LTC4008
4A, High Efficiency,
Multi-Chemistry Battery Charger
FEATURES
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DESCRIPTION
The LTC
®
4008 is a constant-current/constant-voltage
charger controller. The PWM controller uses a synchronous,
quasi-constant frequency, constant off-time architecture
that will not generate audible noise even when using ceramic
capacitors. Charging current is programmable with a sense
resistor and programming resistor to ±4% typical accuracy.
Charging current can be monitored as a voltage across
the programming resistor. An external resistor divider and
precision internal reference set the final float voltage.
The LTC4008 includes a thermistor sensor input that will
suspend charging if an unsafe temperature condition is
detected and will automatically resume charging when bat-
tery temperature returns to within safe limits; a
FAULT
pin
indicates this condition. A
FLAG
pin indicates when charg-
ing current has decreased below 10% of the programmed
current. An external sense resistor programs AC adapter
current limiting. The I
CL
pin indicates when the charging
current is being reduced by input current limiting so that
the charging algorithm can adapt.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and No R
SENSE
are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5723970.
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General Purpose Charger Controller
High Conversion Efficiency: Up to 96%
Output Currents Exceeding 4A
±0.8% Voltage Accuracy
AC Adapter Current Limiting Maximizes
Charge Rate*
Thermistor Input for Temperature Qualified Charging
Wide Input Voltage Range: 6V to 28V
Wide Output Voltage: 3V to 28V
0.5V Dropout Voltage; Maximum Duty Cycle: 98%
Programmable Charge Current: ±4% Accuracy
Indicator Outputs for Charging, C/10 Current
Detection, AC Adapter Present, Input Current
Limiting and Faults
Charging Current Monitor Output
Available in a 20-Pin Narrow SSOP Package
APPLICATIONS
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Notebook Computers
Portable Instruments
Battery Backup Systems
TYPICAL APPLICATION
DCIN
0V TO 28V
140k*
V
LOGIC
100k
I
CL
ACP
FAULT
FLAG
32.4k
100k
12.3V, 4A Li-Ion Charger
INPUT SWITCH
0.1μF
LTC4008
BATMON
DCIN
V
FB
I
CL
ACP/SHDN
FAULT
FLAG
NTC
R
T
INFET
CLP
CLN
TGATE
BGATE
PGND
CSP
BAT
PROG
3.01k
3.01k
CHARGING
CURRENT
MONITOR
Q2
20μF
Li-Ion
BATTERY
Q1
0.1μF
4.99k
20μF
10μH
0.025Ω
0.02Ω
SYSTEM
LOAD
15k*
THERMISTOR
10k
NTC
150k
0.47μF
6.04k
0.12μF
I
TH
GND
0.0047μF
26.7k
Q1: Si4431BDY
Q2: FDC645N
4008 TA01
NOTE: * 0.25% TOLERANCE
ALL OTHER RESISTORS ARE 1% TOLERANCE
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LTC4008
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Voltage from DCIN, CLP CLN to GND.......... +32V/–0.3 V
,
PGND with Respect to GND ...................................±0.3V
CSP BAT to GND .......................................... +28V/–0.3V
,
V
FB
, R
T
to GND ............................................... +7V/–0.3V
NTC .............................................................. +10V/–0.3V
ACP/SHDN,
FLAG, FAULT,
I
CL
..................... +32V/–0.3V
CLP to CLN ..........................................................+0.5V
Operating Ambient Temperature Range
(Note 4) ............................................... –40°C to 85°C
Operating Junction Temperature ............ –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
PIN CONFIGURATION
LTC4008
TOP VIEW
DCIN
I
CL
ACP/SHDN
R
T
FAULT
GND
V
FB
NTC
I
TH
1
2
3
4
5
6
7
8
9
20 INFET
19 BGATE
18 PGND
17 TGATE
16 CLP
15 CLN
14
FLAG
13 BATMON
12 BAT
11 CSP
DCIN
I
CL
SHDN
R
T
FAULT
GND
V
FB
NTC
I
TH
1
2
3
4
5
6
7
8
9
LTC4008-1*
TOP VIEW
20 NC
19 BGATE
18 PGND
17 TGATE
16 CLP
15 CLN
14
FLAG
13 BATMON
12 BAT
11 CSP
PROG 10
PROG 10
GN PACKAGE
20-LEAD NARROW PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
EXPOSED PAD (PIN #) IS GND, MUST BE SOLDERED TO PCB
*The LTC4008EGN-1 does not have the Input FET function
GN PACKAGE
20-LEAD NARROW PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 140°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC4008EGN#PBF
LTC4008EGN-1#PBF
TAPE AND REEL
LTC4008EGN#TRPBF
LTC4008EGN-1#TRPBF
PART MARKING
LTC4008EGN
LTC4008EGN-1
PACKAGE DESCRIPTION
20-Lead Narrow Plastic SSOP
20-Lead Narrow Plastic SSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
4008fb
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LTC4008
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
DCIN Operating Range
I
Q
V
TOL
Operating Current
Voltage Accuracy
BATMON Error (Note 5)
I
TOL
Shutdown
Battery Leakage Current
UVLO
Undervoltage Lockout Threshold
Shutdown Threshold at ACP/SHDN
Operating Current in Shutdown
Current Sense Amplifier, CA1
Input Bias Current Into BAT Pin
CMSL
CMSH
CA1/I
1
Input Common Mode Low
CA1/I
1
Input Common Mode High
V
DCIN
≤ 28V
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The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DCIN
= 20V, V
BAT
= 12V unless otherwise noted.
CONDITIONS
Charging Sum of Current from CLP CLN, DCIN
,
(Notes 2, 5)
Measured from BAT to BATMON,
R
LOAD
= 100k
V
CSP
– V
BAT
Target = 100mV
l
l
l
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l
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MIN
6
TYP
3
MAX
28
5
0.8
1.0
UNITS
V
mA
%
%
mV
%
%
μA
μA
V
V
mA
–0.8
–1.0
0
–4
–5
20
–10
4.2
1
4.7
1.6
2
35
80
4
5
35
10
5.5
2.5
3
Charge Current Accuracy (Note 3)
DCIN = 0V (LTC4008 Only)
ACP/SHDN = 0V
DCIN Rising, V
BAT
= 0V
,
V
SHDN
= 0V, Sum of Current from CLP
CLN, DCIN
11.66
0
V
CLN
– 0.2
–3.5
l
μA
V
V
mV
mV
mV
mmho
μA
μA
mmho
107
mV
nA
mmho
V
±25
110
nA
μA
%
3.5
Input Voltage Offset
V
OS
Current Comparators I
CMP
and I
REV
I
TMAX
Maximum Current Sense Threshold (V
CSP
– V
BAT
) V
ITH
= 2.5V
I
TREV
Reverse Current Threshold (V
CSP
– V
BAT
)
Transconductance
Source Current
Sink Current
Current Limit Amplifier
Transconductance
V
CLP
I
CLN
Current Limit Threshold
CLN Input Bias Current
Transconductance
V
REF
I
BEA
OVSD
Reference Voltage Used to Calculate V
FLOAT
Input Bias Current
Sink Current
Overvoltage Shutdown Threshold as a Percent of
Programmed Charger Voltage
Measured at I
TH
, V
ITH
= 1.4V
Measured at I
TH
, V
ITH
= 1.4V
Measured at I
TH
, V
ITH
= 1.4V
Current Sense Amplifier, CA2
140
165
–30
1
–40
40
1.4
200
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93
100
100
1
1.19
±4
36
Voltage Error Amplifier, EA
l
102
107
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LTC4008
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
Input P-Channel FET Driver (INFET) (LTC4008 Only)
DCIN Detection Threshold (V
DCIN
– V
CLP
)
Forward Regulation Voltage (V
DCIN
– V
CLP
)
Reverse Voltage Turn-Off Voltage (V
DCIN
– V
CLP
)
INFET “On” Clamping Voltage (V
CLP
– V
INFET
)
INFET “Off” Clamping Voltage (V
CLP
– V
INFET
)
Thermistor
NTCVR
Reference Voltage During Sample Time
High Threshold
Low Threshold
Thermistor Disable Current
Indicator Outputs (ACP/SHDN,
FLAG,
I
CL
,
FAULT
C10TOL
V
OL
V
OH
I
OFF
I
PO
Oscillator
f
OSC
f
MIN
DC
MAX
Regulator Switching Frequency
Regulator Switching Frequency in Drop Out
Regulator Maximum Duty Cycle
V
TGATE
High (V
CLP
– V
TGATE
)
V
BGATE
High
V
TGATE
Low (V
CLP
– V
TGATE
)
V
BGATE
Low
TGTR
TGTF
BGTR
BGTF
TGATE Transition Time
TGATE Rise Time
TGATE Fall Time
BGATE Transition Time
BGATE Rise Time
BGATE Fall Time
V
TGATE
at Shutdown (V
CLP
– V
TGATE
)
V
BGATE
at Shutdown
Duty Cycle ≥ 98%
V
CSP
= V
BAT
I
TGATE
= –1mA
C
LOAD
= 3000pF
C
LOAD
= 3000pF
I
BGATE
= 1mA
C
LOAD
= 3000pF 10% to 90%
,
C
LOAD
= 3000pF 10% to 90%
,
C
LOAD
= 3000pF 10% to 90%
,
C
LOAD
= 3000pF 10% to 90%
,
I
TGATE
= –1μA, DCIN = 0V, CLP = 12V
I
BGATE
= 1μA, DCIN = 0V, CLP = 12V
50
50
40
40
5.6
5.6
255
20
98
300
25
99
50
10
10
50
110
100
90
80
100
100
345
kHz
kHz
%
mV
V
V
mV
ns
ns
ns
ns
mV
mV
FLAG
(C/10) Accuracy
I
CL
Threshold Accuracy
High Logic Level of ACP/SHDN, I
CL
Off State Leakage Current of
FLAG, FAULT
Pull-Up Current on ACP/SHDN, I
CL
Voltage Falling at PROG
V
CLP
– V
CLN
I
OH
= –1μA
V
OH
= 3V
V = 0V
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l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DCIN
= 20V, V
BAT
= 12V unless otherwise noted.
CONDITIONS
DCIN Voltage Ramping Up
from V
CLP
– 0.1V
DCIN Voltage Ramping Down
I
INFET
= 1μA
I
INFET
= –25μA
4.5
V
NTC
Rising
V
NTC
Falling
V
NTC
≤ 10V
0.375
83
2.7
–1
–10
1
0.397
93
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MIN
0
TYP
0.17
25
MAX
0.25
50
6.5
0.25
UNITS
V
mV
mV
V
V
V
–60
5
–25
5.8
NTCVR
• 0.48
NTCVR
• 0.115
NTCVR
• 0.5
NTCVR
• 0.125
NTCVR
• 0.52
NTCVR
• 0.135
10
0.420
105
0.5
V
V
μA
V
mV
V
V
μA
μA
Low Logic Level of ACP/SHDN,
FLAG,
I
CL
,
FAULT
I
OL
= 100μA
Gate Drivers (TGATE, BGATE)
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:
See Test Circuit.
Note 3:
Does not include tolerance of current sense resistor or current
programming resistor.
Note 4:
The LTC4008E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 5:
Voltage accuracy includes BATMON error and voltage reference
error. Does not include error of external resistor divider.
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LTC4008
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C unless otherwise noted)
INFET Response Time to
Reverse Current
V
gs
OF PFET (2V/DIV)
V
gs
= 0
0
0.05
V
FB
vs DCIN
V
FB
(%)
V
s
OF PFET (5V/DIV)
–0.05
–0.10
V
s
= 0V
I
d
(REVERSE) OF
PFET (5A/DIV)
I
d
= 0A
1.25μs/DIV
TEST PERFORMED ON DEMOBOARD
V
CHARGE
= 12.6V
V
IN
= 15VDC
CHARGER = ON
INFET = 1/2 Si4925DY
I
CHARGE
= <10mA
4008 G01
–0.15
–0.20
6
11
16
21
DCIN (V)
26
4008 G02
BATMON Offset
0.02
0
V
BATTERY
- V
BATMON
(V)
–0.02
–0.04
–0.06
–0.08
–0.10
3
DCIN = 15V
DCIN = 20V
DCIN = 24V
8
13
18
BATTERY VOLTAGE (V)
23
4008 G03
V
OUT
vs I
OUT
0
–0.5
OUTPUT VOLTAGE ERROR (%)
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
–4.5 DCIN = 20V
V
BAT
= 12.6V
–5.0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
OUTPUT CURRENT (A)
4008 G04
BATMON LOAD = 100kΩ
PWM Frequency vs Duty Cycle
350
300
PWM FREQUENCY (kHz)
250
200
150
PROGRAMMED CURRENT = 10%
100
50
0
0
DCIN = 15V
DCIN = 20V
DCIN = 24V
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
DUTY CYCLE (V
OUT
/V
IN
)
4008 G05
Disconnect/Reconnect Battery
(Load Dump)
3A STEP
1A STEP
V
FLOAT
1V/(DIV)
1A STEP
LOAD
STATE
3A STEP
DISCONNECT
RECONNECT
LOAD CURRENT = 1A, 2A, 3A
DCIN = 20V
V
FLOAT
= 12.6V
4008 G06
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