FEATURES
s
LT1511
Constant-Current/
Constant-Voltage 3A Battery
Charger with Input Current Limiting
DESCRIPTIO
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 3µA when the
wall adapter is unplugged.
R7
†
500Ω
GND
SW
BOOST
LT1511
COMP1
200pF
SPIN
OVP SENSE
CLP
CLN
V
CC
C1
1µF
D3
MBRD340
R
S4
†
ADAPTER
CURRENT SENSE
V
IN
(ADAPTER INPUT)
11V TO 28V
TO MAIN
SYSTEM POWER
R5
†
UNDERVOLTAGE
LOCKOUT
R6
5k
300Ω
1k
0.33µF
C
PROG
1µF
R
PROG
4.93k
1%
s
s
s
s
s
s
s
s
s
s
Simple Design to Charge NiCd, NiMH and Lithium
Rechargeable Batteries—Charging Current
Programmed by Resistors or DAC
Adapter Current Loop Allows Maximum Possible
Charging Current During Computer Use
Precision 0.5% Accuracy for Voltage Mode Charging
High Efficiency Current Mode PWM with 4A Internal
Switch
5% Charging Current Accuracy
Adjustable Undervoltage Lockout
Automatic Shutdown When AC Adapter is Removed
Low Reverse Battery Drain Current: 3µA
Current Sensing Can Be at Either Terminal of the Battery
Charging Current Soft-Start
Shutdown Control
APPLICATIO S
s
s
Chargers for NiCd, NiMH, Lead-Acid, Lithium
Rechargeable Batteries
Switching Regulators with Precision Current Limit
, LTC and LT are registered trademarks of Linear Technology Corporation.
*See LT1510 for 1.5A Charger
TYPICAL APPLICATIO
D1
MBRD340
L1**
20µH
C2
0.47µF
+
10µF
+
C
IN
*
10µF
D2
MBR0540T
UV
PROG
V
C
BAT
R
S2
200Ω
1%
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
**20µH COILTRONICS CTX20-4
†
SEE APPLICATIONS INFORMATION FOR
INPUT CURRENT LIMIT AND UNDERVOLTAGE LOCKOUT
R
S3
200Ω
1%
R
S1
0.033Ω
BATTERY CURRENT
SENSE
R3
390k
0.25%
BATTERY
VOLTAGE SENSE
R4
162k
0.25%
+
C
OUT
22µF
TANT
50pF
Figure 1. 3A Lithium-Ion Battery Charger
U
U
U
+
4.2V
+
4.2V
V
BAT
2 Li-Ion
1511 • F01
1
LT1511
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
GND** 1
SW 2
BOOST 3
GND** 4
GND** 5
UV 6
GND** 7
OVP 8
CLP 9
CLN 10
COMP1 11
SENSE 12
24 GND**
23 GND**
22 V
CC1
*
21 V
CC2
*
20 V
CC3
*
19 PROG
18 V
C
17 UV
OUT
16 GND**
15 COMP2
14 BAT
13 SPIN
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
ORDER PART
NUMBER
LT1511CSW
LT1511ISW
*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
SW PACKAGE
24-LEAD PLASTIC SO WIDE
T
JMAX
= 125°C,
θ
JA
= 30°C/ W**
Consult factory for Military grade parts.
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
= 200Ω (see Block Diagram), V
CLN
= V
CC
. No load on any outputs unless otherwise noted.
PARAMETER
Overall
Supply Current
Sense Amplifier CA1 Gain and Input Offset Voltage
(With R
S2
= 200Ω, R
S3
= 200Ω)
(Measured across R
S1
)(Note 2)
V
PROG
= 2.7V, V
CC
≤
20V
V
PROG
= 2.7V, 20V < V
CC
≤
25V
8V
≤
V
CC
≤
25V , 0V
≤
V
BAT
≤
20V
R
PROG
= 4.93k
R
PROG
= 49.3k
T
J
< 0°C
V
CC
= 28V, V
BAT
= 20V
R
PROG
= 4.93k
R
PROG
= 49.3k
T
J
< 0°C
Measured at UV Pin
0.2V
≤
V
UV
≤
8V
In Undervoltage State, I
UVOUT
= 70µA
8V
≤
V
UV
, V
UVOUT
= 5V
V
BAT
≤
20V, V
UV
≤
0.4V
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
MAX
UNITS
4.5
4.6
95
8
7
90
7
6
6
7
0.1
0.1
0.1
3
100
10
6.8
7.0
105
12
13
110
13
14
8
5
0.5
3
15
q
q
q
q
q
q
V
CC
Undervoltage Lockout (Switch OFF) Threshold
UV Pin Input Current
UV Output Voltage at UV
OUT
Pin
UV Output Leakage Current at UV
OUT
Pin
Reverse Current from Battery (When V
CC
Is
Not Connected, V
SW
Is Floating)
2
U
W
U
U
W W
W
mA
mA
mV
mV
mV
mV
mV
mV
V
µA
V
µA
µA
LT1511
ELECTRICAL CHARACTERISTICS
PARAMETER
Overall
Boost Pin Current
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
= 200Ω (see Block Diagram), V
CLN
= V
CC
. No load on any outputs unless otherwise noted.
CONDITIONS
MIN
TYP
MAX
UNITS
µA
µA
mA
mA
V
CC
= 20V, V
BOOST
= 0V
V
CC
= 28V, V
BOOST
= 0V
2V
≤
V
BOOST
– V
CC
< 8V (Switch ON)
8V
≤
V
BOOST
– V
CC
≤
25V (Switch ON)
8V
≤
V
CC
≤
V
MAX
, I
SW
= 3A,
V
BOOST
– V
SW
≥
2V
V
BOOST
= 24V, I
SW
≤
3A
V
SW
= 0V, V
CC
≤
20V
20V < V
CC
≤
28V
q
q
q
q
q
0.1
0.25
6
8
10
20
9
12
Switch
Switch ON Resistance
∆I
BOOST
/∆I
SW
During Switch ON
Switch OFF Leakage Current
Minimum I
PROG
for Switch ON
Minimum I
PROG
for Switch OFF at V
PROG
≤
1V
Maximum V
BAT
for Switch ON
Current Sense Amplifier CA1 Inputs (Sense, BAT)
Input Bias Current
Input Common Mode Low
Input Common Mode High
SPIN Input Current
Reference
Reference Voltage (Note 3)
Reference Voltage
Oscillator
Switching Frequency
Switching Frequency
Maximum Duty Cycle
T
A
= 25°C
Current Amplifier CA2
Transconductance
Maximum V
C
for Switch OFF
I
VC
Current (Out of Pin)
V
C
≥
0.6V
V
C
< 0.45V
V
C
= 1V, I
VC
=
±1µA
q
q
q
q
q
0.15
25
2
4
2
1
4
2.4
0.25
35
100
200
20
Ω
mA/A
µA
µA
µA
mA
V
CC
– 2
V
µA
V
– 50
– 0.25
– 125
V
CC
– 2
– 100
– 200
V
µA
R
PROG
= 4.93k, Measured at OVP with
VA Supplying I
PROG
and Switch OFF
All Conditions of V
CC
, T
J
> 0°C
T
J
< 0°C (Note 4)
q
q
2.453
2.441
2.43
2.465
2.477
2.489
2.489
V
V
V
180
All Conditions of V
CC
, T
J
> 0°C
T
J
< 0°C
q
q
q
200
200
220
230
230
kHz
kHz
kHz
%
%
µmho
V
µA
mA
170
160
85
90
93
150
250
550
0.6
100
3
3
LT1511
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
Voltage Amplifier VA
Transconductance (Note 3)
Output Source Current
OVP Input Bias Current
Current Limit Amplifier CL1, 8V
≤
Input Common Mode
Turn-On Threshold
Transconductance
CLP Input Current
CLN Input Current
0.75mA Output Current
Output Current from 50µA to 500µA
0.75mA Output Current, V
UV
≥
0.4V
0.75mA Output Current V
UV
≥
0.4V
93
0.5
100
1
0.3
0.8
107
2
1
2
mV
mho
µA
mA
Output Current from 50µA to 500µA
V
OVP
= V
REF
+ 10mV, V
PROG
= V
REF
+ 10mV
At 0.75mA VA Output Current
At 0.75mA VA Output Current, T
J
> 90°C
0.25
1.1
±3
– 15
±10
25
0.6
1.3
mho
mA
nA
nA
CONDITIONS
MIN
TYP
MAX
UNITS
ELECTRICAL CHARACTERISTICS
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 PERFORMANCE CHARACTERISTICS
Thermally Limited Maximum
Charging Current
3.0
MAXIMUM CHARGING CURRENT (A)
100
12.6V BATTERY
2.8
8.4V BATTERY
V
IN
≥
11V
2.6
4.2V BATTERY
V
IN
≥
8V
16.8V BATTERY
EFFICIENCY (%)
I
CC
(mA)
2.4
2.2
(θ
JA
=30°C/W)
T
AMAX
=60°C
T
JMAX
=125°C
5
10
20
15
INPUT VOLTAGE (V)
25
30
1511 • TPC01
2.0
NOTE: FOR 4.2V AND 8.4V BATTERIES MAXIMUM
CHARGING CURRENT IS 3A FOR V
IN
– V
BAT
≥
3V
4
U W
Efficiency of Figure 1 Circuit
8
V
IN
= 16.5
V
BAT
= 8.4V
98
96
94
92
90
88
86
84
82
80
0.2
0.6
1.0
1.4 1.8
I
BAT
(A)
2.2
2.6
3.0
INCLUDES LOSS
IN DIODE D3
CHARGER EFFICIENCY
I
CC
vs Duty Cycle
V
CC
= 16V
7
6
5
0°C
4
3
2
1
0
0
10
20
30 40 50 60
DUTY CYCLE (%)
70
80
25°C
125°C
1511 • TPC02
1511 • TPC03
LT1511
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Frequency vs
Temperature
210
205
FREQUENCY (kHz)
200
I
CC
(mA)
6.0
195
190
185
180
–20
5.0
125°C
5.5
∆V
REF
(V)
0
20
40 60 80 100 120 140
TEMPERATURE (°C)
1511 • TPC04
I
VA
vs
∆V
OVP
(Voltage Amplifier)
4
3
DUTY CYCLE (%)
∆V
OVP
(mV)
I
VC
(mA)
2
125°C
1
25°C
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
I
VA
(mA)
1511• TPC07
PROG Pin Characteristics
6
125°C
35
30
25
20
15
10
5
REFERENCE VOLTAGE (V)
BOOST CURRENT (mA)
I
PROG
(mA)
0
–6
0
1
2
3
V
PROG
(V)
4
5
1511 • TPC10
U W
25°C
I
CC
vs V
CC
7.0
MAXIMUM DUTY CYCLE
6.5
0°C
25°C
0.002
0.001
0
0.003
V
REF
Line Regulation
ALL TEMPERATURES
–0.001
–0.002
–0.003
4.5
0
5
10
15
V
CC
(V)
20
25
30
0
5
10
15
V
CC
(V)
20
25
30
1511 • TPC05
1511 • TPC06
Maximum Duty Cycle
98
97
96
95
94
93
92
91
90
0
20
40
60
80
100
120
140
TEMPERATURE (°C)
1511 • TPC08
V
C
Pin Characteristics
–1.20
–1.08
–0.96
–0.84
–0.72
–0.60
–0.48
–0.36
–0.24
–0.12
0
0.12
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
V
C
(V)
1511 • TPC09
Switch Current vs Boost Current
vs Boost Voltage
50
45
40
V
CC
= 16V
V
BOOST
= 38V
28V
18V
2.468
2.466
2.464
2.462
2.460
2.458
2.470
Reference Voltage
vs Temperature
0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
SWITCH CURRENT (A)
1511 • TPC11
0
25
50
75
100
TEMPERATURE
125
150
LT1511 • TPC12
5
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