LT3651-8.2/LT3651-8.4
Monolithic 4A High Voltage
2-Cell Li-Ion Battery Charger
FEATURES
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DESCRIPTION
The LT
®
3651-8.2/LT3651-8.4 are 2-cell, 4A Li-Ion/Poly-
mer battery chargers that operate over a 9V to 32V input
voltage range. An efficient monolithic average current
mode synchronous switching regulator provides constant
current, constant voltage charging with programmable
maximum charge current. A charging cycle starts with
battery insertion or when the battery voltage drops 2.5%
below the float voltage. Charger termination is selectable
as either charge current or internal safety timer timeout.
Charge current termination occurs when the charge cur-
rent falls to one-tenth the programmed maximum current
(C/10). Timer based termination is typically set to three
hours and is user programmable (charging continues
below C/10 until timeout). Once charging is terminated,
the LT3651-8.2/LT3651-8.4 supply current drops to 85µA
into a standby mode.
The LT3651-8.2/LT3651-8.4 offer several safety features.
A discharged battery is preconditioned with a small trickle
charge and generates a signal if unresponsive. A thermistor
monitors battery temperature, halting charging if out of
range. Excessive die temperature reduces charge current.
Charge current is also reduced to maintain constant input
current to prevent excessive input loading.
The LT3651-8.2/LT3651-8.4 are available in a 5mm
×
6mm 36-lead QFN package.
Wide Input Voltage Range: 9V to 32V
(40V Absolute Maximum)
Programmable Charge Current Up to 4A
Selectable C/10 or Onboard Timer Termination
Dynamic Charge Rate Programming/Soft-Start
Programmable Input Current Limit
±0.5% Float Voltage Accuracy
±7.5% Charge Current Accuracy
±4% C/10 Detection Accuracy
NTC Resistor Temperature Monitor
Auto-Recharge at 97.5% Float Voltage
Auto-Precondition at <70% Float Voltage
Bad Battery Detection with Auto-Reset
Average Current Mode, Synchronous Switcher
User Programmable Frequency
Low Profile (0.75mm) 5mm
×
6mm 36-Lead
QFN Package
APPLICATIONS
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Industrial Handheld Instruments
12V to 24V Automotive and Heavy Equipment
Desktop Cradle Chargers
Notebook Computers
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
9V to 32V 2-Cell 4A Charger
V
IN
9V TO 32V
Si7611DN
100k
10k
22µF
TO
SYSTEM
LOAD
90
Efficiency, Power Loss vs V
IN
V
BAT
= 7.8V
I
BAT
= 4A
6.0
EFFICIENCY
10V
CLP
SHDN
ACPR
FAULT
CHRG
RT
CLN
V
IN
SW
1µF
BOOST
89
EFFICIENCY (%)
5.5
POWER LOSS (W)
LT3651-8.2/LT3651-8.4
CMPSH1-4
SENSE
10µH
TDK SLP12575T-100M5R4
88
5.0
87
POWER LOSS
4.5
24m
100µF
301k
BAT
NTC
TIMER
I
LIM
RNG/SS GND
+
86
2-CELL
Li-Ion
BATTERY
365188284 TA01a
4.0
3.5
85
10
15
20
V
IN
(V)
25
30
1635 G07
36518284f
1
LT3651-8.2/LT3651-8.4
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
RNG/SS
GND
CLN
SW
CLP
28 I
LIM
27
SHDN
37
GND
26
CHRG
25
FAULT
24 TIMER
23 GND
22 SW
38
SW
21 NC
20 NC
19 NC
11 12 13 14 15 16 17 18
SW
SW
SW
SW
SW
SW
UHE PACKAGE
36-LEAD (5mm
×
6mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 37) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 38) IS SW, MUST BE SOLDERED TO PCB
SW
V
IN
V
IN
V
IN
RT
NTC 1
ACPR
2
BAT 3
SENSE 4
BOOST 5
GND 6
SW 7
NC 8
NC 9
NC 10
V
IN
.......................................................................... 40V
CLN, CLP,
SHDN, CHRG,
FAULT, ACPR
............................... V
IN
+ 0.5V Up to 40V
CLP – CLN .............................................................±0.5V
SW ...........................................................................40V
SW – V
IN
..................................................................4.5V
BOOST .......................................... SW + 10V Up to 50V
SENSE, BAT ............................................................ 10V
SENSE-BAT ............................................. –0.5V to 0.5V
TIMER, RNG/SS, I
LIM
, NTC, RT .............................. 2.5V
Operating Junction Temperature Range
(Notes 2, 3) ................................................ –40 to 125°C
Storage Temperature Range ......................–65 to 150°C
36 35 34 33 32 31 30 29
ORDER INFORMATION
LEAD FREE FINISH
LT3651EUHE-8.2#PBF
LT3651IUHE-8.2#PBF
LT3651EUHE-8.4#PBF
LT3651IUHE-8.4#PBF
TAPE AND REEL
LT3651EUHE-8.2#TRPBF
LT3651IUHE-8.2#TRPBF
LT3651EUHE-8.4#TRPBF
LT3651IUHE-8.4#TRPBF
PART MARKING*
365182
365182
365184
365184
PACKAGE DESCRIPTION
36-Lead (5mm
×
6mm) Plastic QFN
36-Lead (5mm
×
6mm) Plastic QFN
36-Lead (5mm
×
6mm) Plastic QFN
36-Lead (5mm
×
6mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container.Consult LTC Marketing for information on non-standard 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/
36518284f
2
LT3651-8.2/LT3651-8.4
ELECTRICAL CHARACTERISTICS
PARAMETER
V
IN
Operating Range
V
IN
OVLO Threshold
V
IN
OVLO Hysteresis
V
IN
UVLO Threshold
V
IN
UVLO Hysteresis
Battery Float Voltage, V
BAT(FLT)
LT3651-8.2
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 20V,
SHDN
= 2V, SENSE = BAT = V
BAT(FLT)
,
C
TIMER
= 0.68µF, R
T
= 50k, CLP = CLN = V
IN
, BOOST – SW = 4V.
CONDITIONS
l
MIN
9.0
32
l
TYP
35
1.1
8.7
0.2
MAX
32
40
9.0
8.24
8.28
8.44
8.48
UNITS
V
V
V
V
V
V
V
V
V
mV
V
V
mV
mA
µA
µA
mV
mV
mA
mA/A
mV
V
IN
Rising
V
IN
Rising
8.16
8.12
8.36
8.32
8.2
8.4
–200
5.65
5.80
90
8.6
80
17
480
–140
40
25
14
LT3651-8.4
l
Battery Recharge Voltage Hysteresis
Battery Precondition Threshold Voltage, V
BAT(PRE)
Battery Precondition Threshold Hysteresis
Operating V
IN
Supply Current
Top Switch On Voltage
Bottom Switch On Voltage
BOOST Supply Current
BOOST Switch Drive
Precondition Current Sense Voltage
Input Current Limit Voltage
CLP Input Bias Current
CLN Input Bias Current
I
LIM
Bias Current
System Current Limit Programming Gain
Maximum Charge Current Sense Voltage
C/10 Trigger Sense Voltage
BAT Input Bias Current
SENSE Input Bias Current
RNG/SS Bias Current
Charge Current Limit Programming Gain
NTC Range Limit (High)
NTC Range Limit (Low)
NTC Threshold Hysteresis
NTC Disable Impedance
NTC Bias Current
Shutdown Threshold
Shutdown Hysteresis
SHDN
Input Bias Current
Status Low Voltage
Threshold Voltage Relative to V
BAT(FLT)
LT3651-8.2, V
BAT
Rising
LT3651-8.4, V
BAT
Rising
Threshold Voltage Relative to V
BAT(PRE)
CC/CV Mode, Top Switch On, I
SW
= 0
Standby Mode
Shutdown (SHDN = 0)
V
IN
– V
SW
, I
SW
= 4A
V
SW
, I
SW
= 4A
Switch High, I
SW
= 0, 2.5V < (V
BOOST
– V
SW
) < 8.5V
I
BOOST
/I
SW
, I
SW
= 4A
V
SENSE
– V
BAT
, V
BAT
= 5.0V
V
CLP
– V
CLN
, I
LIM
Open
l
70
95
120
36
115
mV
nA
µA
l
43
88
4.5
50
11.5
95
8.6
0.1
0.1
57
103
12.3
1
1
56
12.5
1.45
0.31
µA
V/V
mV
mV
µA
µA
µA
V/V
V
V
%
kΩ
V
ILIM
/(V
CLP
– V
CLN
), V
ILIM
= 0.5V
V
SENSE
– V
BAT
, V
BAT
= 7.5V, V
RNG/SS
> 1.1V
V
SENSE
– V
BAT
Charging Terminated
Charging Terminated
l
l
l
44
8.5
1.25
0.27
150
46.5
1.15
50
10.8
1.36
0.29
10
470
50
1.20
95
–10
V
RNG/SS
/(V
SENSE
– V
BAT
), V
RNG/SS
= 0.5V
V
NTC
Rising
V
NTC
Falling
% of Threshold
Minimum External Impedance to GND
V
NTC
= 0.75V
V
SHDN
Rising
l
l
l
l
l
l
53.5
1.23
µA
V
mV
nA
V
CHRG
, V
FAULT
, V
ACPR
, Load = 10mA
l
0.45
V
36518284f
3
LT3651-8.2/LT3651-8.4
ELECTRICAL CHARACTERISTICS
PARAMETER
TIMER Charge/Discharge Current
TIMER Disable Threshold
Full Charge Cycle Time-Out
Precondition Timeout
Timer Accuracy
Switcher Operating Frequency, f
O
Minimum SW On-Time, t
ON(MIN)
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:
The LT3651-8.2/LT3651-8.4 are tested under pulse loaded
conditions such that T
J
= T
A
. The LT3651-8.2E/LT3651-8.4E are
guaranteed to meet performance specifications from 0°C to 85°C junction
temperature. Specifications over the –40°C to 125°C operating junction
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3651-8.2I/LT3651-8.4I are
guaranteed over the full –40°C to 125°C operating junction temperature
range. The junction temperature (T
J
in °C) is calculated from the ambient
temperature (T
A
in °C) and power dissipation (P
D
in Watts) according to
the formula:
T
J
= T
A
+ P
D
•
θ
JA
where
θ
JA
(in °C/W) is the package thermal impedance.
R
T
= 50kΩ
R
T
= 250kΩ
l
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 20V,
SHDN
= 2V, SENSE = BAT = V
BAT(FLT)
,
C
TIMER
= 0.68µF, R
T
= 50k, CLP = CLN = V
IN
, BOOST – SW = 4V.
CONDITIONS
MIN
0.1
TYP
25
0.25
3
22.5
–13
1.1
250
150
13
MAX
UNITS
µA
V
Hour
Minute
%
MHz
kHz
ns
Note 3:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.
36518284f
4
LT3651-8.2/LT3651-8.4
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Float Voltage
vs Temperature
1.0
100
95
0.5
∆V
BAT(FLT)
(%)
I
VIN
(µA)
90
85
CURRENT (µA)
80
75
70
65
60
55
–1.0
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
50
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
V
IN
Standby Mode Current
vs Temperature
150
100
50
0
–50
–100
–150
–200
–250
–300
–350
SENSE and BAT Pin Currents
vs BAT Voltage (V
SENSE
= V
BAT
)
LT3651-8.4
I
SENSE
I
BAT
0
–0.5
0
1
2
3
5
4
V
BAT
(V)
6
7
8
9
36518284 G01
36518284 G02
36518284 G03
C/10 Threshold (V
SENSE
– V
BAT
)
vs Temperature
11
120
100
10
V
SENSE
– V
BAT
(mV)
I
CHG(MAX)
(%)
80
60
40
20
7
–50
0
Maximum Charge Current
vs V
RNG/SS
as a Percentage
of Programmed I
IN(MAX)
101.0
I
CHG
Current Limit
(V
SENSE
– V
BAT
) vs Temperature
100.5
V
SENSE
– V
BAT
(mV)
0
0.4
0.6
V
RNG/SS
(V)
36518284 G04
36518284 G05
9
100.0
8
99.5
–25
75
0
25
50
TEMPERATURE (°C)
100
125
0.2
0.8
1.0
1.2
99.0
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
36518284 G06
Charge Current vs V
BAT
as a
Percentage of Programmed
I
CHG(MAX)
120
100
80
I
CHG
(%)
60
40
20
0
LT3651-8.4
120
100
80
60
40
20
0
Maximum Input Current
vs V
ILIM
as a Percentage
of Programmed I
IN(MAX)
I
IN(MAX)
(%)
5
6
7
V
BAT
(V)
8
9
36518284 G07
0
0.2
0.4
0.6
0.8
V
ILIM
(V)
1.0
1.2
36518284 G08
36518284f
5
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