LTC4008
4A, High Efficiency,
Multi-Chemistry Battery Charger
FEATURES
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DESCRIPTIO
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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
The LTC
®
4008 is a constant-current/constant-voltage
charger controller. The PWM controller uses a synchro-
nous, quasi-constant frequency, constant off-time archi-
tecture that will not generate audible noise even when
using ceramic capacitors. Charging current is program-
mable 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
battery temperature returns to within safe limits; a FAULT
pin indicates this condition. A FLAG pin indicates when
charging current has decreased below 10% of the pro-
grammed 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. Patents including 5723970
APPLICATIO S
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Notebook Computers
Portable Instruments
Battery Backup Systems
TYPICAL APPLICATIO
DCIN
0V TO 28V
12.3V, 4A Li-Ion Charger
INPUT SWITCH
0.1µF
140k*
V
LOGIC
100k
I
CL
ACP
FAULT
FLAG
32.4k
100k
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
U
4008fa
U
U
1
LTC4008
ABSOLUTE
MAXIMUM
RATINGS
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
PACKAGE/ORDER INFORMATION
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
ORDER PART
NUMBER
LTC4008EGN
PROG 10
GN PACKAGE
20-LEAD NARROW PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 90°C/W
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
V
TOL
PARAMETER
DCIN Operating Range
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
Charge Current Accuracy (Note 3)
The
●
denotes specifications which apply over the full operating
temperature range (Note 4), 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
●
DCIN = 0V (LTC4008 Only)
ACP/SHDN = 0V
DCIN Rising, V
BAT
= 0V
V
SHDN
= 0V, Sum of Current from CLP,
CLN, DCIN
2
U
U
W
W W
U
W
(Note 1)
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
TOP VIEW
DCIN
I
CL
SHDN
R
T
FAULT
GND
V
FB
NTC
I
TH
1
2
3
4
5
6
7
8
9
20 NC
19 BGATE
18 PGND
17 TGATE
16 CLP
15 CLN
14 FLAG
13 BATMON
12 BAT
11 CSP
ORDER PART
NUMBER
LTC4008EGN-1
PROG 10
THE LTC4008EGN-1
Does Not Have the
Input FET Function
GN PACKAGE
20-LEAD NARROW PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 90°C/W
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
●
●
●
●
4008fa
LTC4008
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
Input Bias Current Into BAT Pin
CMSL
CMSH
V
OS
I
TMAX
I
TREV
CA1/I
1
Input Common Mode Low
CA1/I
1
Input Common Mode High
Input Voltage Offset
Maximum Current Sense Threshold (V
CSP
– V
BAT
)
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
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
FLAG (C/10) Accuracy
I
CL
Threshold Accuracy
Low Logic Level of ACP/SHDN, FLAG, I
CL
, FAULT
High Logic Level of ACP/SHDN, I
CL
Off State Leakage Current of FLAG, FAULT
Pull-Up Current on ACP/SHDN, I
CL
Current Sense Amplifier, CA1
The
●
denotes specifications which apply over the full operating
temperature range (Note 4), otherwise specifications are at T
A
= 25°C. V
DCIN
= 20V, V
BAT
= 12V unless otherwise noted.
CONDITIONS
MIN
TYP
11.66
●
MAX
UNITS
µA
V
0
V
CLN
– 0.2
–3.5
3.5
165
– 30
1
200
V
DCIN
≤
28V
●
V
mV
mV
mV
mmho
µA
µA
mmho
Current Comparators I
CMP
and I
REV
V
ITH
= 2.5V
●
140
Current Sense Amplifier, CA2
Measured at I
TH
, V
ITH
= 1.4V
Measured at I
TH
, V
ITH
= 1.4V
– 40
40
1.4
●
93
100
100
1
1.19
±4
107
mV
nA
mmho
V
Voltage Error Amplifier, EA
±25
110
nA
µA
%
Measured at I
TH
, V
ITH
= 1.4V
●
36
102
107
Input P-Channel FET Driver (INFET) (LTC4008 Only)
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
Voltage Falling at PROG
V
CLP
– V
CLN
I
OL
= 100µA
I
OH
= –1µA
V
OH
= 3V
V = 0V
●
●
●
●
●
●
●
●
0
0.17
25
0.25
50
6.5
0.25
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
V
V
µA
V
mV
V
V
µA
µA
4008fa
0.375
83
2.7
–1
0.397
93
0.420
105
0.5
1
–10
3
LTC4008
ELECTRICAL CHARACTERISTICS
SYMBOL
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
PARAMETER
The
●
denotes specifications which apply over the full operating
temperature range (Note 4), otherwise specifications are at T
A
= 25°C. V
DCIN
= 20V, V
BAT
= 12V unless otherwise noted.
CONDITIONS
MIN
255
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
20
98
TYP
300
25
99
50
10
10
50
110
100
90
80
100
100
MAX
345
UNITS
kHz
kHz
%
mV
V
V
mV
ns
ns
ns
ns
mV
mV
Gate Drivers (TGATE, BGATE)
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
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.
TYPICAL PERFOR A CE CHARACTERISTICS
INFET Response Time to
Reverse Current
0.05
V
gs
OF PFET (2V/DIV)
V
gs
= 0
0
V
BATTERY
- V
BATMON
(V)
V
s
OF PFET (5V/DIV)
V
FB
(%)
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
4
U W
(T
A
= 25°C unless otherwise noted)
V
FB
vs DCIN
0.02
0
–0.02
–0.04
–0.06
–0.08
–0.10
6
11
16
21
DCIN (V)
26
4008 G02
BATMON Offset
BATMON LOAD = 100kΩ
–0.05
–0.10
–0.15
–0.20
DCIN = 15V
DCIN = 20V
DCIN = 24V
3
8
13
18
BATTERY VOLTAGE (V)
23
4008 G03
4008fa
LTC4008
TYPICAL PERFOR A CE CHARACTERISTICS
V
OUT
vs I
OUT
0
–0.5
OUTPUT VOLTAGE ERROR (%)
–1.0
PWM FREQUENCY (kHz)
–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
Battery Leakage Current vs
Battery Voltage
40
VDCIN = 0V
100
BATTERY LEAKAGE CURRENT (µA)
35
95
30
25
20
15
10
5
0
0
5
10
15
20
BATTERY VOLTAGE (V)
25
30
4008 G07
EFFICIENCY (%)
Efficiency at 12.6V with 15VDC V
IN
100
0.150
0.125
0.100
0.075
0.050
0.025
0
–0.025
–0.050
–0.075
–0.100
–0.125
–0.150
95
EFFICIENCY (%)
OUTPUT VOLTAGE ERROR (V)
90
85
80
75
0.50
1.00
1.50
2.00
2.50
CHARGE CURRENT (A)
3.00
4008 G10
U W
(T
A
= 25°C unless otherwise noted)
Disconnect/Reconnect Battery
(Load Dump)
3A STEP
1A STEP
V
FLOAT
1V/(DIV)
PWM Frequency vs Duty Cycle
350
300
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
1A STEP
LOAD
STATE
3A STEP
DISCONNECT
RECONNECT
LOAD CURRENT = 1A, 2A, 3A
DCIN = 20V
V
FLOAT
= 12.6V
4008 G06
Efficiency at 19VDC V
IN
16.8V
12.6V
90
85
80
75
0.50
1.00
1.50
2.00
2.50
CHARGE CURRENT (A)
3.00
4008 G09
Charging Voltage Error
TEMP = 27°C, I
LOAD
= 0.120A
DCIN = 20V
DCIN = 15V
0
2
4
6 8 10 12 14 16 18 20 22
CHARGING VOLTAGE (V)
4008 G11
4008fa
5
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