to 85°C operating temperature range are assured by design,
characterization and correlation with statistical process controls.
Note 4:
Output not in regulation;
R
OL
≡
(2 • V
IN
– V
OUT
)/I
OUT
3225fb
3
LTC3225/LTC3225-1
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C, C
FLY
= 1μF C
IN
= 2.2μF C
TOP
= C
BOT
, unless otherwise specified)
,
,
I
OUT
vs R
PROG
160
140
120
I
OUT
(mA)
100
I
OUT
(mA)
80
60
40
20
0
10
20
30
40
R
PROG
(kΩ)
50
60
3225 G01
I
OUT
vs V
OUT
(R
PROG
= 12k)
V
IN
= 3.6V
V
OUT
= 4.5V (LTC3225)
180
160
140
EFFICIENCY (%)
120
100
80
60
40
20
0
0
0.5
1
1.5
2 2.5 3
V
OUT
(V)
3.5
C
TOP
= C
BOT
V
IN
= 2.8V
V
IN
= 3.6V
V
IN
= 5.5V
4
4.5
5
100
90
80
70
60
50
40
30
20
10
0
Efficiency vs V
IN
LTC3225
LTC3225-1
I
LOAD
= 100mA
C
TOP
= C
BOT
V
SEL
= V
IN
V
SEL
= 0
2.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
3525 G03
3225 G02
Extra Input Current vs Output
Current (I
VIN
– 2 • I
OUT
)
7
V
IN
= 3.6V
CHARGE PUMP IS ON
V
OUT
= 5V
EXTRA I
IN
(mA)
20
V
OUT
= 4.5V
V
OUT
= 3.7V
4
10
3
V
OUT
= 4.2V
5
0
I
IN
(μA)
5
15
30
25
No-Load Input Current vs
Supply Voltage
10.0
T
A
= 85°C
T
A
= 25°C
R
OL
(Ω)
T
A
= –40°C
9.5
9.0
8.5
8.0
7.5
7.0
6.5
2.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
3225 G05
Charge Pump Open-Loop Output
Resistance vs Temperature
(2V
IN
– V
COUT
)/I
OUT
V
IN
= 3.6V
V
OUT
= 3.7V
(LTC3225-1)
6
V
OUT
= 4.5V
(LTC3225)
2
20
40
60
80 100
I
OUT
(mA)
120
140
160
6.0
–40
–15
10
35
TEMPERATURE (°C)
60
85
3225 G06
3225 G04
Oscillator Frequency vs
Supply Voltage
0.94
0.93
FREQUENCY (MHz)
0.92
0.91
T
A
= 85°C
0.90
T
A
= 25°C
T
A
= –40°C
I
VIN
200mA/DIV
V
IN
20mV/DIV
Input Ripple and Input Current
SHDN
5V/DIV
I
VIN
300mA/DIV
0mA
V
COUT
2V/DIV
V
TOP
-V
BOT
500mV/DIV
R
PROG
= 12k
200ns/DIV
3225 G08
Charging Profile with Unequal
Initial Output Capacitor Voltage
(Initial V
TOP
= 1.3V, V
BOT
= 1V)
0.89
0.88
2.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
3225 G07
2 SEC/DIV
LTC3225
V
SEL
= V
IN
R
PROG
= 12k
C
TOP
= C
BOT
= 1.1F
C
TOP
INITIAL VOLTAGE = 1.3V
C
BOT
INITIAL VOLTAGE = 1V
3225 G09
3225fb
4
LTC3225/LTC3225-1
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C, C
FLY
= 1μF C
IN
= 2.2μF C
TOP
= C
BOT
, unless otherwise specified)
,
,
Charging Profile with Unequal
Initial Output Capacitor Voltage
(Initial V
TOP
= 1V, V
BOT
= 1.3V)
SHDN
5V/DIV
I
VIN
300mA/DIV
V
COUT
2V/DIV
SHDN
5V/DIV
I
VIN
300mA/DIV
V
COUT
2V/DIV
V
TOP
-V
BOT
200mV/DIV
2 SEC/DIV
LTC3225
V
SEL
= V
IN
R
PROG
= 12k
C
TOP
= C
BOT
= 1.1F
C
TOP
INITIAL VOLTAGE = 1V
C
BOT
INITIAL VOLTAGE = 1.3V
3225 G10
Charging Profile with 30%
Mismatch in Output Capacitance
(C
TOP
> C
BOT
)
SHDN
5V/DIV
I
VIN
300mA/DIV
V
COUT
2V/DIV
V
TOP
-V
BOT
200mV/DIV
5 SEC/DIV
LTC3225
V
SEL
= V
IN
R
PROG
= 12k
C
TOP
= 1.43F
C
BOT
= 1.1F
C
TOP
INITIAL VOLTAGE = 0V
C
BOT
INITIAL VOLTAGE = 0V
3225 G11
Charging Profile with 30%
Mismatch in Output Capacitance
(C
TOP
< C
BOT
)
V
TOP
-V
BOT
500mV/DIV
5 SEC/DIV
LTC3225
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 G12
PIN FUNCTIONS
C
+
(Pin 1):
Flying Capacitor Positive Terminal. A 1μF X5R
or X7R ceramic capacitor should be connected from C
+
to C
–
.
C
–
(Pin 2):
Flying Capacitor Negative Terminal.
CX (Pin 3):
Midpoint of Two Series Supercapacitors. This
pin voltage is monitored and forced to track C
OUT
(CX =
C
OUT
/2) during charging to achieve voltage balancing of
the top and bottom supercapacitors.
SHDN
(Pin 4):
Active Low Shutdown Input. A low on
SHDN
puts the LTC3225/LTC3225-1 in low current shutdown
mode. Do not float the
SHDN
pin.
PGOOD (Pin 5):
Open-Drain Output Status Indicator. Upon
start-up, this open-drain pin remains low until the output
voltage, V
OUT
, is within 6% (typical) of its final value. Once
V
OUT
is valid, PGOOD becomes Hi-Z. If V
OUT
falls 7.2%
(typical) below its correct regulation level, PGOOD is
pulled low. PGOOD may be pulled up through an external
resistor to an appropriate reference level. This pin is Hi-Z
in shutdown mode.
V
SEL
(Pin 6):
Output Voltage Selection Input. A logic
low at V
SEL
sets the regulated C
OUT
to 4.8V (LTC3225)
or 4V (LTC3225-1); a logic high sets the regulated C
OUT
to 5.3V (LTC3225) or 4.5V (LTC3225-1). Do not float the
V
SEL
pin.
PROG (Pin 7):
Charge Current Programming Pin. A resis-
tor connected between this pin and GND sets the charge
current. (See Applications Information section).
GND (Pin 8, Exposed Pad Pin 11):
Charge Pump Ground.
These pins must be soldered directly to PCB ground. The
exposed pad must be soldered to a low impedance PCB
ground for rated thermal performance.
V
IN
(Pin 9):
Power Supply for the LTC3225/LTC3225-1.
V
IN
should be bypassed to GND with a low ESR ceramic
capacitor of more than 2.2μF
.
C
OUT
(Pin 10):
Charge Pump Output Pin. Connect C
OUT
to
the top plate of the top supercapacitor. C
OUT
provides charge
current to the supercapacitors and regulates the final volt-
age to 4.8V/5.3V (LTC3225) or 4V/4.5V (LTC3225-1).
3225fb
5
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