LTC4080EMSE-PBF [Linear]
500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck; 500毫安独立锂离子电池充电器，带有集成300毫安同步降压
| 型号： | LTC4080EMSE-PBF |
| 厂家： | 
Linear |
| 描述： | 500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck |
| 文件： | 总20页 (文件大小：252K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4080
500mA Standalone Li-Ion
Charger with Integrated
300mA Synchronous Buck
U
DESCRIPTIO
FEATURES
■
Complete Linear Battery Charger with Integrated
The LTC4080 is a complete constant-current/constant-
voltage linear battery charger for a single-cell 4.2V
lithium-ion battery with an integrated 300mA synchron-
ous buck converter. The small packages and low external
componentcountmaketheLTC4080especiallysuitablefor
portableapplications.Furthermore,LTC4080isspecifically
designed to work within USB power specifications.
Buck Converter
Battery Charger:
■
Constant-Current/Constant-Voltage Operation
with Thermal Feedback to Maximize Charge Rate
Without Risk of Overheating
■
Internal 4.5 Hour Safety Timer for Termination
■
Charge Current Programmable Up to 500mA with
⎯
⎯
⎯
⎯
The CHRG pin indicates when charge current has
dropped to ten percent of its programmed value (C/10).
An internal 4.5 hour timer terminates the charge cycle.
The full-featured LTC4080 battery charger also includes
trickle charge, automatic recharge and soft-start (to limit
inrush current).
5% Accuracy
■
C/10 Charge Current Detection Output
■
5μA Supply Current in Shutdown Mode
Switching Regulator:
■
High Efficiency Synchronous Buck Converter
■
300mA Output Current
■
■
■
The LTC4080 integrates a synchronous buck converter
that is powered from the BAT pin. It has an adjustable
output voltage and can deliver up to 300mA of load cur-
rent. The buck converter also features low-current high-
efficiency Burst Mode operation that can be selected by
the MODE pin.
2.7V to 4.5V Input Range (Powered from BAT Pin)
0.8V to V Output Range
BAT
MODE Pin Selects Fixed (2.25MHz) Constant-Frequency
PWM Mode or Low I (23μA) Burst Mode®
CC
Operation
2μA BAT Current in Shutdown Mode
■
U
The LTC4080 is available in 10-lead, low profile (0.75 mm)
APPLICATIO S
3mm × 3mm DFN and MSOP Exposed Pad packages.
■
Wireless Headsets
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6522118.
■
Bluetooth Applications
■
Portable MP3 Players
■
Multifunction Wristwatches
U
Buck Efficiency vs Load Current
(VOUT = 1.8V)
TYPICAL APPLICATIO
Li-Ion Battery Charger with 1.8V Buck Regulator
100
80
60
40
20
0
1000
100
10
500mA
EFFICIENCY
(Burst)
V
CC
V
BAT
CC
4.2V
EFFICIENCY
(PWM)
(3.75V
to 5.5V)
+
BAT
LTC4080
C
L1, 1OμH
Li-Ion
POWER
LOSS
4.7μF
BATTERY
EN_CHRG
SW
FB
(PWM)
R1
1M
C
C
PL
10pF
IN
4.7μF
EN_BUCK
0
V
OUT
(1.8V/300mA)
POWER LOSS
(Burst)
MODE GND PROG
C
V
V
= 3.8V
= 1.8V
OUT
4.7μF
BAT
OUT
R
R2
806k
0.1
0.01
PROG
806Ω
L = 10μH
C = 4.7μF
4080 TA01a
0.01
0.1
1
10
100
1000
LOAD CURRENT (mA)
4080 TA01b
4080fb
1
LTC4080
W W U W
ABSOLUTE AXI U RATI GS (Note 1)
V , t < 1ms and Duty Cycle < 1%.............. – 0.3V to 7V
BAT Pin Current ...................................................800mA
PROG Pin Current....................................................2mA
Junction Temperature ...........................................125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range.................. – 65°C to 125°C
Lead Temperature (MSE, Soldering, 10 sec)......... 300°C
CC
V
Steady State......................................... – 0.3V to 6V
CC
⎯
⎯
⎯
⎯
BAT, CHRG.................................................. – 0.3V to 6V
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
EN_CHRG, PROG, ACPR.................– 0.3V to V + 0.3V
CC
BAT
MODE, EN_BUCK.......................... – 0.3V to V + 0.3V
FB ............................................................... – 0.3V to 2V
BAT Short-Circuit Duration............................Continuous
PIN CONFIGURATION
TOP VIEW
TOP VIEW
BAT
1
2
3
4
5
10 SW
BAT
CC
1
2
3
4
5
10 SW
V
CC
9
8
7
6
EN_BUCK
V
9
8
7
6
EN_BUCK
11
EN_CHRG
PROG
11
MODE
FB
CHRG
EN_CHRG
PROG
MODE
FB
ACPR
ACPR
CHRG
MSE PACKAGE
10-LEAD PLASTIC MSOP
= 125°C, θ = 40°C/W
JA
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
DD PACKAGE
T
JMAX
10-LEAD (3mm × 3mm) PLASTIC DFN
T
= 110°C, θ = 43°C/W (NOTE 3)
JA
JMAX
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4080EDD#PBF
LTC4080EMSE#PBF
TAPE AND REEL
PART MARKING
LBXD
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4080EDD#TRPBF
LTC4080EMSE#TRPBF
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
–40°C to 85°C
–40°C to 85°C
LTCQH
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/
ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at TA = 25°C, VCC = 5V, VBAT = 3.8V, VEN_CHRG = 0V, VEN_BUCK = VBAT, VMODE = 0V. (Note 2)
⎯
⎯
⎯
⎯
⎯
⎯
⎯
SYMBOL
PARAMETER
CONDITIONS
(Note 4)
MIN
3.75
2.7
TYP
5
MAX
5.5
UNITS
●
●
V
V
Supply Voltage
V
V
CC
Input Voltage for the Switching
Regulator
(Note 5)
3.8
4.5
BAT
●
●
I
I
Quiescent Supply Current (Charger On,
Switching Regulator Off)
V
V
= 4.5V (Forces I and I = 0),
PROG
EN_BUCK
110
300
10
μA
CC
BAT
BAT
= 0
Supply Current in Shutdown (Both
Battery Charger and Switching
Regulator Off)
V
= 5V, V
= 4V, V
⎯ ⎯ ⎯ ⎯ ⎯ ⎯
= 0, V > V
BAT
5
2
μA
μA
⎯
⎯
⎯
⎯
⎯
⎯
⎯
CC_SD
EN_CHRG
EN_BUCK
EN_BUCK
CC
V
= 0, V (3.5V) <
⎯
EN_CHRG
CC
V
(4V)
BAT
●
I
Battery Current in Shutdown (Both
Battery Charger and Switching
Regulator Off)
V
= 5V, V
= 4V, V
⎯ ⎯ ⎯ ⎯ ⎯ ⎯
= 0, V > V
BAT
0.6
2
5
μA
μA
⎯
⎯
⎯
⎯
⎯
⎯
⎯
BAT_SD
EN_CHRG
EN_BUCK
EN_BUCK
CC
V
= 0, V (3.5V) <
CC
⎯
EN_CHRG
V
(4V)
BAT
4080fb
2
LTC4080
ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at TA = 25°C, VCC = 5V, VBAT = 3.8V, VEN_CHRG = 0V, VEN_BUCK = VBAT, VMODE = 0V. (Note 2)
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Charger
V
V
BAT
Regulated Output Voltage
I
I
= 2mA
4.179
4.158
4.2
4.2
4.221
4.242
V
V
FLOAT
BAT
BAT
= 2mA, 4.3V < V < 5.5V
●
CC
●
●
I
Current Mode Charge Current
Undervoltage Lockout Voltage
R
R
= 4k; Current Mode; V
= 0
EN_BUCK
90
100
500
110
525
mA
mA
BAT
PROG
PROG
EN_BUCK
= 0.8k; Current Mode; V
= 0
475
●
●
V
V
V
CC
V
V
Rising
Falling
3.5
2.8
3.6
3.0
3.7
3.2
V
V
UVLO_CHRG
PROG
CC
CC
●
PROG Pin Servo Voltage
0.8k ≤ R
≤ 4k
0.98
1.0
1.02
V
PROG
V
ASD
Automatic Shutdown Threshold Voltage (V – V ), V Low to High
60
15
82
32
100
45
mV
mV
CC
BAT
CC
(V – V ), V High to Low
CC
BAT
CC
t
I
Battery Charger Soft-Start Time
Trickle Charge Current
180
50
μs
mA
V
SS_CHRG
V
V
= 2V, R
Rising
= 0.8k
35
65
TRKL
BAT
PROG
●
V
Trickle Charge Threshold Voltage
2.75
100
2.9
150
3.05
350
TRKL
BAT
V
Trickle Charge Threshold Voltage
Hysteresis
mV
TRHYS
ΔV
Recharge Battery Threshold Voltage
V
FLOAT
– V , 0°C < T < 85°C
70
100
130
mV
RECHRG
BAT
A
ΔV
UVCL1,
ΔV
UVCL2
(V – V ) Undervoltage Current
I
I
= 0.9 I
= 0.1 I
180
90
300
130
mV
mV
CC
BAT
BAT
BAT
CHG
CHG
Limit Threshold Voltage
●
●
●
●
t
Termination Timer
3
4.5
2.25
1.125
0.1
6
3
hrs
hrs
TIMER
Recharge Time
1.5
Low-Battery Charge Time
End of Charge Indication Current Level
V
= 2.5V
0.75
0.085
1.5
0.115
hrs
BAT
I
R
= 2k (Note 6)
mA/mA
°C
C/10
PROG
T
Junction Temperature in Constant-
Temperature Mode
115
LIM
R
Power FET On-Resistance (Between
CC
I
= 350mA, V = 4V
750
2
mΩ
Hz
ON_CHRG
BADBAT
BAT
CC
V
and BAT)
⎯ ⎯ ⎯ ⎯
Defective Battery Detection CHRG Pulse V = 2V
Frequency
f
BAT
⎯ ⎯ ⎯ ⎯
Defective Battery Detection CHRG Pulse V = 2V
D
75
%
BADBAT
BAT
Frequency Duty Ratio
Buck Converter
●
●
V
FB Servo Voltage
0.78
–50
1.8
0.80
0.82
50
V
nA
FB
I
f
I
FB Pin Input Current
Switching Frequency
V = 0.85V
FB
FB
2.25
1.9
2.75
MHz
mA
OSC
No-Load Battery Current (Continuous
Frequency Mode)
No-Load for Regulator, V
L = 10μH, C = 4.7μF
= 5V,
= 5V,
⎯
⎯
⎯
⎯
⎯
⎯
⎯
BAT_NL_CF
EN_CHRG
I
I
No-Load Battery Current (Burst Mode
Operation)
No-Load for Regulator, V
23
15
μA
μA
⎯
⎯
⎯
⎯
⎯
⎯
⎯
BAT_NL_BM
BAT_SLP
EN_CHRG
MODE = V , L = 10μH, C = 4.7μF
BAT
●
Battery Current in SLEEP Mode
V
OUT
= 5V, MODE = V
,
BAT
10
20
⎯
⎯
⎯
⎯
⎯
⎯
⎯
EN_CHRG
V
> Regulation Voltage
●
●
V
Buck Undervoltage Lockout
V
BAT
V
BAT
Rising
Falling
2.6
2.4
2.7
2.5
2.8
2.6
V
V
UVLO_BUCK
4080fb
3
LTC4080
ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at TA = 25°C, VCC = 5V, VBAT = 3.8V, VEN_CHRG = 0V, VEN_BUCK = VBAT, VMODE = 0V. (Note 2)
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
0.95
0.85
520
700
15
MAX
UNITS
Ω
R
R
PMOS Switch On-Resistance
NMOS Switch On-Resistance
PMOS Switch Current Limit
NMOS Switch Current Limit
NMOS Zero Current in Normal Mode
ON_P
Ω
ON_N
I
I
I
I
I
t
375
700
mA
mA
mA
mA
mA
μs
LIM_P
LIM_N
ZERO_CF
PEAK
Peak Current in Burst Mode Operation MODE = V
50
20
100
35
150
50
BAT
Zero Current in Burst Mode Operation
Buck Soft-Start Time
MODE = V
ZERO_BM
SS_BUCK
BAT
From the Rising Edge of EN_BUCK to 90%
of Buck Regulated Output
400
Logic
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
EN_CHRG, EN_BUCK, MODE Pin Low to High
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
●
●
●
●
●
V
V
V
Input High Voltage
Input Low Voltage
1.2
V
V
IH
IL
EN_CHRG, EN_BUCK, MODE Pin High to Low
= 5mA
0.4
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
Output Low Voltage (CHRG, ACPR)
I
60
105
1
mV
μA
μA
MΩ
μA
μA
OL
SINK
I
IH
I
IL
Input Current High
EN_BUCK, MODE Pins at 5.5V, V = 5V
–1
–1
1
BAT
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
EN_CHRG, EN_BUCK, MODE Pins at GND
Input Current Low
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
1
R
EN_CHRG Pin Input Resistance
⎯ ⎯ ⎯ ⎯
V
= 5V
⎯ ⎯ ⎯ ⎯ ⎯ ⎯
1.7
3.3
1
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
EN_CHRG
EN_CHRG
●
●
I
CHRG Pin Leakage Current
⎯ ⎯ ⎯ ⎯
V
V
= 4.5V, V
= 5V
⎯
CHRG
⎯
⎯
⎯
⎯
⎯
⎯
⎯
CHRG
BAT
I
ACPR Pin Leakage Current
= 3V, V = 5V
⎯ ⎯ ⎯ ⎯
CHRG
1
⎯
⎯
⎯
⎯
ACPR
CC
Note 4: Although the LTC4080 charger functions properly at 3.75V, full
charge current requires an input voltage greater than the desired final
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.
battery voltage per ΔV
specification.
UVCL1
Note 5: The 2.8V maximum buck undervoltage lockout (V
) exit
UVLO_BUCK
threshold must first be exceeded before the minimum V specification
applies.
Note 2: The LTC4080 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
BAT
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 6: I
with indicated PROG resistor.
is expressed as a fraction of measured full charge current
C/10
Note 3: Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
43°C/W.
4080fb
4
LTC4080
TYPICAL PERFORMANCE CHARACTERISTICS
(TA = 25°C, VCC = 5V, VBAT = 3.8V, unless otherwise specified)
Battery Regulation (Float) Voltage
vs Charge Current
Battery Regulation (Float) Voltage
vs Temperature
Charge Current
vs Battery Voltage
250
200
150
100
50
4.210
4.205
4.200
4.195
4.190
4.185
4.180
4.175
4.170
4.165
4.160
4.21
4.20
4.19
4.18
4.17
4.16
4.15
4.14
4.13
R
= 2k
R
= 2k
PROG
PROG
V
RISING
BAT
TRICKLE CHARGE
0
0
1
2
3
4
5
–30 –10
30
50
70
90
200
CHARGE CURRENT (mA)
250
–50
10
0
50
100
150
BATTERY VOLTAGE (V)
TEMPERATURE (°C)
4080 G01
4080 G02a
4080 G02
Charge Current vs Temperature
with Thermal Regulation
(Constant-Current Mode)
Battery Regulation (Float) Voltage
vs Supply Voltage
PROG Pin Voltage
vs Charge Current
4.25
250
200
150
100
50
1.0
0.8
0.6
0.4
0.2
0
V
V
= 6V
CC
R
= 2k
PROG
= 3V
BAT
4.20
4.15
R
= 2k
PROG
4.10
4.05
4.00
3.95
3.90
THERMAL CONTROL
LOOP IN OPERATION
3.85
0
4.5
5
6
4
5.5
–25
0
25
50
75
–50
100 125
0
75 100
25 50 125 150
175 200
CHARGE CURRENT (mA)
INPUT VOLTAGE (V)
TEMPERATURE (°C)
4080 G03
4080 G04
4080 G05
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
EN_CHRG, EN_BUCK and
Charger FET On-Resistance
vs Temperature
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
EN_CHRG Pin Pulldown
Resistance vs Temperature
MODE Pin Threshold Voltage
vs Temperature
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
V
I
= 4V
CC
BAT
= 350mA
RISING
FALLING
0.50
–30 –10
30
50
70
90
–50
10
–50 –30 –10 10
TEMPERATURE (°C)
90
–50 –30 –10 10
TEMPERATURE (°C)
90
30
50
70
30
50
70
TEMPERATURE (°C)
4080 G06
4080 G07
4080 G08
4080fb
5
LTC4080
TYPICAL PERFORMANCE CHARACTERISTICS
(TA = 25°C, VCC = 5V, VBAT = 3.8V, unless otherwise specified)
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
CHRG and ACPR Pin Output
Low Voltage vs Temperature
Normalized Charger Timer
Period vs Temperature
Buck Oscillator Frequency
vs Battery Voltage
80
1.05
1.00
0.95
0.90
0.85
0.80
2.28
2.27
2.26
2.25
2.24
I
, I
= 5mA
CHRG ACPR
70
60
50
40
30
20
10
2.23
2.22
0
–50 –30 –10 10
90
–50 –30 –10 10
TEMPERATURE (°C)
90
30
50
70
30
50
70
3.0
3.5
4.5
2.5
4.0
TEMPERATURE (°C)
BATTERY VOLTAGE (V)
4080 G09
4080 G10
4080 G11
Buck Oscillator Frequency
vs Temperature
Buck Efficiency vs Load Current
(VOUT = 1.8V)
Buck Efficiency vs Load Current
(VOUT = 1.5V)
100
80
60
40
20
0
1000
100
10
100
80
60
40
20
0
1000
2.4
2.3
2.2
2.1
2.0
1.9
1.8
V
= 3.8V
BAT
EFFICIENCY
(Burst)
V
= 4.5V
EFFICIENCY
(Burst)
BAT
100
10
EFFICIENCY
(PWM)
EFFICIENCY
(PWM)
POWER
POWER
LOSS
LOSS
V
= 2.7V
BAT
(PWM)
(PWM)
0
0
POWER LOSS
(Burst)
POWER LOSS
(Burst)
V
V
= 3.8V
= 1.5V
V
= 3.8V
= 1.8V
BAT
OUT
BAT
OUT
L = 10μH
0.1
0.01
0.1
0.01
V
L = 10μH
C = 4.7μF
C = 4.7μF
40 60
–60 –40 –20
0
20
80 100
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
TEMPERATURE (°C)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
4080 G13a
4080 G12
4080 G13
No-Load Buck Input Current
(Burst Mode Operation)
vs Battery Voltage
Buck Output Voltage
vs Battery Voltage
Buck Output Voltage
vs Temperature
35
30
25
1.810
1.805
1.810
1.805
1.800
1.795
I
= 1mA
OUT
I
= 1mA
OUT
I
= 1mA
= 1.8V
Burst Mode
OPERATION
OUT
OUT
OUT
Burst Mode
V
SET FOR 1.8V
V
SET FOR 1.8V
V
OUT
OPERATION
L = 10μH
PWM MODE
PWM MODE
1.800
1.795
20
15
10
5
1.790
1.785
1.780
1.790
1.785
1.780
0
3.5
BATTERY VOLTAGE (V)
2.5
3.0
4.0
4.5
2.5
3.0
3.5
4.0
4.5
30
–50 –30 –10 10
TEMPERATURE (˚C)
70
90
50
BATTERY VOLTAGE (V)
4080 G14
4080 G17
4080 G15
4080fb
6
LTC4080
TYPICAL PERFORMANCE CHARACTERISTICS
(TA = 25°C, VCC = 5V, VBAT = 3.8V, unless otherwise specified)
No-Load Buck Input Current
(Burst Mode Operation)
vs Temperature
Buck Main Switch (PMOS)
On-Resistance vs Battery Voltage
Buck Main Switch (PMOS)
On-Resistance vs Temperature
1.2
1.0
0.8
0.6
0.4
0.2
0
35
30
1.2
1.0
0.8
0.6
0.4
0.2
0
L = 10μH
C = 4.7μF
OUT
V
= 4.2V
= 3.8V
BAT
V
= 1.8V
V
BAT
25
20
15
10
5
V
= 2.7V
BAT
0
30
TEMPERATURE (˚C)
70
90
–50 –30 –10 10
50
3.5
BATTERY VOLTAGE (V)
2.5
3.0
4.0
4.5
5.0
30
TEMPERATURE (°C)
70
90
–50 –30 –10 10
50
4080 G18
4080 G19
4080 G20
Buck Synchronous Switch (NMOS)
On-Resistance vs Battery Voltage
Buck Synchronous Switch (NMOS)
On-Resistance vs Temperature
1.2
1.0
0.8
0.6
0.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0.2
0
3.5
BATTERY VOLTAGE (V)
2.5
3.0
4.0
4.5
5.0
30
70
90
–50 –30 –10 10
50
TEMPERATURE (°C)
4080 G21
4080 G22
Maximum Output Current
(PWM Mode)
Maximum Output Current
(Burst Mode Operation)
500
400
300
200
100
80
70
60
50
40
30
20
10
0
L = 10μH
L = 10μH
V
SET FOR 1.8V
OUT
V
SET FOR 1.8V
OUT
2.7
3
3.3
3.6
3.9
4.2
4.5
2.7
3
3.3
3.6
3.9
4.2
4.5
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
4080X G24
4080X G23
4080fb
7
LTC4080
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, VCC = 5V, VBAT = 3.8V, unless otherwise
specified)
Output Voltage Waveform
when Switching Between Burst
and PWM Mode (ILOAD = 10mA)
Output Voltage Transient
Step Response (PWM Mode)
Output Voltage Transient
Step Response (Burst Mode)
V
OUT
V
V
OUT
OUT
50mV/DIV
20mV/DIV
20mV/DIV
AC COUPLED
AC COUPLED
AC COUPLED
V
I
I
MODE
LOAD
LOAD
5V/DIV
250mA/DIV
50mA/DIV
I = 0
0V
I = 0
4080 G27
4080 G25
4080 G26
50μs/DIV
50μs/DIV
50μs/DIV
Buck VOUT Soft-Start
(ILOAD = 50mA)
Charger VPROG Soft-Start
V
OUT
1V/DIV
0V
V
PROG
200mV/DIV
V
_
EN BUCK
V = 0
5V/DIV
0V
4080 G28
4080 G29
50μs/DIV
200μs/DIV
4080fb
8
LTC4080
U
U
U
PI FU CTIO S
BAT (Pin 1): Charge Current Output and Buck Regulator pin will be pulled to ground; otherwise the pin is high
Input. Provides charge current to the battery and regulates impedance.
the final float voltage to 4.2V. An internal precision resistor
⎯
⎯
⎯
⎯
CHRG (Pin 6): Open-Drain Charge Status Output. The
charge status indicator pin has three states: pulldown,
high impedance state, and pulse at 2Hz. This output can
be used as a logic interface or as an LED driver. When the
dividerfromthispinsetsthefloatvoltageandisdisconnected
in charger shutdown mode. This pin should be decoupled
with a low ESR capacitor for low-noise buck operation.
⎯
⎯
⎯
⎯
V (Pin2):PositiveInputSupplyVoltage.Thispinprovides battery is being charged, the CHRG pin is pulled low by an
CC
power to the battery charger. V can range from 3.75V internalN-channelMOSFET.Whenthechargecurrentdrops
CC
⎯
⎯
⎯
⎯
to 5.5V. This pin should be bypassed with at least a 1μF to 10% of the full-scale current, the CHRG pin is forced to
capacitor. When V is less than 32mV above the BAT pin a high impedance state. When the battery voltage remains
CC
voltage, the battery charger enters shutdown mode.
⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
below 2.9V for one quarter of the full charge time, the
battery is considered defective, and the CHRG pin pulses
at a frequency of 2Hz with 75% duty cycle.
⎯
⎯
⎯
⎯
EN_CHRG(Pin3):EnableInputPinfortheBatteryCharger.
Pulling this pin above the manual shutdown threshold
(V ) puts the LTC4080 charger in shutdown mode, thus FB(Pin7):FeedbackPinfortheBuckRegulator. Aresistor
IH
stopping the charge cycle. In battery charger shutdown divider from the regulator’s output to the FB pin programs
mode, theLTC4080haslessthan10μAsupplycurrentand the output voltage. Servo value for this pin is 0.8V.
less than 5μA battery drain current if the regulator is not
MODE (Pin 8): Burst Mode Enable Pin. Tie this pin high
running. Enable is the default state, but the pin should be
to force the LTC4080 regulator into Burst Mode operation
tied to GND if unused.
for all load conditions. Tie this pin low to force constant-
PROG (Pin 4): Charge Current Program and Charge frequency mode operation for all load conditions. Do not
Current Monitor Pin. Connecting a 1% resistor, R , to float this pin.
PROG
ground programs the charge current. When charging in
constant-currentmode,thispinservosto1V.Inallmodes,
the voltage on this pin can be used to measure the charge
current using the following formula:
EN_BUCK (Pin 9): Enable Input Pin for the Switching
Regulator. Pull this pin high to enable the regulator, pull
low to shut down. Do not float this pin.
SW (Pin 10): Switch Pin for the Buck Regulator. Minimize
the length of the metal trace connected to this pin. Place
the inductor as close to this pin as possible.
VPROG
IBAT
=
•400
RPROG
⎯ ⎯ ⎯ ⎯
ACPR (Pin 5): Open-Drain Power Supply Status Output. GND (Pin 11): Ground. This pin is the back of the Exposed
When V is greater than the undervoltage lockout PadpackageandmustbesolderedtothePCBforelectrical
CC
⎯
⎯
⎯
⎯
threshold (3.6V) and greater than V + 80mV, the ACPR connection and rated thermal performance.
BAT
4080fb
9
LTC4080
W
BLOCK DIAGRA
2
V
CC
+
3
CHARGER
SHUTDOWN
EN_CHRG
C3
MP3
X1
MP1
115°C
–
+
D3
–
0.82V
TA
X400
R
EN
T
DIE
D1
D2
PROG
0.1V
1
BAT
–
+
–
+
MA
C1
R1
R2
CA
VA
–
+
–
+
MP4
6
1.22V
CHRG
1V
0.1V
CHARGER
ENABLE
PULSE
LOGIC
+
–
2.9V
BAT
C2
CHARGE
CONTROL
BADBAT
4
5
LOGIC
PROG
ACPR
R
PROG
+
–
V
CC
C4
C5
CHARGER
OSCILLATOR
COUNTER
3.6V
+
–
V
+ 80mV
BAT
LINEAR BATTERY CHARGER
MP2
+
–
SYNCHRONOUS BUCK CONVERTER
9
8
L1
PWM
CONTROL
AND DRIVE
V
C
OUT
EN_BUCK
ENABLE BUCK
C6
10
7
SW
MN1
0.82V
C
R7
R8
PL
–
+
–
OUT
2.25MHz
BUCK
OSCILLATOR
ERROR
MODE
FB
C7
AMP
+
0.8V
0.82V
11
4080 BD
GND
Figure 1. LTC4080 Block Diagram
4080fb
10
LTC4080
U
OPERATIO
The LTC4080 is a full-featured linear battery charger with
an integrated synchronous buck converter designed pri-
marily for handheld applications. The battery charger is
capable of charging single-cell 4.2V Li-Ion batteries. The
buck converter is powered from the BAT pin and has a
programmable output voltage providing a maximum load
current of 300mA. The converter and the battery charger
can run simultaneously or independently of each other.
LTC4080 or external components. Another benefit of the
thermal limit is that charge current can be set according
to typical, rather than worst-case, ambient temperatures
for a given application with the assurance that the battery
chargerwillautomaticallyreducethecurrentinworst-case
conditions.
An internal timer sets the total charge time, t
(typi-
TIMER
cally 4.5 hours). When this time elapses, the charge cycle
⎯
⎯
⎯
⎯
terminates and the CHRG pin assumes a high impedance
state even if C/10 has not yet been reached. To restart
the charge cycle, remove the input voltage and reapply
BATTERY CHARGER OPERATION
Featuring an internal P-channel power MOSFET, MP1,
the battery charger uses a constant-current/constant-
voltage charge algorithm with programmable current.
Charge current can be programmed up to 500mA with a
⎯
⎯
⎯
⎯
⎯
⎯
⎯
it or momentarily force the EN_CHRG pin above V . A
IH
new charge cycle will automatically restart if the BAT pin
voltage falls below V
(typically 4.1V).
RECHRG
⎯
⎯
⎯
⎯
final float voltage of 4.2V 0.5%. The CHRG open-drain
status output indicates when C/10 has been reached.
No blocking diode or external sense resistor is required;
thus, the basic charger circuit requires only two external
Constant-Current / Constant-Voltage /
Constant-Temperature
The LTC4080 battery charger uses a unique architecture
to charge a battery in a constant-current, constant-volt-
age and constant-temperature fashion. Figure 1 shows a
Simplified Block Diagram of the LTC4080. Three of the
amplifier feedback loops shown control the constant-cur-
rent,CA,constant-voltage,VA,andconstant-temperature,
TAmodes.Afourthamplifierfeedbackloop,MA,isusedto
increase the output impedance of the current source pair,
MP1 and MP3 (note that MP1 is the internal P-channel
power MOSFET). It ensures that the drain current of MP1
is exactly 400 times the drain current of MP3.
⎯
⎯
⎯
⎯
components. The ACPR open-drain output indicates if the
input voltage, and the difference between V and
V
CC
CC
BAT, are sufficient for charging. An internal termination
timer adheres to battery manufacturer safety guidelines.
Furthermore, the LTC4080 battery charger is capable of
operating from a USB power source.
A charge cycle begins when the voltage at the V pin
CC
rises above 3.6V and approximately 80mV above the BAT
pin voltage, a 1% program resistor is connected from the
⎯
⎯
⎯
⎯
⎯
⎯
⎯
PROGpintoground, andtheEN_CHRGpinispulledbelow
the shutdown threshold (V ). If the battery voltage is less
IL
Amplifiers CA and VA are used in separate feedback loops
to force the charger into constant-current or constant-
voltage mode, respectively. Diodes D1 and D2 provide
priority to either the constant-current or constant-voltage
loop, whichever is trying to reduce the charge current the
most.Theoutputoftheotheramplifiersaturateslowwhich
effectively removes its loop from the system. When in
constant-currentmode,CAservosthevoltageatthePROG
pin to be precisely 1V. VA servos its non-inverting input
to 1.22V when in constant-voltage mode and the internal
resistor divider made up of R1 and R2 ensures that the
battery voltage is maintained at 4.2V. The PROG pin volt-
age gives an indication of the charge current anytime in
the charge cycle, as discussed in “Programming Charge
than 2.9V, the battery charger begins trickle charging at
10% of the programmed charge current.
When the BAT pin approaches the final float voltage of
4.2V, the battery charger enters constant-voltage mode
and the charge current begins to decrease. When the
current drops to 10% of the full-scale charge current, an
internalcomparatorturnsofftheN-channelMOSFETdriving
⎯
⎯
⎯
⎯
the CHRG pin, and the pin becomes high impedance.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
presetvalueofapproximately115°C. Thisfeatureprotects
the LTC4080 from excessive temperature and allows the
user to push the limits of the power handling capability
of a given circuit board without the risk of damaging the
Current” in the Applications Information section.
4080fb
11
LTC4080
U
OPERATIO
⎯
⎯
⎯
⎯
If the die temperature starts to creep up above 115°C
due to internal power dissipation, the transconductance
amplifier, TA, limits the die temperature to approximately
115°C by reducing the charge current. Diode D3 ensures
that TA does not affect the charge current when the die
temperature is below 115°C. In thermal regulation, the
PROG pin voltage continues to give an indication of the
charge current.
the CHRG pin output pulses at a frequency of 2Hz with
a 75% duty cycle. If, for any reason, the battery voltage
rises above 2.9V, the charge cycle will be restarted. To
restart the charge cycle (i.e., when the dead battery is
replaced with a discharged battery less than 2.9V), the
charger must be reset by removing the input voltage and
⎯
⎯
⎯
⎯
⎯
⎯
⎯
reapplyingitortemporarilypullingtheEN_CHRGpinabove
the shutdown threshold.
In typical operation, the charge cycle begins in constant-
currentmodewiththecurrentdeliveredtothebatteryequal
Battery Charger Shutdown Mode
The LTC4080’s battery charger can be disabled by pulling
to 400V/R
. If the power dissipation of the LTC4080
PROG
⎯
⎯
⎯
⎯
⎯
⎯
⎯
the EN_CHRG pin above the shutdown threshold (V ).
results in the junction temperature approaching 115°C,
the amplifier (TA) will begin decreasing the charge current
to limit the die temperature to approximately 115°C. As
the battery voltage rises, the LTC4080 either returns to
constant-current mode or enters constant-voltage mode
straight from constant-temperature mode.
IH
In shutdown mode, the battery drain current is reduced
to less than 2μA and the V supply current to about 5μA
CC
provided the regulator is off. When the input voltage is
not present, the battery charger is in shutdown and the
battery drain current is less than 5μA.
Battery Charger Undervoltage Lockout (UVLO)
⎯ ⎯ ⎯ ⎯
Power Supply Status Indicator (ACPR)
An internal undervoltage lockout circuit monitors the
input voltage and keeps the battery charger off until VCC
rises above 3.6V and approximately 80mV above the BAT
pin voltage. The 3.6V UVLO circuit has a built-in hysteresis
of approximately 0.6V, and the 80mV automatic shutdown
threshold has a built-in hysteresis of approximately 50mV.
During undervoltage lockout conditions, maximum battery
The power supply status output has two states: pulldown
andhighimpedance.ThepulldownstateindicatesthatV
CC
is above the undervoltage lockout threshold and at least
82mV above the BAT voltage (see Undervoltage Lockout).
⎯
⎯
⎯
⎯
When these conditions are not met, the ACPR pin is high
impedanceindicatingthattheLTC4080isunabletocharge
the battery.
drain current is 5μA and maximum supply current is 10μA.
⎯ ⎯ ⎯ ⎯
CHRG Status Output Pin
Undervoltage Charge Current Limiting (UVCL)
Thechargestatusindicatorpinhasthreestates:pulldown,
pulse at 2Hz (see Defective Battery Detection) and high
impedance. The pulldown state indicates that the battery
charger is in a charge cycle. A high impedance state indi-
cates that the charge current has dropped below 10% of
the full-scale current or the battery charger is disabled.
The battery charger in the LTC4080 includes undervoltage
charge current limiting that prevents full charge current
untiltheinputsupplyvoltagereachesapproximately300mV
abovethebatteryvoltage(ΔV
).Thisfeatureisparticu-
UVCL1
larly useful if the LTC4080 is powered from a supply with
long leads (or any relatively high output impedance). See
Applications Information section for further details.
⎯
⎯
⎯
⎯
When the timer runs out (4.5 hrs), the CHRG pin is also
forced to the high impedance state. If the battery charger
is not in constant-voltage mode when the charge current
is forced to drop below 10% of the full-scale current by
Trickle Charge and Defective Battery Detection
⎯
⎯
⎯
⎯
UVCL, CHRG will stay in the strong pulldown state.
At the beginning of a charge cycle, if the battery volt-
age is below 2.9V, the battery charger goes into trickle
charge mode, reducing the charge current to 10% of the
programmed current. If the low battery voltage persists
for one quarter of the total time (1.125 hr), the battery is
assumed to be defective, the charge cycle terminates and
Charge Current Soft-Start
The LTC4080’s battery charger includes a soft-start circuit
tominimizetheinrushcurrentatthestartofachargecycle.
When a charge cycle is initiated, the charge current ramps
4080fb
12
LTC4080
U
OPERATIO
fromzerotofull-scalecurrentoveraperiodofapproximately
180μs. This has the effect of minimizing the transient cur-
rent load on the power supply during start-up.
at the beginning of each clock cycle if the FB pin voltage
is less than the 0.8V reference voltage. The current into
the inductor (and the load) increases until it reaches the
peak current demanded by the error amp. At this point,
the main switch turns off and the synchronous switch
MN1 (N-channel MOSFET) turns on allowing the inductor
current to flow from ground to the load until either the
next clock cycle begins or the current reduces to the zero
Timer and Recharge
The LTC4080’s battery charger has an internal termina-
tion timer that starts when the input voltage is greater
than the undervoltage lockout threshold and at least
80mV above BAT, and the battery charger is leaving
shutdown.
current (I
) level.
ZERO
Oscillator: In constant-frequency mode, the switching
regulator uses a dedicated oscillator which runs at a
fixed frequency of 2.25MHz. This frequency is chosen to
minimize possible interference with the AM band.
At power-up or when exiting shutdown, the charge time
is set to 4.5 hours. Once the charge cycle terminates, the
batterychargercontinuouslymonitorstheBATpinvoltage
using a comparator with a 2ms filter time. When the aver-
age battery voltage falls below 4.1V (which corresponds
to 80%-90% battery capacity), a new charge cycle is initi-
ated and a 2.25 hour timer begins. This ensures that the
battery is kept at, or near, a fully charged condition and
eliminates the need for periodic charge cycle initiations.
Error Amplifier: The error amplifier is an internally com-
pensated transconductance (g ) amplifier with a g
m
m
of 65 μmhos. The internal 0.8V reference voltage is
compared to the voltage at the FB pin to generate a
current signal at the output of the error amplifier. This
current signal is then converted into a voltage signal
⎯
⎯
⎯
⎯
The CHRG output assumes a strong pulldown state dur-
ing recharge cycles until C/10 is reached or the recharge
cycle terminates.
(I ), and represents the peak inductor current required
TH
to achieve regulation.
PWM Comparator: Lossless current sensing converts the
PMOS switch current signal to a voltage which is summed
with the internal slope compensation signal. The PWM
SWITCHING REGULATOR OPERATION:
The switching regulator in the LTC4080 can be turned on
by pulling the EN_BUCK pin above V . It has two user-
comparator compares this summed signal to I and
TH
determines when to turn off the main switch. The switch
current sensing is blanked for ~12ns at the beginning of
each clock cycle to prevent false switch turn-off.
IH
selectablemodesofoperation:constant-frequency(PWM)
mode and Burst Mode Operation. The constant-frequency
mode operation offers low noise at the expense of effi-
ciencywhereastheBurstModeoperationoffersincreased
efficiency at light loads at the cost of increased noise and
output voltage ripple. A detailed description of different
operating modes and different aspects of operation fol-
low. Operations can best be understood by referring to
the Block Diagram.
Burst Mode Operation
Burst Mode operation can be selected by pulling the
MODE pin above V . In this mode, the internal oscil-
IH
lator is disabled, the error amplifier is converted into a
comparator monitoring the FB voltage, and the inductor
current swings between a fixed I
(~80mA) and I
ZERO
PEAK
(35mA) irrespective of the load current as long as the FB
pin voltage is less than or equal to the reference voltage
Constant-Frequency (PWM) Mode Operation
The switching regulator operates in constant-frequency
(PWM) mode when the MODE pin is pulled below V . In
of 0.8V. Once V is greater than 0.8V, the control logic
FB
shuts off both switches along with most of the circuitry
IL
this mode, it uses a current mode architecture including
an oscillator, an error amplifier, and a PWM comparator
for excellent line and load regulation. The main switch
MP2 (P-channel MOSFET) turns on to charge the inductor
and the regulator is said to enter into SLEEP mode. In
SLEEP mode, the regulator only draws about 20μA from
the BAT pin provided that the battery charger is turned
off. When the output voltage droops about 1% from its
4080fb
13
LTC4080
U
OPERATIO
nominal value, the regulator wakes up and the inductor
However, in Burst Mode operation, I
is set to positive
ZERO
current resumes swinging between I
and I
. The
35mA meaning that the synchronous switch is turned off
as soon as the current through the inductor to the output
decreases to 35mA in the discharge cycle. This preserves
thechargeontheoutputcapacitorandincreasestheoverall
efficiency at light loads.
PEAK
ZERO
output capacitor recharges and causes the regulator to
re-enter the SLEEP state if the output load remains light
enough. Thefrequencyofthisintermittentburstoperation
depends on the load current. That is, as the load current
drops further, the regulator turns on less frequently. Thus
BurstModeoperationincreasestheefficiencyatlightloads
byminimizingtheswitchingandquiescentlosses.However,
the output voltage ripple increases to about 2%.
Soft-Start
The LTC4080 switching regulator provides soft-start in
both modes of operation by slowly charging an internal
capacitor. The voltage on this capacitor, in turn, slowly
ramps the current limits of both switches from a low value
to their respective maximum values over a period of about
400μs. The soft-start capacitor is discharged completely
whenever the regulator is disabled.
To minimize ripple in the output voltage, the current limits
for both switches in Burst Mode operation are reduced
to about 20% of their values in the constant-frequency
mode. Also the zero current of the synchronous switch
is changed to about 35mA thereby preventing reverse
conduction through the inductor. Consequently, the regu-
lator can only deliver approximately 55mA of load current
while in Burst Mode operation. Any attempt to draw more
load current will cause the output voltage to drop out of
regulation.
Short-Circuit Protection
In the event of a short circuit at the output or during
start-up, V
will be near zero volts. Since the downward
OUT
slope of the inductor current is ~V /L, the inductor
OUT
current may not get a chance to discharge enough to
avoid a runaway situation. Because the current sensing
is blanked for ~12ns at the beginning of each clock cycle,
inductor current can build up to a dangerously high level
over a number of cycles even if there is a hard current
limit on the main PMOS switch. This is why the switching
regulator in the LTC4080 also monitors current through
the synchronous NMOS switch and imposes a hard limit
on it. If the inductor current through the NMOS switch at
the end of a discharge cycle is not below this limit, the
regulator skips the next charging cycle thereby preventing
inductor current runaway.
Current Limit
To prevent inductor current runaway, there are absolute
current limits (I ) on both the PMOS main switch and
the NMOS synchronous switch. These limits are internally
set at 520mA and 700mA respectively for PWM mode. If
the peak inductor current demanded by the error amplifier
ever exceeds the PMOS I , the error amplifier will be
ignored and the inductor current will be limited to PMOS
LIM
LIM
I
. In Burst Mode operation, the PMOS current limit is
LIM
reduced to 80mA to minimize output voltage ripple.
Zero Current Comparator
Switching Regulator Undervoltage Lockout
Thezeroorreversecurrentcomparatormonitorstheinduc-
tor current to the output and shuts off the synchronous
rectifier when this current reduces to a predetermined
Whenever V
is less than 2.7V, an undervoltage lock-
BAT
out circuit keeps the regulator off, preventing unreliable
operation. However, if the regulator is already running
and the battery voltage is dropping, the undervoltage
comparator does not shut down the regulator until V
drops below 2.5V.
value (I
). In fixed frequency mode, this is set to nega-
ZERO
tive 15mA meaning that the regulator allows the inductor
current to flow in the reverse direction (from the output to
ground through the synchronous rectifier) to a maximum
value of 15mA. This is done to ensure that the regulator
is able to regulate at very light loads without skipping any
cyclestherebykeepingoutputvoltagerippleandnoiselow
at the cost of efficiency.
BAT
4080fb
14
LTC4080
U
OPERATIO
Dropout Operation
Global Thermal Shutdown
When the BAT pin voltage approaches V , the duty cycle
The LTC4080 includes a global thermal shutdown which
shuts off the entire part (both battery charger and switch-
ing regulator) if the die temperature exceeds 160°C. The
LTC4080 resumes normal operation once the temperature
drops approximately 14°C.
OUT
of the switching regulator approaches 100%. When V
BAT
is approximately equal to V , the regulator is said to be
OUT
in dropout. In dropout, the main switch (MP2) stays on
continuously with the output voltage being equal to the
battery voltage minus the voltage drops across the main
switch and the inductor.
U
W U U
APPLICATIO S I FOR ATIO
BATTERY CHARGER
the additional pole created by PROG pin capacitance,
capacitance on this pin must be kept to a minimum. With
no additional capacitance on the PROG pin, the battery
charger is stable with program resistor values as high
as 25k. However, additional capacitance on this node
reduces the maximum allowed program resistor. The pole
frequency at the PROG pin should be kept above 100kHz.
Therefore, if the PROG pin is loaded with a capacitance,
Programming Charge Current
The battery charge current is programmed using a single
resistor from the PROG pin to ground. The charge current
is400timesthecurrentoutofthePROGpin. Theprogram
resistor and the charge current are calculated using the
following equations:
C
, the following equation should be used to calculate
PROG
1V
IBAT
1V
RPROG
the maximum resistance value for R
:
PROG
RPROG = 400 •
, IBAT = 400 •
1
RPROG
≤
2π •105 •CPROG
The charge current out of the BAT pin can be determined
at any time by monitoring the PROG pin voltage and using
the following equation:
Average,ratherthaninstantaneous,batterycurrentmaybe
of interest to the user. For example, when the switching
regulator operating in low-current mode is connected in
parallel with the battery, the average current being pulled
out of the BAT pin is typically of more interest than the
instantaneous current pulses. In such a case, a simple RC
filter can be used on the PROG pin to measure the average
battery current as shown in Figure 2. A 10k resistor has
been added between the PROG pin and the filter capacitor
to ensure stability.
VPROG
R
IBAT
=
•400
Stability Considerations
The LTC4080 battery charger contains two control loops:
constant-voltage and constant-current. The constant-
voltage loop is stable without any compensation when a
battery is connected with low impedance leads. Excessive
lead length, however, may add enough series inductance
to require a bypass capacitor of at least 1μF from BAT to
LTC4080
PROG
GND
CHARGE
10k
CURRENT
MONITOR
CIRCUITRY
GND. Furthermore, a 4.7μF capacitor with a 0.2Ω to 1Ω
series resistor from BAT to GND is required to keep ripple
voltage low when the battery is disconnected.
R
C
FILTER
PROG
4080 F02
In constant-current mode, the PROG pin voltage is in
the feedback loop, not the battery voltage. Because of
Figure 2. Isolating Capacitive Load
on PROG Pin and Filtering
4080fb
15
LTC4080
U
W U U
APPLICATIO S I FOR ATIO
Undervoltage Charge Current Limiting (UVCL)
is approximately 30mW. That is a ten times improvement
over the non-current limited supply power dissipation.
USB powered systems tend to have highly variable source
impedances (due primarily to cable quality and length). A
transientloadcombinedwithsuchimpedancecaneasilytrip
theUVLOthresholdandturnthebatterychargeroffunless
undervoltage charge current limiting is implemented.
USB and Wall Adapter Power
Although the LTC4080 allows charging from a USB port,
a wall adapter can also be used to charge Li-Ion batter-
ies. Figure 3 shows an example of how to combine wall
adapter and USB power inputs. A P-channel MOSFET,
MP1, is used to prevent back conducting into the USB
port when a wall adapter is present and Schottky diode,
D1, is used to prevent USB power loss through the 1k
pulldown resistor.
ConsiderasituationwheretheLTC4080isoperatingunder
normal conditions and the input supply voltage begins to
sag (e.g. an external load drags the input supply down).
If the input voltage reaches V
above the battery voltage, ΔV
(approximately 300mV
), undervoltage charge
UVCL
UVCL
current limiting will begin to reduce the charge current in
an attempt to maintain ΔV between V and BAT. The
Typically a wall adapter can supply significantly more
current than the current-limited USB port. Therefore, an
N-channel MOSFET, MN1, and an extra program resistor
can be used to increase the charge current when the wall
adapter is present.
UVCL
CC
LTC4080 will continue to operate at the reduced charge
current until the input supply voltage is increased or volt-
age mode reduces the charge current further.
Operation from Current Limited Wall Adapter
I
5V WALL
ADAPTER
(300mA)
CHG
1
SYSTEM
LOAD
BAT
LTC4080
D1
2
By using a current limited wall adapter as the input sup-
ply, the LTC4080 can dissipate significantly less power
when programmed for a current higher than the limit of
the supply.
USB
POWER
(200mA)
V
CC
4
+
Li-Ion
BATTERY
MP1
PROG
1.33k
MN1
2k
Considerasituationwhereanapplicationrequiresa200mA
charge current for a discharged 800mAh Li-Ion battery.
If a typical 5V (non-current limited) input supply is avail-
able then the peak power dissipation inside the part can
exceed 300mW.
1k
4080 F03
Figure 3. Combining Wall Adapter and USB Power
Power Dissipation
Now consider the same scenario, but with a 5V input sup-
ply with a 200mA current limit. To take advantage of the
supply, it is necessary to program the LTC4080 to charge
atacurrentgreaterthan200mA.AssumethattheLTC4080
The conditions that cause the LTC4080 battery charger to
reduce charge current through thermal feedback can be
approximated by considering the total power dissipated
in the IC. For high charge currents, the LTC4080 power
dissipation is approximately:
charger is programmed for 300mA (i.e., R
= 1.33kΩ)
PROG
to ensure that part tolerances maintain a programmed
current higher than 200mA. Since the battery charger will
demand a charge current higher than the current limit of
the input supply, the supply voltage will collapse to the
battery voltage plus 200mA times the on-resistance of the
internal PFET. The on-resistance of the battery charger
power device is approximately 0.75Ω with a 5V supply.
The actual on-resistance will be slightly higher due to the
fact that the input supply will have collapsed to less than
5V. The power dissipated during this phase of charging
P = VCC − VBAT •IBAT + PD_BUCK
(
)
D
Where P is the total power dissipated within the IC, V
istheinputsupplyvoltage, V isthebatteryvoltage, I
D
CC
BAT
BAT
D_BUCK
D_BUCK
is the charge current and P
due to the regulator. P
is the power dissipation
can be calculated as:
⎛
⎝ η
⎞
⎠
1
PD_BUCK = VOUT •IOUT
− 1
⎜
⎟
4080fb
16
LTC4080
U
W U U
APPLICATIO S I FOR ATIO
Where V
is the regulated output of the switching
OUT
V
Bypass Capacitor
OUT
regulator, I
CC
is the regulator load and η is the regulator
Many types of capacitors can be used for input bypassing;
however, caution must be exercised when using multi-layer
ceramic capacitors. Because of the self-resonant and high
Q characteristics of some types of ceramic capacitors, high
voltage transients can be generated under some start-up con-
ditions, such as connecting the battery charger input to a live
power source. Adding a 1
X5Rceramiccapacitorwillminimizestart-upvoltagetransients.
For more information, refer to Application Note 88.
efficiency at that particular load.
It is not necessary to perform worst-case power dissipa-
tion scenarios because the LTC4080 will automatically
reduce the charge current to maintain the die temperature
at approximately 115°C. However, the approximate ambi-
ent temperature at which the thermal feedback begins to
protect the IC is:
Ω series resistor in series with an
T = 115°C – PDθJA
A
T = 115°C – (V – V ) • I
• θJA if the regulator
A
CC
BAT
BAT
SWITCHING REGULATOR
is off.
Example: Consider the extreme case when an LTC4080 is
operatingfroma6Vsupplyproviding250mAtoa3VLi-Ion
battery and the regulator is off. The ambient temperature
above which the LTC4080 will begin to reduce the 250mA
charge current is approximately:
Setting the Buck Converter Output Voltage
The LTC4080 regulator compares the FB pin voltage with
aninternal0.8Vreferencetogenerateanerrorsignalatthe
output of the error amplifier. A voltage divider from V
to ground (as shown in the Block Diagram) programs the
output voltage via FB using the formula:
OUT
T = 115°C – (6V – 3V) • (250mA) • 43°C/W
A
T = 115°C – 0.75W • 43°C/W = 115°C – 32.25°C
R7
R8
⎡
⎣
⎤
A
VOUT = 0.8V • 1+
⎢
⎥
⎦
T = 82.75°C
A
If there is more power dissipation due to the regulator,
the thermal regulation will kick in at a somewhat lower
temperature than this. In the above circumstances, the
LTC4080canbeusedabove82.75°C,butthechargecurrent
will be reduced from 250mA. The approximate current at
a given ambient temperature can be calculated:
Keeping the current low (<5μA) in these resistors maxi-
mizes efficiency, but making them too low may allow stray
capacitancetocausenoiseproblemsandreducethephase
margin of the error amp loop. To improve the frequency
response, a phase-lead capacitor (C ) of approximately
PL
10pF can be used. Great care should be taken to route the
FB line away from noise sources, such as the inductor or
the SW line.
115°C − TA
IBAT
=
V
CC − VBAT • θ
(
)
JA
Inductor Selection
Using the previous example with an ambient temperature
of 85°C, the charge current will be reduced to approxi-
mately:
The value of the inductor primarily determines the cur-
rent ripple in the inductor. The inductor ripple
115°C − 85°C
30°C
current ΔI decreases with higher inductance and
IBAT
=
=
= 232.6mA
L
6V − 3V • 43°C /W 129°C /A
(
)
increases with higher V or V
:
IN
OUT
Note: 1V = 1J/C = 1W/A
⎛
⎞
VOUT
f0 •L
VOUT
ΔIL =
• 1−
⎜
⎝
⎟
⎠
Furthermore, the voltage at the PROG pin will change
proportionally with the charge current as discussed in
the Programming Charge Current section.
V
IN
Accepting larger values of ΔI allows the use of low
L
inductances, but results in higher output voltage ripple,
greater core losses, and lower output current capability. A
4080fb
17
LTC4080
U
W U U
APPLICATIO S I FOR ATIO
reasonable starting point for setting ripple current is ΔI
To prevent large V
load conditions, it is also recommended that a ceramic
voltage steps during transient
L
OUT
=0.3 • I , where I
is the peak switch current limit.
LIM
LIM
The largest ripple current occurs at the maximum input
voltage. To guarantee that the ripple current stays below a
specified maximum, the inductor value should be chosen
according to the following equation:
capacitor be used to bypass V . The typical value for
this capacitor is 4.7μF.
OUT
Multilayer Ceramic Chip Capacitors (MLCC) typically have
exceptional ESR performance. MLCCs combined with a
carefullylaidoutboardwithanunbrokengroundplanewill
yield very good performance and low EMI emissions.
⎛
⎞
⎟
VOUT
VOUT
L ≥
• 1−
⎜
⎜
⎝
⎟
⎠
f0 • ΔIL
V
IN
MAX
(
)
There are several types of ceramic capacitors with con-
siderably different characteristics. Y5V and X5R ceramic
capacitors have apparently higher packing density but
poor performance over their rated voltage or temperature
ranges. Under given voltage and temperature conditions,
Y5V, X5R and X7R ceramic capacitors should be com-
pared directly by case size rather than specified value for
a desired minimum capacitance. Some manufacturers
provide excellent data on their websites about achiev-
able capacitance. Table 2 shows a list of several ceramic
capacitor manufacturers.
For applications with V
suggests that an inductor of at least 6.8μH should be used
for proper operation.
= 1.8V, the above equation
OUT
Many different sizes and shapes of inductors are
available from numerous manufacturers. To maximize
efficiency, choose an inductor with a low DC resistance.
Keep in mind that most inductors that are very thin or
have a very small volume typically have much higher
core and DCR losses and will not give the best efficiency.
Also choose an inductor with a DC current rating at least
1.5 times larger than the peak inductor current limit to
ensure that the inductor does not saturate during nor-
mal operation. To minimize radiated noise, use a toroid,
or shielded pot core inductors in ferrite or permalloy
materials. Table 1 shows a list of several inductor manu-
facturers.
Table 2. Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden
AVX
www.t-yuden.com
www.avxcorp.com
www.murata.com
www.tdk.com
Murata
TDK
Table 1. Recommended Surface Mount Inductor Manufacturers
Board Layout Considerations
Coilcraft
Sumida
Murata
Toko
www.coilcraft.com
www.sumida.com
www.murata.com
www.tokoam.com
To be able to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4080’s package has a good thermal
contact to the PC board ground. Correctly soldered to a
2
Input and Output Capacitor Selection
2500mm double-sided 1 oz. copper board, the LTC4080
has a thermal resistance of approximately 43°C/W. Failure
to make thermal contact between the exposed pad on the
backside of the package and the copper board will result
in thermal resistances far greater than 43°C/W.
Since the input current waveform to a buck converter is a
squarewave,itcontainsveryhighfrequencycomponents.
It is strongly recommended that a low equivalent series
resistance (ESR) multilayer ceramic capacitor be used to
bypass the BAT pin which is the input for the converter.
Tantalum and aluminum capacitors are not recommended
because of their high ESR. The value of the capacitor on
BATdirectlycontrolstheamountofinputvoltageripplefor
a given load current. Increasing the size of this capacitor
will reduce the input ripple.
Furthermore due to its high frequency switching circuitry,
it is imperative that the input capacitor, BAT pin capaci-
tor, inductor, and the output capacitor be as close to the
LTC4080 as possible and that there is an unbroken ground
plane under the LTC4080 and all of its high frequency
components.
4080fb
18
LTC4080
U
PACKAGE DESCRIPTIO
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115
TYP
6
0.38 0.10
10
0.675 0.05
3.50 0.05
2.15 0.05 (2 SIDES)
1.65 0.05
1.65 0.10
(2 SIDES)
3.00 0.10
(4 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PACKAGE
OUTLINE
(DD) DFN 1103
5
1
0.25 0.05
0.50 BSC
0.75 0.05
0.200 REF
0.25 0.05
0.50
BSC
2.38 0.10
(2 SIDES)
2.38 0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
MSE Package
10-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1664 Rev B)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 0.102
2.794 0.102
(.110 .004)
0.889 0.127
(.035 .005)
(.081 .004)
1
1.83 0.102
(.072 .004)
5.23
(.206)
MIN
2.083 0.102 3.20 – 3.45
(.082 .004) (.126 – .136)
10
0.50
(.0197)
BSC
0.305 0.038
(.0120 .0015)
TYP
3.00 0.102
(.118 .004)
(NOTE 3)
0.497 0.076
(.0196 .003)
REF
10 9
8
7 6
RECOMMENDED SOLDER PAD LAYOUT
3.00 0.102
(.118 .004)
(NOTE 4)
4.90 0.152
(.193 .006)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
1
2
3
4 5
GAUGE PLANE
0.53 0.152
(.021 .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 0.0508
(.004 .002)
0.50
(.0197)
BSC
MSOP (MSE) 0307 REV B
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
4080fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LTC4080
U
TYPICAL APPLICATIO
Li-Ion Battery Charger with 1.5V Buck Regulator
Buck Efficiency vs Load Current
(VOUT = 1.5V)
R3
100
80
60
40
20
0
1000
100
10
510Ω
EFFICIENCY
(Burst)
D1
500mA
V
CC
V
BAT
CHRG
SW
EFFICIENCY
CC
4.2V
POWER
(PWM)
(3.75V
to 5.5V)
+
R4, 510Ω
C
BAT
Li-Ion
LOSS
(PWM)
ACPR
4.7μF
BATTERY
LTC4080
L1, 1OμH*
D2
EN_CHRG
EN_BUCK
C
10pF
0
PL
POWER LOSS
(Burst)
C
IN
4.7μF
FB
V
R1
715k
OUT
(1.5V/300mA)
V
V
= 3.8V
= 1.5V
BAT
OUT
0.1
0.01
MODE GND PROG
L = 10μH
C = 4.7μF
R
R2
806k
C
OUT
4.7μF
PROG
806Ω
0.01
0.1
1
10
100
1000
4080 TA02
LOAD CURRENT (mA)
4080 G13
*COILCRAFT LPO1704-103M
RELATED PARTS
PART NUMBER
Battery Chargers
LTC3550
DESCRIPTION
COMMENTS
Dual Input USB/AC Adapter Li-Ion Battery Charger Synchronous Buck Converter, Efficiency: 93%, Adjustable Output: 600mA,
with Adjustable Output 600mA Buck Converter
Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power
Detection and Selection
LTC3550-1
Dual Input USB/AC Adapter Li-Ion Battery Charger Synchronous Buck Converter, Efficiency: 93%, Output: 1.875V at 600mA,
with 600mA Buck Converter
Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power
Detection and Selection
LTC4053
LTC4054
USB Compatible Monolithic Li-Ion Battery Charger Standalone Charger with Programmable Timer, Up to 1.25A Charge Current
Standalone Linear Li-Ion Battery Charger with
Thermal Regulation Prevents Overheating, C/10 Termination,
TM
Integrated Pass Transistor in ThinSOT
LTC4061
Standalone Li-Ion Charger with Thermistor
Interface
4.2V, 0.35% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN
4.4V (Max), 0.4% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN
LTC4061-4.4
LTC4062
Standalone Li-Ion Charger with Thermistor
Interface
Standalone Linear Li-Ion Battery Charger with
Micropower Comparator
Up to 1A Charge Current, Charges from USB Port, Thermal Regulation 3mm x
3mm DFN
LTC4063
Li-Ion Charger with Linear Regulator
Up to 1A Charge Current, 100mA, 125mV LDO, 3mm x 3mm DFN
Power Management
LTC3405/LTC3405A 300mA (I ), 1.5MHz, Synchronous Step-Down 95% Efficiency, V : 2.7V to 6V, V
= 0.8V, IQ = 20μA, I < 1μA, ThinSOT
SD
OUT
IN
OUT
DC/DC Converter
Package
LTC3406/LTC3406A 600mA (I ), 1.5MHz, Synchronous Step-Down 95% Efficiency, V : 2.5V to 5.5V, V
= 0.6V, IQ = 20μA, I < 1μA, ThinSOT
SD
OUT
IN
OUT
OUT
OUT
DC/DC Converter
Package
LTC3411
LTC3440
1.25A (I ), 4MHz, Synchronous Step-Down
95% Efficiency, V : 2.5V to 5.5V, V
= 0.8V, IQ = 60μA, I < 1μA, MS Package
SD
OUT
IN
DC/DC Converter
600mA (I ), 2MHz, Synchronous Buck-Boost 95% Efficiency, V : 2.5V to 5.5V, V
= 2.5V, IQ = 25μA, I < 1μA, MS Package
SD
OUT
IN
DC/DC Converter
TM
LTC4411/LTC4412 Low Loss PowerPath Controller in ThinSOT
LTC4413 Dual Ideal Diode in DFN
Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes
2-Channel Ideal Diode ORing, Low Forward On-Resistance, Low Regulated
Forward Voltage, 2.5V ≤ V ≤ 5.5V
IN
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
4080fb
LT 0807 REV B • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
© LINEAR TECHNOLOGY CORPORATION 2006
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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