LTC1731 [Linear]
150mA Standalone Linear Li-Ion Battery Charger in ThinSOT; 150毫安独立线性锂离子电池充电器采用ThinSOT
| 型号： | LTC1731 |
| 厂家： | 
Linear |
| 描述： | 150mA Standalone Linear Li-Ion Battery Charger in ThinSOT |
| 文件： | 总16页 (文件大小：193K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4054L-4.2
150mA Standalone Linear
Li-Ion Battery Charger in ThinSOT
U
FEATURES
DESCRIPTIO
■
Programmable Charge Current Range:
TheLTC®4054Lisacomplete, constant-current/constant-
voltage linear charger for single cell lithium-ion batteries.
Its small size and ability to regulate low charge currents
make the LTC4054L especially well-suited for portable
applications using low capacity rechargeable lithium-ion
coin cells. Furthermore, the LTC4054L is specifically de-
signed to work within USB power specifications.
10mA to 150mA
■
No External MOSFET, Sense Resistor or Blocking
Diode Required
Complete Linear Charger in ThinSOTTM Package for
Single Cell/Coin Cell Lithium-Ion Batteries
Constant-Current/Constant-Voltage Operation with
Thermal Regulation* to Maximize Charge Rate
Without Risk of Overheating
■
■
No external sense resistor is needed, and no blocking di-
ode is required due to the internal MOSFET architecture.
Thermalfeedbackregulatesthechargecurrenttoeliminate
thermaloverdesign.Thechargevoltageisfixedat4.2V,and
the charge current can be programmed externally with a
single resistor. The LTC4054L automatically terminates a
charge cycle when the charge current drops to 1/10th the
programmed value after the final float voltage is reached.
■
Charges Single Cell Li-Ion Batteries Directly
from USB Port
■
■
■
■
■
■
■
■
■
Preset 4.2V Charge Voltage with ±1% Accuracy
Charge Current Monitor Output for Gas Gauging*
Automatic Recharge
Charge Status Output Pin
C/10 Charge Termination
25µA Max Supply Current in Shutdown Mode
2.9V Trickle Charge Threshold
Soft-Start Limits Inrush Current
Available in a 6-Lead Low Profile (1mm)
When the input supply (wall adapter or USB supply) is
removed, the LTC4054L automatically enters a low cur-
rent state, dropping the battery drain current to less than
2µA. The LTC4054L can be put into shutdown mode, re-
ducing the supply current to 25µA.
SOT-23 PackageU
Otherfeaturesincludechargecurrentmonitor,undervoltage
lockout, automatic recharge and a status pin to indicate
charge termination and the presence of an input voltage.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
*U.S. Patent No. 6,522,118
APPLICATIO S
■
Charger for Li-Ion Coin Cell Batteries
■
Portable MP3 Players, Wireless Headsets
■
Bluetooth Applications
Multifunction Wristwatches
■
U
TYPICAL APPLICATIO
Complete Charge Cycle (130mAh Battery)
100
90
80
70
60
50
40
30
20
10
0
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
3.6
3.5
3.4
90mA Li-Ion Single Coin Cell Charger
CONSTANT
CURRENT
CONSTANT
VOLTAGE
V
IN
4.5V TO 6.5V
1µF
4
V
3
5
CC
BAT
90mA
LTC4054L-4.2
4.2V
V
= 5V
CC
JA
PROG
COIN CELL
Li-Ion
BATTERY
θ
= 130°C/W
GND
R
T
= 1.69k
PROG
= 25°C
1.69k
A
2
4054l42 TA01
0
0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25
TIME (HOURS)
4054l42 TA01b
4054l42f
1
LTC4054L-4.2
W W U W
U W
U
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
Input Supply Voltage (VCC) ....................... –0.3V to 10V
PROG............................................. –0.3V to VCC + 0.3V
CHRG........................................................ –0.3V to 10V
BAT............................................................. –0.3V to 7V
BAT Short-Circuit Duration .......................... Continuous
BAT Pin Current ................................................. 200mA
PROG Pin Current................................................ 1.5mA
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range (Note 2) .. –40°C to 85°C
Storage Temperature Range ................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
TOP VIEW
LTC4054LES5-4.2
CHRG 1
GND 2
BAT 3
5 PROG
4 V
CC
S5 PART MARKING
LTAFA
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
TJMAX = 125°C, θJA = 80°C/ W TO 150°C/W
DEPENDING ON PC BOARD LAYOUT (NOTE 3)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.
SYMBOL
PARAMETER
Supply Voltage
Supply Current
CONDITIONS
MIN
TYP
MAX
UNITS
V
●
4.25
6.5
V
CC
I
Charge Mode (Note 4), R
Standby Mode (Charge Terminated)
= 1k
PROG
●
●
●
1200
200
25
2000
500
50
µA
µA
µA
CC
Shutdown Mode (R
Not Connected,
< V , or V < V )
BAT CC UV
PROG
V
CC
V
Regulated Output (Float) Voltage
BAT Pin Current
0°C ≤ T ≤ 85°C, I = 40mA
BAT
4.158
4.2
4.242
V
FLOAT
A
I
R
R
= 15k, Current Mode
= 1k, Current Mode
●
●
●
9.3
142.5
0
10
150
–2.5
±1
10.7
157.5
–6
mA
mA
µA
BAT
PROG
PROG
Standby Mode, V
= 4.2V
BAT
Shutdown Mode (R
Not Connected)
±2
µA
PROG
Sleep Mode, V = 0V
±1
±2
µA
CC
I
Trickle Charge Current
V
< V
, R
= 1k (I = 150mA)
BAT
●
5
15
2.9
80
25
3
mA
V
TRIKL
BAT
TRIKL PROG
V
V
V
V
V
Trickle Charge Threshold Voltage
Trickle Charge Hysteresis Voltage
R
R
= 15k, V
= 15k
Rising
BAT
2.8
60
TRIKL
TRHYS
UV
PROG
PROG
110
3.92
300
mV
V
V
V
Undervoltage Lockout Threshold Voltage From V Low to High
●
●
3.7
150
3.8
200
CC
CC
CC
Undervoltage Lockout Hysteresis Voltage
mV
UVHYS
MSD
Manual Shutdown Threshold Voltage
PROG Pin Rising
PROG Pin Falling
●
●
1.15
0.9
1.21
1.0
1.30
1.1
V
V
V
V
– V Lockout Threshold Voltage
V
V
from Low to High
from High to Low
70
5
100
30
140
50
mV
mV
ASD
CC
BAT
CC
CC
I
C/10 Termination Current Threshold
R
R
= 15k (I = 10mA) (Note 5)
BAT
●
●
0.085
0.088
0.10
0.10
0.115
0.112
mA/mA
mA/mA
TERM
PROG
PROG
= 1k (I
= 150mA) (Note 5)
BAT
V
PROG Pin Voltage
R
= 1k, Current Mode
●
0.93
8
1
1.07
35
V
µA
V
PROG
PROG
CHRG
CHRG
I
CHRG Pin Weak Pull-Down Current
CHRG Pin Output Low Voltage
Recharge Battery Hysteresis Voltage
V
= 5V
20
CHRG
V
I
= 5mA
0.35
150
0.6
200
CHRG
∆V
V
– V
RECHRG
100
mV
RECHRG
FLOAT
4054l42f
2
LTC4054L-4.2
ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
T
LIM
Junction Temperature in Constant
Temperature Mode
120
°C
R
ON
Power FET “ON” Resistance
1.5
Ω
(Between V and BAT)
CC
t
t
t
I
Soft-Start Time
I
= 0 to I
=150V/R
PROG
100
2
µs
ms
µs
SS
BAT
BAT
Recharge Comparator Filter Time
Termination Comparator Filter Time
PROG Pin Pull-Up Current
V
High to Low
0.75
400
1.5
4.5
2500
5
RECHARGE
TERM
BAT
BAT
I
Drops Below I /10
1000
3
CHG
µA
PROG
Note 3: See Thermal Considerations.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 4: Supply current includes PROG pin current (≈1mA) but does not
include any current delivered to the battery through the BAT pin.
Note 5: ITERM is expressed as a fraction of measured full charge current
with indicated PROG resistor.
Note 2: The LTC4054LE-4.2 is guaranteed to meet performance specifica-
tions 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.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
PROG Pin Voltage vs Supply
Voltage (Constant Current Mode)
PROG Pin Voltage vs Temperature
(Constant Current Mode)
Charge Current
vs PROG Pin Voltage
180
150
1.0100
1.0075
1.0050
1.0025
1.0100
1.0075
1.0050
1.0025
V
= 5V
PROG
= 25°C
V
V
T
= 5V
= 4V
V
V
= 5V
= 4V
CC
CC
BAT
CC
BAT
R
T
= 1k
= 25°C
R
= 1k
PROG
A
A
120
90
R
= 1k
PROG
1.0000
0.9975
1.0000
0.9975
R
PROG
= 15k
60
30
0
0.9950
0.9925
0.9900
0.9950
0.9925
0.9900
0
0.25
0.5
V
0.75
(V)
1
1.25
4.5
5
6
–25
0
50
4
6.5
7
–50
75
100
5.5
25
V
CC
(V)
TEMPERATURE (°C)
PROG
4054L G03
4054L G01
4054L G02
4054l42f
3
LTC4054L-4.2
TYPICAL PERFOR A CE CHARACTERISTICS
U W
PROG Pin Pull-Up Current vs
Temperature and Supply Voltage
PROG Pin Current vs PROG Pin
Voltage (Pull-Up Current)
PROG Pin Current vs PROG Pin
Voltage (Clamp Current)
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
3.7
3.5
3.3
3.1
V
V
T
= 5V
BAT
= 25°C
V
V
= 4.3V
= 0V
V
V
T
= 5V
CC
BAT
PROG
CC
= 4.3V
= 4.3V
BAT
–50
= 25°C
A
A
–100
–150
–200
–250
–300
–350
V
= 6.5V
CC
V
= 4.2V
CC
2.9
2.7
2.5
–400
2.5
3
4
4.5
5
5.5
2
3.5
V
50
TEMPERATURE (°C)
100 125
2.4
2.6
–50 –25
0
25
75
2.0
2.1
2.2
2.3
2.5
(V)
V
(V)
PROG
PROG
4054L G06
4054L G04
4054L G05
Regulated Output (Float) Voltage
vs Charge Current
Regulated Output (Float) Voltage
vs Temperature
Regulated Output (Float) Voltage
vs Supply Voltage
4.26
4.24
4.22
4.20
4.18
4.16
4.14
4.215
4.210
4.205
4.200
4.195
4.190
4.185
4.215
4.210
4.205
4.200
4.195
4.190
4.185
V
= 5V
PROG
= 25°C
V
= 5V
PROG
R
A
= 1k
CC
CC
PROG
R
= 600Ω
R
= 1k
T = 25°C
T
A
0
60
90
(mA)
120
150
180
–50
0
25
50
75
100
4
5
5.5
(V)
6
6.5
7
30
–25
4.5
I
TEMPERATURE (°C)
V
BAT
CC
4054L G07
4054L G08
4054L G09
CHRG Pin I-V Curve
(Strong Pull-Down State)
CHRG Pin Current vs Temperature
(Strong Pull-Down State)
CHRG Pin I-V Curve
(Weak Pull-Down State)
25
20
15
10
5
20
22
20
V
V
V
= 5V
= 4V
CHRG
V
V
T
= 5V
= 4V
CC
BAT
CC
BAT
= 25°C
18
16
= 1V
A
18
16
14
12
10
14
12
10
8
V
V
A
= 5V
BAT
= 25°C
CC
6
= 4.3V
T
4
8
0
–25
0
50
75 100 125
4
6
7
–50
25
0
1
2
3
5
0
1
2
3
4
5
6
7
V
CHRG
(V)
TEMPERATURE (°C)
V
CHRG
(V)
4054L G11
4054L G12
4054L G10
4054l42f
4
LTC4054L-4.2
U W
TYPICAL PERFOR A CE CHARACTERISTICS
CHRG Pin Current vs Temperature
(Weak Pull-Down State)
Trickle Charge Current
vs Temperature
Trickle Charge Current
vs Supply Voltage
28
25
22
19
16
13
10
15
12
9
15
12
9
V
V
V
= 5V
CC
= 4.3V
= 5V
BAT
R
PROG
= 1k
R
= 1k
PROG
CHRG
V
V
= 5V
BAT
V
= 2.5V
BAT
CC
= 2.5V
T = 25°C
A
6
6
3
0
3
0
R
PROG
= 15k
R
= 15k
PROG
–50
0
25
50
75
100
–50
0
25
50
75
100
4
5
5.5
(V)
6
6.5
7
–25
–25
4.5
TEMPERATURE (°C)
TEMPERATURE (°C)
V
CC
4054L G13
4054L G14
4054L G15
Trickle Charge Threshold
vs Temperature
Charge Current vs Battery Voltage
Charge Current vs Supply Voltage
160
120
80
3.000
200
160
120
80
V
CC
= 5V
= 1k
V
T
JA
= 4V
BAT
A
R
= 25°C
PROG
2.975
2.950
2.925
2.900
2.875
2.850
2.825
2.800
θ
= 125°C/W
R
= 1k
PROG
V
= 5V
PROG
= 25°C
CC
R
= 1k
T
A
θ
= 125°C/W
JA
40
40
0
R
= 15k
PROG
0
2.7
3.0
3.3
3.6
(V)
3.9
4.2
4.5
–25
0
50
–50
75
100
25
4
5
5.5
(V)
6
6.5
7
4.5
V
BAT
V
TEMPERATURE (°C)
CC
4054L G17
4054L G16
4054L G18
Charge Current
vs Ambient Temperature
Recharge Voltage Threshold
vs Temperature
Power FET “ON” Resistance
vs Temperature
1.8
1.6
1.4
1.2
1.0
0.8
180
150
120
90
4.11
4.09
4.07
4.05
4.03
4.01
3.99
V
V
= 4.1V
V
= 5V
PROG
CC
CC
R
= 4V
R
= 1k
= 1k
BAT
PROG
R
= 1k
PROG
ONSET OF
THERMAL
REGULATION
V
V
= 4V
BAT
CC
JA
= 5V
θ
= 125°C/W
60
30
0
R
PROG
= 15k
25
–50 –25
0
25
50
75 100 125
50
100 125
–50
0
25
50
75
100
–50 –25
0
75
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4054L G21
4054L G19
4054L G20
4054l42f
5
LTC4054L-4.2
U
U
U
PI FU CTIO S
CHRG (Pin 1): Open-Drain Charge Status Output. When
the battery is charging, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the charge cycle is
completed, a weak pull-down of approximately 20µA is
connected to the CHRG pin, indicating an “AC present”
condition. When the LTC4054L detects an undervoltage
lockout condition, CHRG is forced high impedance.
PROG (Pin 5): Charge Current Program, Charge Current
Monitor and Shutdown Pin. The charge current is pro-
grammedbyconnectinga1%resistor, RPROG, toground.
When charging in constant-current mode, this pin servos
to 1V. In all modes, the voltage on this pin can be used to
measure the charge current using the following formula:
IBAT = (VPROG/RPROG) • 150
GND (Pin 2): Ground.
The PROG pin is also used to shut down the charger.
Disconnecting the program resistor from ground allows
a 3µA current to pull the PROG pin high. When it reaches
the1.21Vshutdownthresholdvoltage, thechargerenters
shutdown mode, charging stops and the input supply
current drops to 25µA. This pin is also clamped to
approximately 2.4V. Driving this pin to voltages beyond
the clamp voltage will draw currents as high as 1.5mA.
Reconnecting RPROG to ground will return the charger to
normal operation.
BAT (Pin 3): Charge Current Output. Provides charge
current to the battery and regulates the final float voltage
to 4.2V. An internal precision resistor divider from this pin
sets this float voltage and is disconnected in shutdown
mode.
VCC (Pin 4): Positive Input Supply Voltage. Provides
power to the charger. VCC can range from 4.25V to 6.5V
and should be bypassed with at least a 1µF capacitor.
WhenVCC dropstowithin30mVoftheBATpinvoltage,the
LTC4054L enters shutdown mode, dropping IBAT to less
than 2µA.
4054l42f
6
LTC4054L-4.2
W
BLOCK DIAGRA
4
V
CC
120°C
T
A
T
DIE
1×
150×
–
+
BAT
3
5µA
MA
R1
R2
+
VA
–
CA
+
–
–
+
REF
1.21V
SHDN
C1
R3
1V
R4
0.1V
R5
+
–
C2
CHRG
1
STANDBY
V
CC
3µA
C3
+
–
2.9V
TO BAT
PROG
GND
5
2
R
PROG
4054L42 BD
4054l42f
7
LTC4054L-4.2
U
OPERATIO
The LTC4054L is a single cell lithium-ion battery charger
using a constant-current/constant-voltage algorithm. Its
ability to control charge currents as low as 10mA make it
well-suited for charging low capacity lithium-ion coin cell
batteries. The LTC4054L includes an internal P-channel
powerMOSFETandthermalregulationcircuitry.Noblock-
ing diode or external sense resistor is required; thus, the
basic charger circuit requires only three external compo-
nents. Furthermore, the LTC4054L is capable of operating
from a USB power source.
The charge current out of the BAT pin can be determined
at any time by monitoring the PROG pin voltage using the
following equation:
VPROG
RPROG
IBAT
=
•150
Charge Termination
The charge cycle is terminated when the charge current
falls to 1/10th the programmed value after the final float
voltage is reached. This condition is detected by using an
internal, filtered comparator to monitor the PROG pin.
When the PROG pin voltage falls below 100mV1 for longer
than tTERM (typically 1ms), charging is terminated. The
charge current is latched off and the LTC4054L enters
standby mode, where the input supply current drops to
200µA.(Note:C/10terminationisdisabledintricklecharg-
ing and thermal limiting modes.)
Normal Charge Cycle
The charge cycle begins when the voltage at the VCC pin
rises above the UVLO level and a 1% program resistor is
connected from the PROG pin to ground. If the BAT pin is
less than 2.9V, the charger enters trickle charge mode. In
this mode, the LTC4054L supplies approximately 1/10 the
programmed charge current in order to bring the battery
voltage up to a safe level for full current charging.
While charging, transient loads on the BAT pin can cause
thePROGpintofallbelow100mVforshortperiodsoftime
before the DC charge current has dropped to 1/10th the
programmed value. The 1ms filter time (tTERM) on the
termination comparator ensures that transient loads of
this nature do not result in premature charge cycle termi-
nation. Once the average charge current drops below
1/10th the programmed value for longer than tTERM , the
LTC4054L terminates the charge cycle and ceases to
provide any current through the BAT pin. In this state, all
loads on the BAT pin must be supplied by the battery.
When the BAT pin voltage rises above 2.9V, the charger
enters constant-current mode, where the programmed
chargecurrentissuppliedtothebattery.WhentheBATpin
approaches the final float voltage (4.2V), the LTC4054L
enters constant-voltage mode and the charge current
begins to decrease. When the charge current drops to
1/10 of the programmed value, the charge cycle ends.
Programming Charge Current
The charge current is programmed using a single resistor
from the PROG pin to ground. The battery charge current
is150timesthecurrentoutofthePROGpin. Theprogram
resistor and the charge current are calculated using the
following equations:
The LTC4054L constantly monitors the BAT pin voltage in
standby mode. If this voltage drops below the 4.05V
recharge threshold (VRECHRG), another charge cycle be-
gins and current is once again supplied to the battery. To
manuallyrestartachargecyclewheninstandbymode, the
input voltage must be removed and reapplied, or the
charger must be shut down and restarted using the PROG
pin. Figure 1 shows the state diagram of a typical charge
cycle.
150V
ICHG
150V
RPROG
RPROG
=
, ICHG =
1Any external sources that hold the PROG pin above 100mV will prevent the LTC4054L from
terminating a charge cycle.
4054l42f
8
LTC4054L-4.2
U
OPERATIO
POWER ON
BAT < 2.9V
TRICKLE CHARGE
MODE
PROG
RECONNECTED
OR
UVLO CONDITION
STOPS
1/10TH FULL CURRENT
CHRG: STRONG
PULL-DOWN
BAT > 2.9V
BAT > 2.9V
SHUTDOWN MODE
DROPS TO <25µA
CHARGE MODE
I
CC
FULL CURRENT
CHRG: Hi-Z IN UVLO
WEAK PULL-DOWN
OTHERWISE
CHRG: STRONG
PULL-DOWN
PROG < 100mV
STANDBY MODE
NO CHARGE CURRENT
PROG FLOATED
OR
UVLO CONDITION
CHRG: WEAK
PULL-DOWN
2.9V < BAT < 4.05V
4054L42 F01
Figure 1. State Diagram of a Typical Charge Cycle
allows the user to push the limits of the power handling
capabilityofagivencircuitboardwithoutriskofdamaging
the LTC4054L. The charge current can be set according to
typical (not worst-case) ambient temperature with the
assurance that the charger will automatically reduce the
current in worst-case conditions. ThinSOT power consid-
erationsarediscussedfurtherintheApplicationsInforma-
tion section.
Charge Status Indicator (CHRG)
The charge status output has three different states: strong
pull-down (~10mA), weak pull-down (~20uA), and high
impedance. The strong pull-down state indicates that the
LTC4054L is in a charge cycle. Once the charge cycle has
terminated, the pin state is determined by undervoltage
lockout conditions. A weak pull-down indicates that VCC
meets the UVLO conditions and the LTC4054L is ready to
charge. High impedance indicates that LTC4054L is in
undervoltage lock-out mode: either VCC is within 100mV
of the BAT pin voltage or insufficient voltage is applied to
the VCC pin. A microprocessor can be used to distinguish
between these three states—this method is discussed in
the Applications Information section.
Undervoltage Lockout (UVLO)
Aninternalundervoltagelockoutcircuitmonitorstheinput
voltageandkeepsthechargerinshutdownmodeuntilVCC
risesabovetheundervoltagelockoutthreshold. TheUVLO
circuit has a built-in hysteresis of 200mV. Furthermore, to
protect against reverse current in the power MOSFET, the
UVLO circuit keeps the charger in shutdown mode if VCC
falls to within 30mV of the battery voltage. If the UVLO
comparator is tripped, the charger will not come out of
shutdown mode until VCC rises 100mV above the battery
voltage.
Thermal Limiting
Aninternalthermalfeedbackloopreducestheprogrammed
charge current if the die temperature attempts to rise
above a preset value of approximately 120°C. This feature
protects the LTC4054L from excessive temperature and
4054l42f
9
LTC4054L-4.2
U
OPERATIO
Manual Shutdown
Automatic Recharge
At any point in the charge cycle, the LTC4054L can be put
into shutdown mode by removing RPROG thus floating the
PROG pin. This reduces the battery drain current to less
than 2µA and the supply current to less than 50µA. A new
charge cycle can be initiated by reconnecting the program
resistor.
Once the charge cycle is terminated, the LTC4054L con-
tinuously monitors the voltage on the BAT pin using a
comparator with a 2ms filter time (tRECHARGE). A charge
cycle restarts when the battery voltage falls below 4.05V
(whichcorrespondstoapproximately80%to90%battery
capacity). This ensures that the battery is kept at or near
a fully charged condition and eliminates the need for
periodic charge cycle initiations. CHRG output enters a
strong pull-down state during recharge cycles.
In manual shutdown, the CHRG pin is in a weak pull-down
state as long as VCC is high enough to exceed the UVLO
conditions. The CHRG pin is in a high impedance state if
the LTC4054L is in undervoltage lockout mode: either VCC
is within 100mV of the BAT pin voltage or insufficient
voltage is applied to the VCC pin.
4054l42f
10
LTC4054L-4.2
W U U
APPLICATIO S I FOR ATIO
U
Stability Considerations
Average, rather than instantaneous, charge current may
beofinteresttotheuser.Forexample,ifaswitchingpower
supply 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.
The constant-voltage mode feedback loop is stable with-
out an output capacitor provided a battery is connected to
the charger output. With no battery present, an output
capacitor is recommended to reduce ripple voltage. When
using high value, low ESR ceramic capacitors, it is recom-
mended to add a 1Ω resistor in series with the capacitor.
No series resistor is needed if tantalum capacitors are
used.
In constant-current mode, the PROG pin is in the feedback
loop, not the battery. The constant-current mode stability
is affected by the impedance at the PROG pin. With no
additional capacitance on the PROG pin, the charger is
stable with program resistor values as high as 20k. How-
ever, 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, CPROG, the
following equation can be used to calculate the maximum
Power Dissipation
The conditions that cause the LTC4054L to reduce charge
currentthroughthermalfeedbackcanbeapproximatedby
considering the power dissipated in the IC. Nearly all of
this power dissipation is generated from the internal
MOSFET—this is calculated to be approximately:
PD = (VCC – VBAT) • IBAT
where PD is the power dissipated, VCC is the input supply
voltage, VBAT is the battery voltage and IBAT is the charge
current. The approximate ambient temperature at which
the thermal feedback begins to protect the IC is:
resistance value for RPROG
:
1
RPROG
≤
2π •105 •CPROG
TA = 120°C – PDθJA
TA = 120°C – (VCC – VBAT) • IBAT • θJA
CHARGE
10k
CURRENT
MONITOR
CIRCUITRY
PROG
LTC4054L
GND
R
PROG
C
FILTER
4054L42 F02
Figure 2. Isolating Capacitive Load on PROG Pin and Filtering
4054l42f
11
LTC4054L-4.2
W U U
U
APPLICATIO S I FOR ATIO
Example: An LTC4054L operating from a 6V wall adapter
is programmed to supply 150mA full-scale current to a
discharged Li-Ion battery with a voltage of 3.75V. Assum-
ing θJA is 200°C/W, the ambient temperature at which the
LTC4054L will begin to reduce the charge current is
approximately:
Thermal Considerations
BecauseofthesmallsizeoftheThinSOTpackage, itisvery
important to use a good thermal PC board layout to
maximize the available charge current. The thermal path
for the heat generated by the IC is from the die to the
copper lead frame, through the package leads, (especially
the ground lead) to the PC board copper. The PC board
copper is the heat sink. The footprint copper pads should
be as wide as possible and expand out to larger copper
areas to spread and dissipate the heat to the surrounding
ambient. Feedthrough vias to inner or backside copper
layers are also useful in improving the overall thermal
performance of the charger. Other heat sources on the
board, not related to the charger, must also be considered
when designing a PC board layout because they will affect
overalltemperatureriseandthemaximumchargecurrent.
TA = 120°C – (6V – 3.75V) • (150mA) • 200°C/W
TA = 120°C – 0.3375W • 200°C/W = 120°C – 67.5°C
TA = 52.5°C
The LTC4054L can be used above 52.5°C, but the charge
current will be reduced from 150mA. The approximate
current at a given ambient temperature can be approxi-
mated by:
120°C – TA
IBAT
=
V – V
• θ
JA
(
)
CC
BAT
The following table lists thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 3/32" FR-4 board with the device
mounted on topside.
Using the previous example with an ambient tempera-
ture of 60°C, the charge current will be reduced to
approximately:
Table 1. Measured Thermal Resistance (2-Layer Board*)
COPPER AREA
TOPSIDE BACKSIDE
BOARD
AREA
THERMAL RESISTANCE
JUNCTION-TO-AMBIENT
120°C – 60°C
60°C
IBAT
=
=
6V – 3.75V • 200°C/W 450°C/A
(
)
2
2
2
2
2
2
2
2
2
2
2
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
125°C/W
125°C/W
130°C/W
135°C/W
150°C/W
2
IBAT = 133mA
1000mm
2
225mm
100mm
Moreover, when thermal feedback reduces the charge
current, the voltage at the PROG pin is also reduced
proportionally as discussed in the Operation section.
2
2
50mm
*Each layer uses one ounce copper
It is important to remember that LTC4054L applications
do not need to be designed for worst-case thermal condi-
tions since the IC will automatically reduce power dissipa-
tionwhenthejunctiontemperaturereachesapproximately
120°C.
Table 2. Measured Thermal Resistance (4-Layer Board**)
COPPER AREA
(EACH SIDE)
BOARD
AREA
THERMAL RESISTANCE
JUNCTION-TO-AMBIENT
2***
2
2500mm
2500mm
80°C/W
**Top and bottom layers use two ounce copper, inner layers use one
ounce copper.
2
***10,000mm total copper area
4054l42f
12
LTC4054L-4.2
W U U
APPLICATIO S I FOR ATIO
U
VCC Bypass Capacitor
cycle begins and the CHRG pin pulls to ground. The
CHRG pin can sink up to 10mA to drive an LED that
indicates that a charge cycle is in progress.
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 capaci-
tors, high voltage transients can be generated under some
start-up conditions, such as connecting the charger input
to a live power source. Adding a 1.5Ω resistor in series
with an X5R ceramic capacitor will minimize start-up
voltage transients. For more information, refer to Applica-
tion Note 88.
When the battery is nearing full charge, the charger enters
the constant-voltage portion of the charge cycle and the
charge current begins to drop. When the charge current
drops below 1/10 of the programmed current, the charge
cycle ends, and the strong pull-down is replaced by the
20µA pull-down, indicating that the charge cycle has
ended. If the input voltage is removed or drops below the
undervoltage lockout threshold, the CHRG pin becomes
high impedance. Figure 3 shows that by using two differ-
entvaluepull-upresistors,amicroprocessorcandetectall
three states from this pin.
Charge Current Soft-Start
The LTC4054L includes a soft-start circuit to minimize the
inrushcurrentatthestartofachargecycle. Whenacharge
cycleisinitiated,thechargecurrentrampsfromzerotothe
full-scale current over a period of approximately 100µs.
This has the effect of minimizing the transient current load
on the power supply during start-up.
To detect when the LTC4054L is in charge mode, force the
digital output pin (OUT) high and measure the voltage at
the CHRG pin. The N-channel MOSFET will pull the pin
voltage low even with the 2k pull-up resistor. Once the
charge cycle terminates, the N-channel MOSFET is turned
off and a 20µA current source is connected to the CHRG
pin. The IN pin will then be pulled high by the 2k pull-up
resistor. Todetermineifthereisaweakpull-downcurrent,
the OUT pin should be forced to a high impedance state.
The weak current source will pull the IN pin low through
the 800k resistor; if CHRG is high impedance, the IN pin
will be pulled high, indicating that the part is in a UVLO
state.
CHRG Status Output Pin
The CHRG pin can provide an indication that the input
voltage is greater than the undervoltage lockout thresh-
old level. A weak pull-down current of approximately
20µA indicates that sufficient voltage is applied to VCC to
begin charging. When a discharged battery is connected
to the charger, the constant current portion of the charge
+
V
V
DD
V
CC
800k
LTC4054L
CHRG
µPROCESSOR
2k
OUT
IN
4054L42 F03
Figure 3. Using a Microprocessor to Determine CHRG State
4054l42f
13
LTC4054L-4.2
W U U
U
APPLICATIO S I FOR ATIO
Reverse Polarity Input Voltage Protection
USB and Wall Adapter Power
In some applications, protection from reverse polarity
voltage on VCC is desired. If the supply voltage is high
enough, a series blocking diode can be used. In other
cases,wherethevoltagedropmustbekeptlowaP-channel
MOSFET can be used (as shown in Figure 4).
The LTC4054L allows charging from both a wall adapter
and a USB port. Figure 5 shows an example of how to
combine wall adapter and USB power inputs. A P-channel
MOSFET,MP1,isusedtopreventbackconductingintothe
USB port when a wall adapter is present and a Schottky
diode, D1, is used to prevent USB power loss through the
1k pull-down resistor.
DRAIN-BULK
DIODE OF FET
LTC4054L
CC
V
V
100mA
IN
3
5
5V WALL
ADAPTER
SYSTEM
LOAD
BAT
4054L42 F04
LTC4054L-4.2
D1
+
4
USB
POWER
Li-Ion
BATTERY
PROG
V
CC
Figure 4. Low Loss Input Reverse Polarity Protection
MP1
1k
1.5k
4054l42 F05
Figure 5. Combining Wall Adapter and USB Power
4054l42f
14
LTC4054L-4.2
U
PACKAGE DESCRIPTIO
S5 Package
5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
0.62
MAX
0.95
REF
2.90 BSC
(NOTE 4)
1.22 REF
1.50 – 1.75
(NOTE 4)
2.80 BSC
1.4 MIN
3.85 MAX 2.62 REF
PIN ONE
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45 TYP
5 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.90 BSC
0.09 – 0.20
(NOTE 3)
NOTE:
S5 TSOT-23 0302
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
4054l42f
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LTC4054L-4.2
U
TYPICAL APPLICATIO S
Full Featured Single Cell Li-Ion Charger
Basic Li-Ion Battery Charger with
Reverse Polarity Input Protection
V
IN
= 5V
100mA
4
3
5
5V WALL
ADAPTER
V
BAT
CC
1µF
100mA
CHARGING
4
LTC4054L-4.2
V
3
5
+
CC
PROG
GND
BAT
1µF
330Ω
LTC4054L-4.2
2
1
1.5k
+
CHRG
PROG
GND
2
1.5k
4054L42 TA03
SHDN
4054L42 TA02
USB/Wall Adapter Power Li-Ion Charger
100mA
5V WALL
ADAPTER
3
BAT
+
LTC4054L-4.2
Li-Ion
CELL
4
USB
POWER
V
CC
5
1µF
PROG
GND
2
1k
1.5k
4054L42 TA05
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1731
Lithium-Ion Linear Battery Charger Controller
Simple Charger uses External FET, Features Preset Voltages, C/10
Charger Detection and Programmable Timer
LTC1732
Lithium-Ion Linear Battery Charger Controller
Simple Charger uses External FET, Features Preset Voltages, C/10
Charger Detection and Programmable Timer, Input Power Good Indication
LTC1733
LTC1734
LTC1734L
LTC1998
LTC4050
Monolithic Lithium-Ion Linear Battery Charger
Lithium-Ion Linear Battery Charger in ThinSOT
Lithium-Ion Linear Battery Charger in ThinSOT
Lithium-Ion Low Battery Detector
Standalone Charger with Programmable Timer, Up to 1.5A Charge Current
Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed
Low Current Version of LTC1734
1% Accurate 2.5µA Quiescent Current, SOT-23
Lithium-Ion Linear Battery Charger Controller
Simple Charger uses External FET, Features Preset Voltages, C/10
Charger Detection and Programmable Timer, Input Power Good Indication,
Thermistor Interface
LTC4052
LTC4053
LTC4054
Monolithic Lithium-Ion Battery Pulse Charger
No Blocking Diode or External Power FET Required, Safety Current Limit
Standalone Charger with Programmable Timer, Up to 1.25A Charge Current
USB Compatible Monolithic Li-Ion Battery Charger
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in ThinSOT
No External MOSFET, Sense Resistor or Blocking Diode Required,
Charge Current Monitor for Gas Gauging, C/10 Charge Termination
LTC4056
LTC4057
LTC4058
LTC4410
Standalone Lithium-Ion Linear Battery Charger
in ThinSOT
Standalone Charger with Programmable Timer, No Blocking Diode,
No Sense Resistor Needed
Monolithic Lithium-Ion Linear Battery Charger
with Thermal Regulation in ThinSOT
No External MOSFET, Sense Resistor or Blocking Diode Required,
Charge Current Monitor for Gas Gauging
950mA Standalone Li-Ion Charger in 3mm × 3mm
DFN
USB Compatible, Thermal Regulation Protects Against Overheating
USB Power Manager
For Simultaneous Operation of USB Peripheral and Battery Charging from USB
Port, Keeps Current Drawn from USB Port Constant, Keeps Battery Fresh, Use
with the LTC4053, LTC1733, or LTC4054
4054l42f
LT/TP 1203 1K • PRINTED IN USA
16 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2003
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