1
LT1511
Constant-Current/
Constant-Voltage 3A Battery
Charger with Input Current Limiting
The LT
®
1511 current mode PWM battery charger is the
simplest, most efficient solution to fast charge modern
rechargeable batteries including lithium-ion (Li-Ion), nickel-
metal-hydride (NiMH) and nickel-cadmium (NiCd) that
require constant-current and/or constant-voltage charg-
ing. The internal switch is capable of delivering 3A* DC
current (4A peak current). Full-charging current can be
programmed by resistors or a DAC to within 5%. With 0.5%
reference voltage accuracy, the LT1511 meets the critical
constant-voltage charging requirement for Li-Ion cells.
A third control loop is provided to regulate the current
drawn from the AC adapter. This allows simultaneous
operation of the equipment and battery charging without
overloading the adapter. Charging current is reduced to
keep the adapter current within specified levels.
The LT1511 can charge batteries ranging from 1V to 20V.
Ground sensing of current is not required and the battery's
negative terminal can be tied directly to ground. A saturat-
ing switch running at 200kHz gives high charging effi-
ciency and small inductor size. A blocking diode is not
required between the chip and the battery because the
chip goes into sleep mode and drains only 3
µ
A when the
wall adapter is unplugged.
Figure 1. 3A Lithium-Ion Battery Charger
SW
BOOST
COMP1
CLN
UV
OVP SENSE
BAT
C1
1
µ
F
R
S4
ADAPTER
CURRENT SENSE
R7
500
R5
UNDERVOLTAGE
LOCKOUT
R6
5k
V
IN
(ADAPTER INPUT)
11V TO 28V
V
BAT
10
µ
F
C
PROG
1
µ
F
C
IN
*
10
µ
F
300
R
PROG
4.93k
1%
0.33
µ
F
1k
C2
0.47
µ
F
R
S3
200
1%
R
S2
200
1%
L1**
20
µ
H
D2
MBR0540T
200pF
R
S1
0.033
BATTERY CURRENT
SENSE
R3
390k
0.25%
BATTERY
VOLTAGE SENSE
R4
162k
0.25%
50pF
C
OUT
22
µ
F
TANT
4.2V
4.2V
+
+
LT1511
NOTE: COMPLETE LITHIUM-ION CHARGER,
NO TERMINATION REQUIRED. R
S4
, R7
AND C1 ARE OPTIONAL FOR I
IN
LIMITING
*TOKIN OR UNITED CHEMI-CON/MARCON
CERAMIC SURFACE MOUNT
**20
µ
H COILTRONICS CTX20-4
SEE APPLICATIONS INFORMATION FOR
INPUT CURRENT LIMIT AND UNDERVOLTAGE LOCKOUT
V
CC
TO MAIN
SYSTEM POWER
SPIN
D1
MBRD340
GND
CLP
2 Li-Ion
D3
MBRD340
1511 · F01
PROG
V
C
+
+
+
, LTC and LT are registered trademarks of Linear Technology Corporation.
*See LT1510 for 1.5A Charger
s
Chargers for NiCd, NiMH, Lead-Acid, Lithium
Rechargeable Batteries
s
Switching Regulators with Precision Current Limit
s
Simple Design to Charge NiCd, NiMH and Lithium
Rechargeable Batteries--Charging Current
Programmed by Resistors or DAC
s
Adapter Current Loop Allows Maximum Possible
Charging Current During Computer Use
s
Precision 0.5% Accuracy for Voltage Mode Charging
s
High Efficiency Current Mode PWM with 4A Internal
Switch
s
5% Charging Current Accuracy
s
Adjustable Undervoltage Lockout
s
Automatic Shutdown When AC Adapter is Removed
s
Low Reverse Battery Drain Current: 3
µ
A
s
Current Sensing Can Be at Either Terminal of the Battery
s
Charging Current Soft-Start
s
Shutdown Control
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LT1511
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
ORDER PART
NUMBER
LT1511CSW
LT1511ISW
T
JMAX
= 125
°
C,
JA
= 30
°
C/ W**
1
2
3
4
5
6
7
8
9
10
11
12
TOP VIEW
SW PACKAGE
24-LEAD PLASTIC SO WIDE
24
23
22
21
20
19
18
17
16
15
14
13
GND**
SW
BOOST
GND**
GND**
UV
GND**
OVP
CLP
CLN
COMP1
SENSE
GND**
GND**
V
CC1
*
V
CC2
*
V
CC3
*
PROG
V
C
UV
OUT
GND**
COMP2
BAT
SPIN
Consult factory for Military grade parts.
*ALL V
CC
PINS SHOULD
BE CONNECTED
TOGETHER CLOSE TO
THE PINS
** ALL GND PINS ARE
FUSED TO INTERNAL DIE
ATTACH PADDLE FOR
HEAT SINKING. CONNECT
THESE PINS TO
EXPANDED PC LANDS
FOR PROPER HEAT
SINKING. 30
°
C/W
THERMAL RESISTANCE
ASSUMES AN INTERNAL
GROUND PLANE
DOUBLING AS A HEAT
SPREADER
(Note 1)
Supply Voltage
(V
MAX
, CLP and CLN Pin Voltage) ...................... 30V
Switch Voltage with Respect to GND ...................... 3V
Boost Pin Voltage with Respect to V
CC
................... 25V
Boost Pin Voltage with Respect to GND ................. 57V
Boost Pin Voltage with Respect to SW Pin .............. 30V
V
C
, PROG, OVP Pin Voltage ...................................... 8V
I
BAT
(Average) ........................................................... 3A
Switch Current (Peak) .............................................. 4A
Operating Junction Temperature Range
Commercial ........................................... 0
°
C to 125
°
C
Industrial ......................................... 40
°
C to 125
°
C
Operating Ambient Temperature
Commercial ............................................ 0
°
C to 70
°
C
Industrial ........................................... 40
°
C to 85
°
C
Storage Temperature Range ................. 65
°
C to 150
°
C
Lead Temperature (Soldering, 10 sec).................. 300
°
C
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
°
C. V
CC
= 16V, V
BAT
= 8V, V
MAX
(maximum operating V
CC
) = 28V,
R
S2
= R
S3
= 200
(see Block Diagram), V
CLN
= V
CC
. No load on any outputs unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Overall
Supply Current
V
PROG
= 2.7V, V
CC
20V
q
4.5
6.8
mA
V
PROG
= 2.7V, 20V < V
CC
25V
q
4.6
7.0
mA
Sense Amplifier CA1 Gain and Input Offset Voltage
8V
V
CC
25V , 0V
V
BAT
20V
(With R
S2
= 200
, R
S3
= 200
)
R
PROG
= 4.93k
q
95
100
105
mV
(Measured across R
S1
)(Note 2)
R
PROG
= 49.3k
q
8
10
12
mV
T
J
< 0
°
C
7
13
mV
V
CC
= 28V, V
BAT
= 20V
R
PROG
= 4.93k
q
90
110
mV
R
PROG
= 49.3k
q
7
13
mV
T
J
< 0
°
C
6
14
mV
V
CC
Undervoltage Lockout (Switch OFF) Threshold
Measured at UV Pin
q
6
7
8
V
UV Pin Input Current
0.2V
V
UV
8V
q
0.1
5
µ
A
UV Output Voltage at UV
OUT
Pin
In Undervoltage State, I
UVOUT
= 70
µ
A
q
0.1
0.5
V
UV Output Leakage Current at UV
OUT
Pin
8V
V
UV
, V
UVOUT
= 5V
q
0.1
3
µ
A
Reverse Current from Battery (When V
CC
Is
V
BAT
20V, V
UV
0.4V
3
15
µ
A
Not Connected, V
SW
Is Floating)
3
LT1511
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
°
C. V
CC
= 16V, V
BAT
= 8V, V
MAX
(maximum operating V
CC
) = 28V,
R
S2
= R
S3
= 200
(see Block Diagram), V
CLN
= V
CC
. No load on any outputs unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Overall
Boost Pin Current
V
CC
= 20V, V
BOOST
= 0V
0.1
10
µ
A
V
CC
= 28V, V
BOOST
= 0V
0.25
20
µ
A
2V
V
BOOST
V
CC
< 8V (Switch ON)
6
9
mA
8V
V
BOOST
V
CC
25V (Switch ON)
8
12
mA
Switch
Switch ON Resistance
8V
V
CC
V
MAX
, I
SW
= 3A,
V
BOOST
V
SW
2V
q
0.15
0.25
I
BOOST
/
I
SW
During Switch ON
V
BOOST
= 24V, I
SW
3A
25
35
mA/A
Switch OFF Leakage Current
V
SW
= 0V, V
CC
20V
q
2
100
µ
A
20V < V
CC
28V
q
4
200
µ
A
Minimum I
PROG
for Switch ON
q
2
4
20
µ
A
Minimum I
PROG
for Switch OFF at V
PROG
1V
q
1
2.4
mA
Maximum V
BAT
for Switch ON
q
V
CC
2
V
Current Sense Amplifier CA1 Inputs (Sense, BAT)
Input Bias Current
q
50
125
µ
A
Input Common Mode Low
q
0.25
V
Input Common Mode High
q
V
CC
2
V
SPIN Input Current
100
200
µ
A
Reference
Reference Voltage (Note 3)
R
PROG
= 4.93k, Measured at OVP with
VA Supplying I
PROG
and Switch OFF
2.453
2.465
2.477
V
Reference Voltage
All Conditions of V
CC
, T
J
> 0
°
C
q
2.441
2.489
V
T
J
< 0
°
C (Note 4)
q
2.43
2.489
V
Oscillator
Switching Frequency
180
200
220
kHz
Switching Frequency
All Conditions of V
CC
, T
J
> 0
°
C
q
170
200
230
kHz
T
J
< 0
°
C
q
160
230
kHz
Maximum Duty Cycle
q
85
%
T
A
= 25
°
C
90
93
%
Current Amplifier CA2
Transconductance
V
C
= 1V, I
VC
=
±
1
µ
A
150
250
550
µ
mho
Maximum V
C
for Switch OFF
q
0.6
V
I
VC
Current (Out of Pin)
V
C
0.6V
100
µ
A
V
C
< 0.45V
3
mA
4
LT1511
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
°
C. V
CC
= 16V, V
BAT
= 8V, V
MAX
(maximum operating V
CC
) = 28V.
No load on any outputs unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Voltage Amplifier VA
Transconductance (Note 3)
Output Current from 50
µ
A to 500
µ
A
0.25
0.6
1.3
mho
Output Source Current
V
OVP
= V
REF
+ 10mV, V
PROG
= V
REF
+ 10mV
1.1
mA
OVP Input Bias Current
At 0.75mA VA Output Current
±
3
±
10
nA
At 0.75mA VA Output Current, T
J
> 90
°
C
15
25
nA
Current Limit Amplifier CL1, 8V
Input Common Mode
Turn-On Threshold
0.75mA Output Current
93
100
107
mV
Transconductance
Output Current from 50
µ
A to 500
µ
A
0.5
1
2
mho
CLP Input Current
0.75mA Output Current, V
UV
0.4V
0.3
1
µ
A
CLN Input Current
0.75mA Output Current V
UV
0.4V
0.8
2
mA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Tested with Test Circuit 1.
Note 3: Tested with Test Circuit 2.
Note 4: A linear interpolation can be used for reference voltage
specification between 0
°
C and 40
°
C.
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Thermally Limited Maximum
Charging Current
Efficiency of Figure 1 Circuit
DUTY CYCLE (%)
0
10
30
50
70
I
CC
(mA)
80
1511 · TPC03
20
40
60
8
7
6
5
4
3
2
1
0
125
°
C
0
°
C
25
°
C
V
CC
= 16V
I
CC
vs Duty Cycle
INPUT VOLTAGE (V)
5
MAXIMUM CHARGING CURRENT (A)
3.0
2.8
2.6
2.4
2.2
2.0
25
1511 · TPC01
10
15
20
30
(
JA
=30
°
C/W)
T
AMAX
= 60
°
C
T
JMAX
=125
°
C
4.2V BATTERY
V
IN
8V
8.4V BATTERY
V
IN
11V
12.6V BATTERY
16.8V BATTERY
NOTE: FOR 4.2V AND 8.4V BATTERIES MAXIMUM
CHARGING CURRENT IS 3A FOR V
IN
V
BAT
3V
I
BAT
(A)
0.2
EFFICIENCY (%)
100
98
96
94
92
90
88
86
84
82
80
1.0
1.8
3.0
2.6
2.2
1511 · TPC02
0.6
1.4
V
IN
= 16.5
V
BAT
= 8.4V
CHARGER EFFICIENCY
INCLUDES LOSS
IN DIODE D3
5
LT1511
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Switching Frequency vs
Temperature
V
REF
Line Regulation
TEMPERATURE (
°
C)
20
FREQUENCY (kHz)
20
0
40
80
120
60
100
140
1511 · TPC04
210
205
200
195
190
185
180
V
CC
(V)
0
I
CC
(mA)
7.0
6.5
6.0
5.5
5.0
4.5
5
10
15
20
1511 · TPC05
25
30
125
°
C
25
°
C
0
°
C
MAXIMUM DUTY CYCLE
I
CC
vs V
CC
V
CC
(V)
0
V
REF
(V)
0.003
0.002
0.001
0
0.001
0.002
0.003
5
10
15
20
1511 · TPC06
25
30
ALL TEMPERATURES
V
C
Pin Characteristics
Maximum Duty Cycle
I
VA
vs
V
OVP
(Voltage Amplifier)
I
VA
(mA)
0
V
OVP
(mV)
4
3
2
1
0
0.8
1511· TPC07
0.2
0.1
0.3
0.5
0.7
0.9
0.4
0.6
1.0
125
°
C
25
°
C
TEMPERATURE (
°
C)
0
DUTY CYCLE (%)
120
1511 · TPC08
40
80
98
97
96
95
94
93
92
91
90
20
60
100
140
V
C
(V)
0
0.2
0.6
1.0
1.4
1.8
I
VC
(mA)
1.20
1.08
0.96
0.84
0.72
0.60
0.48
0.36
0.24
0.12
0
0.12
1.6
1511 · TPC09
0.4
0.8
1.2
2.0
Switch Current vs Boost Current
vs Boost Voltage
SWITCH CURRENT (A)
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4
1.8 2.0
1.6
BOOST CURRENT (mA)
50
45
40
35
30
25
20
15
10
5
0
1511 · TPC11
V
CC
= 16V
V
BOOST
= 38V
28V
18V
TEMPERATURE
0
REFERENCE VOLTAGE (V)
2.470
2.468
2.466
2.464
2.462
2.460
2.458
25
50
75
100
LT1511 · TPC12
125
150
Reference Voltage
vs Temperature
PROG Pin Characteristics
V
PROG
(V)
0
1
2
3
5
4
I
PROG
(mA)
6
0
6
1511 · TPC10
125
°
C
25
°
C
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