FEATURES
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LTC4012-3
High Efficiency,
Multi-Chemistry Battery Charger
with PowerPath Control
DESCRIPTION
The LTC4012-3 is a constant-current/constant-voltage
battery charger controller. It uses a synchronous quasi-
constant frequency PWM control architecture that will not
generate audible noise with ceramic bulk capacitors. Charge
current is set by external resistors and can be monitored
as an output voltage across the programming resistor.
With no built-in termination, the LTC4012-3 charges a
wide range of batteries under external control.
The LTC4012-3 features fully adjustable output voltage. For
charge management and safety, the IC includes an input
P-channel MOSFET ideal diode controller, battery (output)
overvoltage protection, reverse charge current protection,
PWM soft-start and robust non-overlap control for an all
N-channel MOSFET PWM power stage.
The device includes AC adapter input current limiting, which
maximizes the charge rate for a fixed input power level. An
external sense resistor programs the input current limit,
and the
ICL
status pin indicates reduced charge current as
a result of AC adapter current limiting. Ideal diode control
at the adaptor input improves charger efficiency.
The
CHRG
status pin is active during all charging modes,
including special indication for low charge current.
General Purpose Battery Charger Controller
Efficient 550kHz Synchronous Buck PWM Topology
±0.5% Output Float Voltage Accuracy
Programmable Charge Current: 4% Accuracy
Programmable AC Adapter Current Limit:
3% Accuracy
No Audible Noise with Ceramic Capacitors
INFET Low Loss Ideal Diode PowerPath™ Control
Wide Input Voltage Range: 6V to 28V
Wide Output Voltage Range: 2V to 28V
Indicator Outputs for Charging, C/10 Current
Detection and Input Current Limiting
Analog Charge Current Monitor
Micropower Shutdown
20-Pin 4mm
×
4mm
×
0.75mm QFN Package
APPLICATIONS
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Notebook Computers
Portable Instruments
Battery Backup Systems
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation. PowerPath
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Protected by U.S. Patents including 5723970.
TYPICAL APPLICATION
FROM
ADAPTER
13V TO 20V
INFET
DCIN
0.1μF
CLP
CLN
BOOST
TGATE
SW
INTV
DD
BGATE
GND
3.01k
ITH
6.04k
0.1μF
CSP
25mΩ
0.1μF
5.1k
20μF
POWER TO
SYSTEM
Efficiency at DCIN = 20V
100
95
EFFICIENCY (%)
EFFICIENCY
POWER LOSS (mW)
10000
0.1μF
90
85
80
75
70
V
OUT
= 12.3V
R
SENSE
= 33mΩ
R
IN
= 3.01k
R
PROG
= 26.7k
0
0.5
1
1.5
2
CHARGE CURRENT (A)
PIN J NAME
ACP
X
4012-3 TA02
POWER LOSS
1000
CHRG
TO/FROM
MCU
ICL
SHDN
2μF
6.8μH
LTC4012-3
CSN
PROG
BAT
FBDIV
33mΩ
3.01k
2.5
3
100
20μF
301k
26.7k
4.7nF
+
V
FB
32.8k
12.3V
Li-Ion
BATTERY
4012-3 TA01
PART
GND
LTC4012
LTC4012-3
X
40123f
1
LTC4012-3
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
INTV
DD
BOOST
BGATE
15 CSP
14 CSN
21
13 PROG
12 ITH
11 BAT
6
SHDN
7
CHRG
8
ICL
9 10
FBDIV
V
FB
TGATE
SW
DCIN ........................................................... –14V to 30V
DCIN to CLP ................................................ –32V to 20V
CLP CLN or SW to GND ............................. –0.3V to 30V
,
CLP to CLN ............................................................±0.3V
CSP CSN or BAT to GND ............................ –0.3V to 28V
,
CSP to CSN ............................................................±0.3V
BOOST to GND ........................................... –0.3V to 36V
BOOST to SW............................................... –0.3V to 7V
SHDN
or V
FB
to GND .................................... –0.3V to 7V
CHRG
or
ICL
to GND .................................. –0.3V to 30V
Operating Temperature Range
(Note 2)........................................................ 0°C to 85°C
Junction Temperature (Note 3) ............................. 125°C
Storage Temperature Range...................–65°C to 150°C
20 19 18 17 16
CLN 1
CLP 2
INFET 3
DCIN 4
GND 5
UF PACKAGE
20-LEAD (4mm 4mm) PLASTIC QFN
T
JMAX
= 125°C,
JA
= 37°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4012CUF-3#PBF
TAPE AND REEL
LTC4012CUF-3#TRPBF
PART MARKING
40123
PACKAGE DESCRIPTION
20-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
0°C to 85°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/
40123f
2
LTC4012-3
ELECTRICAL CHARACTERISTICS
SYMBOL
V
TOL
I
VFB
R
ON
I
LEAK-FBDIV
V
BOV
I
TOL
PARAMETER
V
BAT
Accuracy (See Test Circuits)
V
FB
Input Bias Current
FBDIV On Resistance
FBDIV Output Leakage Current
V
FB
Overvoltage Threshold
Charge Current Accuracy with R
IN
= 3.01k,
5V < BAT < 18V
Current Sense Amplifier Gain (PROG ΔI) with
R
IN
= 3.01k, 5V < BAT < 18V
Maximum Peak Current Sense Threshold Voltage
per Cycle (R
IN
= 3.01k)
C/10 Indicator Threshold Voltage
Reverse Current Threshold Voltage
Current Limit Threshold
CLN Input Bias Current
ICL
Indicator Threshold
Operating Voltage Range
CLP Undervoltage Lockout Threshold
UVLO Threshold Hysteresis
CLP Operating Current
SHDN
Input Voltage Low
SHDN
Input Voltage High
SHDN
Pull-Down Resistance
CLP Shutdown Current
BAT Leakage Current
CSN Leakage Current
CSP Leakage Current
SW Leakage Current
CLP = 12V, DCIN = 0V
SHDN
= 0V
SHDN
= 0V or DCIN = 0V,
0V ≤ CSP = CSN = BAT ≤ 18V
SHDN
= 0V or DCIN = 0V,
0V ≤ CSP = CSN = BAT ≤ 20V
SHDN
= 0V or DCIN = 0V,
0V ≤ CSP = CSN = BAT ≤ 20V
SHDN
= 0V or DCIN = 0V,
0V ≤ SW ≤ 20V
No Load
I
DD
= 20mA
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. DCIN = 20V, BAT = 12V, GND = 0V unless otherwise noted.
CONDITIONS
MIN
–0.5
–0.8
±20
l
l
l
TYP
MAX
0.5
0.8
UNITS
%
%
nA
Ω
μA
V
%
%
μA
μA
mV
mV
mV
mV
mV
mV
nA
mV
V
V
mV
mA
mV
V
kΩ
Charge Voltage Regulation
l
V
FB
= 1.2V
I
LOAD
= 100μA
SHDN
= 0V, FBDIV = 0V
–1
1.235
–4
–5
–12.75
–1.78
l
l
85
0
1.281
190
1
1.32
4
5
Charge Current Regulation
R
PROG
= 26.7k
V
SENSE
= 0mV, PROG = 1.2V
A
I
V
CS-MAX
V
C10
V
REV
V
CL
I
CLN
V
ICL
CLP Supply
OVR
V
UVLO
V
UV(HYST)
I
CLPO
Shutdown
V
IL
V
IH
R
IN
I
CLPS
I
LEAK-BAT
I
LEAK-CSN
I
LEAK-CSP
I
LEAK-SW
l
l
l
–11.67
–1.66
185
325
400
253
100
100
±100
–5
–10.95
–1.54
235
430
460
295
103
104
–2
28
V
SENSE
Step from 0mV to 5mV,
PROG = 1.2V
ITH = 2V
ITH = 5V
PROG Falling
PROG Falling
CLP – CLN
CLN = CLP
(CLP – CLN) – V
CL
140
340
180
97
96
–8
6
Input Current Regulation
l
CLP Increasing
CLP = 20V, No Gate Loads
l
4.65
4.835
200
2
5.15
3
300
1.4
40
15
350
–1
–1
–1
–1
0
0
0
0
25
500
1
1
1
2
μA
μA
μA
μA
μA
μA
INTV
DD
Regulator
INTV
DD
ΔV
DD
Output Voltage
Load Regulation
l
4.85
5
–0.4
5.15
–1
V
%
40123f
3
LTC4012-3
ELECTRICAL CHARACTERISTICS
SYMBOL
I
DD
V
ACP
I
ITH
f
TYP
f
MIN
DC
MAX
t
R-TG
t
F-TG
t
R-BG
t
F-BG
t
NO
I
DCIN
V
FTO
V
FR
V
RTO
V
OL(INFET)
V
OH(INFET)
t
IF(ON)
t
IF(OFF)
V
OL
I
LEAK
I
C10
PARAMETER
Short-Circuit Current (Note 5)
AC Present Charge Enable Threshold Voltage
I
TH
Current
Typical Switching Frequency
Minimum Switching Frequency
Maximum Duty Cycle
TGATE Rise Time
TGATE Fall Time
BGATE Rise Time
BGATE Fall Time
TGATE, BGATE Non-Overlap Time
DCIN Input Current
Forward Turn-on Voltage (DCIN Detection Threshold)
Forward Regulation Voltage
Reverse Turn-Off Voltage
INFET Output Low Voltage, Relative to CLP
INFET Output High Voltage, Relative to CLP
INFET Turn-On Time
INFET Turn-Off Time
Output Voltage Low
Output Leakage
CHRG
C/10 Current Sink
C
LOAD
= 3.3nF
C
LOAD
= 3.3nF
C
LOAD
= 3.3nF, 10% – 90%
C
LOAD
= 3.3nF, 90% – 10%
C
LOAD
= 3.3nF, 10% – 90%
C
LOAD
= 3.3nF, 90% – 10%
C
LOAD
= 3.3nF, 10% – 10%
0V ≤ DCIN ≤ CLP
DCIN-CLP, DCIN rising
DCIN-CLP
DCIN-CLP DCIN falling
,
DCIN-CLP = 0.1V, I
INFET
=1μA
DCIN-CLP = –0.1V, I
INFET
=–5μA
To CLP-INFET > 3V, C
INFET
= 1nF
To CLP-INFET < 1.5V, C
INFET
= 1nF
I
LOAD
= 100μA, PROG = 1.2V
SHDN
= 0V, DCIN = 0V, V
OUT
= 20V
CHRG
= 2.5V
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. DCIN = 20V, BAT = 12V, GND = 0V unless otherwise noted.
CONDITIONS
INTV
DD
= 0V
DCIN – BAT, DCIN Rising
I
TH
= 1.4V
467
20
98
l
MIN
50
350
TYP
85
500
–40/+90
550
25
99
60
50
60
60
110
MAX
120
600
633
UNITS
mA
mV
μA
kHz
kHz
%
Switching Regulator
110
110
110
110
ns
ns
ns
ns
ns
PowerPath Control
–10
15
15
–45
–6.5
–250
85
2.5
25
–25
60
60
35
–15
–5
250
180
6
500
–10
15
25
10
38
μA
mV
mV
mV
V
mV
μs
μs
mV
μA
μA
Indicator Outputs
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 LTC4012-3 is guaranteed to meet performance specifications
over the 0°C to 85°C operating temperature range.
Note 3:
Operating junction temperature T
J
(in °C) is calculated from
the ambient temperature T
A
and the total continuous package power
dissipation P
D
(in watts) by the formula T
J
= T
A
+ (θ
JA
• PD). Refer to the
Applications Information section for details.
Note 4:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to GND, unless otherwise
specified.
Note 5:
Output current may be limited by internal power dissipation. Refer
to the Applications Information section for details.
40123f
4
LTC4012-3
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C unless otherwise noted. L = IHLP-2525 6.8μH)
Efficiency at DCIN = 20V, BAT = 8V
100
R
SENSE
= 33mΩ
R
IN
= 3.01k
95
POWER LOSS(mW)
EFFICIENCY (%)
EFFICIENCY
90
POWER LOSS
1000
EFFICIENCY (%)
95
10000
100
R
SENSE
= 33mΩ
R
IN
= 3.01k
EFFICIENCY
POWER LOSS(mW)
Efficiency at DCIN = 20V, BAT = 12V
10000
90
POWER LOSS
1000
85
85
80
0
0.5
1
1.5
2
CHARGE CURRENT (A)
2.5
3
100
80
0
0.5
1
1.5
2
CHARGE CURRENT (A)
2.5
3
100
4012-3 G01
4012-3 G02
Efficiency at DCIN = 20V, BAT = 16V
100
EFFICIENCY
95
POWER LOSS(mW)
EFFICIENCY (%)
V
FB
ERROR (%)
10000
0.10
0.08
0.06
0.04
0.02
0
–0.02
–0.04
–0.06
–0.08
3
100
–0.10
V
FB
Line Regulation
LTC4012-3 TEST CIRCUIT
90
POWER LOSS
1000
85
R
SENSE
= 33mΩ
R
IN
= 3.01k
80
0
0.5
1
1.5
2
CHARGE CURRENT (A)
2.5
5
10
20
15
CLP (V)
25
30
4012-3 G04
4012-3 G03
FBDIV Pin R
ON
vs Battery Voltage
300
275
250
225
R
ON
(Ω)
200
175
150
125
100
75
0
5
15
10
BAT (V)
20
25
4012-3 G05
Battery Load Dump
BATTERY VOLTAGE
(500mV/DIV)
2A
12.1V
1A
3A
RECONNECT
DISCONNECT
TIME (1ms/DIV)
CLP = 20V
V
FLOAT
= 12.3V
4012-3 G06
CLP = BAT + 3V
(CLP ≥ 6V)
1A
LOAD
STATE
40123f
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