1
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
Standalone Linear
Li-Ion Battery Charger with
Thermal Regulation in DFN
■
Programmable Charge Current Up to 950mA
■
Complete Linear Charger in DFN Package
■
No MOSFET, Sense Resistor or Blocking Diode
Required
■
Thermal Regulation Maximizes Charge Rate
Without Risk of Overheating*
■
Battery Kelvin Sensing Improves Charging Accuracy
■
Charges Directly from a USB Port
■
C/10 Charge Termination
■
Preset 4.2V Charge Voltage with ±1% Accuracy
■
Charge Current Monitor Output for Gas Gauging*
■
Automatic Recharge
■
Charge Status Output
■
“AC Present” Output
■
2.9V Trickle Charge Threshold (LTC4058)
■
Available Without Trickle Charge (LTC4058X)
■
Soft-Start Limits Inrush Current
■
Low Profile (3mm × 3mm × 0.75mm) DFN Package
■
Cellular Telephones, PDAs, MP3 Players
■
Bluetooth Applications
, LTC and LT are registered trademarks of Linear Technology Corporation.
The LTC
®
4058 is a complete constant-current/constant-
voltage linear charger for single cell lithium-ion batteries.
Its DFN package and low external component count make
the LTC4058 ideally suited for portable applications. Fur-
thermore, the LTC4058 is designed to work within USB
power specifications.
The LTC4058 can Kelvin sense the battery terminal for
more accurate float voltage charging. No external sense
resistor or external blocking diode are required due to the
internal MOSFET architecture. Thermal feedback regu-
lates the charge current to limit the die temperature during
high power operation or high ambient temperature condi-
tions. The charge voltage is fixed at 4.2V and the charge
current is programmed with a resistor. The LTC4058
terminates the charge cycle when the charge current
drops to 10% of the programmed value after the final float
voltage is reached.
When the input supply (wall adapter or USB supply) is
removed, the LTC4058 enters a low current state dropping
the battery drain current to less than 2µA. Other features
include charge current monitor, undervoltage lockout,
automatic recharge and status pins to indicate charge
termination and the presence of an input voltage.
BATV
CC
BSENSE
CHRG
1.65k
405842 TA01
1µF
V
IN
4.5V TO 6.5V
1-CELL
Li-Ion
BATTERY
LTC4058-4.2
600mA
ACPR
EN PROG
GND
+
TIME (HOURS)
0
CHARGE CURRENT (mA)
1.5
405842 TA02
0.5 1.0 2.25
700
600
500
400
300
200
100
0
4.75
4.50
4.25
4.00
3.75
3.50
3.25
3.00
0.25 0.75 1.25 2.01.75
CONSTANT
VOLTAGE
CONSTANT
CURRENT
BATTERY VOLTAGE (V)
V
CC
= 5V
θ
JA
= 40°C/W
R
PROG
= 1.65k
T
A
= 25°C
Complete Charge Cycle (750mAh Battery)
*US Patent 6,522,118
Single Cell Li-Ion Battery Charger with Kelvin Sense
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
(Note 1)
Input Supply Voltage (V
CC
) ....................... –0.3V to 10V
PROG............................................. –0.3V to V
CC
+ 0.3V
BAT, BSENSE.............................................. –0.3V to 7V
CHRG, ACPR, EN ...................................... –0.3V to 10V
BAT Short-Circuit Duration .......................... Continuous
BAT Pin Current ........................................................ 1A
PROG Pin Current................................................... 1mA
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range (Note 2) .. –40°C to 85°C
Storage Temperature Range ................. –65°C to 125°C
T
JMAX
= 125°C, θ
JA
= 40°C/W (NOTE 3)
EXPOSED PAD IS GROUND (PIN 9)
MUST BE SOLDERED TO PCB
ORDER PART
NUMBER
DD PART MARKING
LAEV
LBDH
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC
Input Supply Voltage ●4.25 6.5 V
I
CC
Input Supply Current Charge Mode (Note 4), R
PROG
= 10k ●0.3 1 mA
Standby Mode (Charge Terminated) ●200 500 µA
Shutdown Mode (EN = 5V, V
CC
< V
BSENSE
●25 50 µA
or V
CC
< V
UV
)
V
FLOAT
Regulated Output (Float) Voltage 0°C ≤ T
A
≤ 85°C, 4.3V < V
CC
< 6.5V 4.158 4.2 4.242 V
I
BAT
BAT Pin Current R
PROG
= 10k, Current Mode ●93 100 107 mA
R
PROG
= 2k, Current Mode ●465 500 535 mA
I
BSENSE
BSENSE Pin Current (Note 5) Standby Mode, V
BSENSE
= 4.2V ●–2.5 –6 µA
Shutdown Mode (EN = 5V, V
CC
< V
BSENSE
or ±1±2µA
V
CC
< V
UV
)
Sleep Mode, V
CC
= 0V ±1±2µA
I
TRIKL
Trickle Charge Current V
BSENSE
< V
TRIKL
, R
PROG
= 2k (Note 6) ●30 45 60 mA
V
TRIKL
Trickle Charge Threshold Voltage R
PROG
= 10k, V
BSENSE
Rising (Note 6) 2.8 2.9 3 V
V
TRHYS
Trickle Charge Hysteresis Voltage R
PROG
= 10k (Note 6) 60 80 110 mV
V
UV
V
CC
Undervoltage Lockout Voltage From V
CC
Low to High ●3.7 3.8 3.92 V
V
UVHYS
V
CC
Undervoltage Lockout Hysteresis ●150 200 300 mV
V
EN(IL)
EN Pin Input Low Voltage ●0.4 0.7 V
V
EN(IH)
EN Pin Input High Voltage ●0.7 1 V
R
EN
EN Pin Pull-Down Resistor ●1.2 2 5 MΩ
V
ASD
V
CC
– V
BSENSE
Lockout Threshold V
CC
from Low to High 70 100 140 mV
V
CC
from High to Low 5 30 50 mV
I
TERM
C/10 Termination Current Threshold R
PROG
= 10k (I
CHG
= 100mA) (Note 7) ●0.085 0.10 0.115 mA/mA
R
PROG
= 2k (I
CHG
= 500mA) ●0.085 0.10 0.115 mA/mA
V
PROG
PROG Pin Voltage R
PROG
= 10k, Current Mode 0.93 1 1.07 V
V
CHRG
CHRG Pin Output Low Voltage I
CHRG
= 5mA 0.35 0.6 V
V
ACPR
ACPR Pin Output Low Voltage I
ACPR
= 5mA 0.35 0.6 V
∆V
RECHRG
Recharge Battery Threshold Voltage V
FLOAT
– V
RECHRG
, 0°C ≤ T
A
≤ 85°C 60 100 140 mV
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
ELECTRICAL CHARACTERISTICS
Consult LTC Marketing for parts specified with wider operating temperature ranges.
LTC4058EDD-4.2
LTC4058XEDD-4.2
TOP VIEW
9
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
5
6
7
8
4
3
2
1BSENSE
BAT
CHRG
GND
EN
ACPR
V
CC
PROG
3
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: The LTC4058E-4.2/LTC4058XE-4.2 are guaranteed to meet
performance specifications from 0°C to 70°C. Specifications over the
–40°C to 85°C operating temperature range are assured by design,
characterization and correlation with statistical process controls.
Note 3: Failure to solder the exposed backside of the package to the PC
board will result in a thermal resistance much higher than 40°C/W.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
T
LIM
Junction Temperature in Constant 120 °C
Temperature Mode
R
ON
Power FET “ON” Resistance 600 mΩ
(Between V
CC
and BAT)
t
SS
Soft-Start Time I
BAT
= 0 to I
BAT
=1000V/R
PROG
100 µs
t
RECHARGE
Recharge Comparator Filter Time V
BSENSE
High to Low 0.75 2 4.5 ms
t
TERM
Termination Comparator Filter Time I
BAT
Drops Below I
CHG
/10 400 1000 2500 µs
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
Note 4: Supply current includes PROG pin current (approximately 100µA)
but does not include any current delivered to the battery through the BAT
pin (approximately 100mA).
Note 5: For all Li-Ion applications, the BSENSE pin must be electrically
connected to the BAT pin.
Note 6: This parameter is not applicable to the LTC4058X.
Note 7: I
TERM
is expressed as a fraction of measured full charge current
with indicated PROG resistor.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
PROG Pin Voltage vs Supply
Voltage (Constant Current Mode)
V
CC
(V)
4
0.985
V
PROG
(V)
0.990
0.995
1.000
1.005
1.015
4.5 5 5.5 6
405842 G01
6.5 7
1.010
V
CC
= 5V
V
BAT
= V
BSENSE
= 4V
T
A
= 25°C
R
PROG
= 10k
TEMPERATURE (°C)
–50
V
PROG
(V)
0.9975
1.0000
1.0025
25 75
405842 G02
0.9950
0.9925
0.9900 –25 0 50
1.0050
1.0075
1.0100
100
V
CC
= 5V
V
BAT
= V
BSENSE
= 4V
R
PROG
= 10k
VPROG (V)
0
0
IBAT (mA)
100
200
300
400
600
0.2 0.4 0.6 0.8
405842 G03
1 1.2
500
VCC = 5V
TA = 25°C
RPROG = 2k
PROG Pin Voltage
vs Temperature Charge Current
vs PROG Pin Voltage
4
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Regulated Output (Float) Voltage
vs Charge Current
I
BAT
(mA)
0
V
FLOAT
(V)
4.24
300
405842 G04
4.18
4.14
100 200 400
4.12
4.10
4.26
4.22
4.20
4.16
500 600 700
V
CC
= 5V
T
A
= 25°C
R
PROG
= 1.25k
Regulated Output (Float) Voltage
vs Temperature
TEMPERATURE (°C)
–50
4.185
V
FLOAT
(V)
4.190
4.195
4.200
4.205
4.215
–25 02550
405842 G05
75 100
4.210
V
CC
= 5V
R
PROG
= 10k
Regulated Output (Float) Voltage
vs Supply Voltage
V
CC
(V)
4
4.185
V
FLOAT
(V)
4.190
4.195
4.200
4.205
4.215
4.5 5 5.5 6
405842 G06
6.5 7
4.210
T
A
= 25°C
R
PROG
= 10k
CHRG Pin I-V Curve
(Pull-Down State) Trickle Charge Current
vs Temperature
ACPR Pin I-V Curve
(Pull-Down State)
V
CHRG
(V)
0
I
CHRG
(mA)
20
25
30
35
405842 G07
15
10
12 467
5
0
T
A
= –40°CT
A
= 25°C
T
A
= 90°C
V
CC
= 5V
V
BAT
= V
BSENSE
= 4V
V
ACPR
(V)
0
I
ACPR
(mA)
20
25
30
35
405842 G08
15
10
12 467
5
0
T
A
= –40°CT
A
= 25°C
T
A
= 90°C
V
CC
= 5V
V
BAT
= V
BSENSE
= 4V
TEMPERATURE (°C)
–50
0
ITRKL (mA)
10
20
30
40
60
–25 02550
405842 G09
75 100
50
VCC = 5V
VBAT = VBSENSE = 2.5V
RPROG = 2k
RPROG = 10k
Trickle Charge Current
vs Supply Voltage Charge Current vs Battery Voltage
VCC (V)
4
0
ITRKL (mA)
10
20
30
40
60
4.5 5 5.5 6
405842 G10
6.5 7
50
VBAT = VBSENSE = 2.5V
TA = 25°C
RPROG = 2k
RPROG = 10k
Trickle Charge Threshold Voltage
vs Temperature
TEMPERATURE (°C)
–50
V
TRKL
(V)
2.875
2.900
2.925
25 75
405842 G11
2.850
2.825
2.800 –25 0 50
2.950
2.975
3.000
100
V
CC
= 5V
R
PROG
= 10k
V
BAT
(V)
2.4
I
BAT
(mA)
400
500
600
3.3 3.9
405842 G08
300
200
2.7 3 3.6 4.2 4.5
100
0
V
CC
= 5V
θ
JA
= 40°C/W
R
PROG
= 2k
5
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Charge Current vs Supply Voltage Charge Current
vs Ambient Temperature Recharge Threshold Voltage
vs Temperature
Power FET Transistor Curve Power FET “ON” Resistance
vs Temperature
V
CC
(V)
4
0
I
BAT
(mA)
100
200
300
400
600
4.5 5 5.5 6
405842 G13
6.5 7
500
V
BAT
= V
BSENSE
= 4V
T
A
= 25°C
θ
JA
= 40°C/W
R
PROG
= 2k
R
PROG
= 10k
TEMPERATURE (°C)
–50
I
BAT
(mA)
400
500
600
25 75
405842 G14
300
200
–25 0 50 100 125
100
0
V
CC
= 5V
V
BAT
= V
BSENSE
= 4V
θ
JA
= 40°C/W
R
PROG
= 2k
ONSET OF THERMAL REGULATION
R
PROG
= 10k
TEMPERATURE (°C)
–50
4.04
V
RECHRG
(V)
4.06
4.08
4.10
4.12
4.16
–25 02550
405842 G15
75 100
4.14
V
CC
= 5V
R
PROG
= 10k
V
BAT
(V)
3.8
I
BAT
(mA)
300
400
500
4.7 5.3
405842 G16
200
100
04.1 4.4 5
600
700
800 V
CC
= 5V
V
BSENSE
= 3.5V
T
A
= 25°C
R
PROG
= 2k
TEMPERATURE (°C)
–50
300
R
DS(ON)
(mΩ)
400
500
600
700
800
–25 02550
405842 G17
75 100
V
CC
= 5V
V
BAT
= 4.8V
V
BSENSE
= 4V
R
PROG
= 2k
UU
U
PI FU CTIO S
BSENSE (Pin 1): Battery Sense. This pin is used to Kelvin
sense the positive battery terminal and regulate the final
float voltage to 4.2V. An internal precision resistor divider
sets this float voltage and is disconnected in shutdown
mode. For Li-Ion applications, this pin must be electri-
cally connected to BAT.
BAT (Pin 2): Charge Current Output. Provides charge
current to the battery from the internal P-channel MOSFET.
CHRG (Pin 3): Charge Status Open-Drain Output. When
the battery is charging, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the charge cycle is
completed, CHRG becomes high impedance.
GND (Pins 4, 9): Ground/Exposed Pad. The exposed
backside of the package (Pin 9) is also ground and must
be soldered to the PC board for maximum heat transfer.
PROG (Pin 5): Charge Current Program and Charge Cur-
rent Monitor. Charge current is programmed by connect-
ing a 1% resistor, R
PROG
, to ground. When charging in
constant-current mode, this pin servos to 1V. In all modes,
6
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
UU
U
PI FU CTIO S
the voltage on this pin can be used to measure the charge
current using the following formula:
I
BAT
= (V
PROG
/R
PROG
) • 1000
This pin is clamped to approximately 2.4V. Driving this pin
to voltages beyond the clamp voltage can draw currents as
high as 1.5mA.
V
CC
(Pin 6): Positive Input Supply Voltage. Provides
power to the charger. V
CC
can range from 4.25V to 6.5V.
This pin should be bypassed with at least a 1µF capacitor.
When V
CC
is within 100mV of the BSENSE pin voltage, the
LTC4058 enters shutdown mode dropping the battery
drain current to less than 2µA.
ACPR (Pin 7): Power Supply Status Open-Drain Output.
When V
CC
is greater than the undervoltage lockout thresh-
old and at least 100mV above V
BSENSE
, the ACPR pin is
pulled to ground; otherwise, the pin is high impedance.
EN (Pin 8): Enable Input . A logic high on the EN pin will put
the LTC4058 into shutdown mode where the battery drain
current is reduced to less than 2µA and the supply current
is reduced to less than 50µA. A logic low or floating the EN
pin (allowing an internal 2MΩ pull-down resistor to pull
this pin low) enables charging.
BLOCK DIAGRA
W
–
+
–
+
–
+
2
6
–
+
120°C
TDIE
TA
MA
CA
C1
1×1000×
VA
R1
BAT
1
BSENSE
R2
R3
1V
0.1V
R4
R5
PROG
TRICKLE CHARGE
DISABLED ON THE
LTC4058X
5µA
RPROG
REN
REF
1.21V
VCC
CHRG
3
EN
8
GND
4, 9
405842 BD
–
+
C2
2.9V TO BAT
TERM
ACPRCHARGE
SHDNEN
LOGIC
ACPR
7
5
7
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
OPERATIO
U
The LTC4058 is a single cell lithium-ion battery charger
using a constant-current/constant-voltage algorithm. It
can deliver up to 950mA of charge current (using a good
thermal PCB layout) with a final float voltage accuracy of
±1%. The LTC4058 includes an internal P-channel power
MOSFET and thermal regulation circuitry. No blocking
diode or external current sense resistor is required; thus,
the basic charger circuit requires only two external com-
ponents. Furthermore, the LTC4058 is capable of operat-
ing from a USB power source.
Normal Charge Cycle
A charge cycle begins when the voltage at the V
CC
pin rises
above the UVLO threshold level and a 1% program resistor
is connected from the PROG pin to ground. If the BSENSE
pin is less than 2.9V, the charger enters trickle charge mode.
In this mode, the LTC4058 supplies approximately 1/10th
the programmed charge current to bring the battery volt-
age up to a safe level for full current charging. (Note: The
LTC4058X does not include this trickle charge feature.)
When the BSENSE pin voltage rises above 2.9V, the charger
enters constant-current mode where the programmed
charge current is supplied to the battery. When the BSENSE
pin approaches the final float voltage (4.2V), the LTC4058
enters constant-voltage mode and the charge current be-
gins to decrease. When the charge current drops to 1/10th
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 charge current out of
the BAT pin is 1000 times the current out of the PROG pin.
The program resistor and the charge current are calcu-
lated using the following equations:
RV
IIV
R
PROG CHG CHG PROG
==
1000 1000
,
Charge current out of the BAT pin can be determined at any
time by monitoring the PROG pin voltage and using the
following equation:
IV
R
BAT PROG
PROG
=•1000
Charge Termination
The charge cycle terminates when the charge current falls
to 10% 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 100mV
1
for longer than
t
TERM
(typically 1ms), charging is terminated. The charge
current is latched off and the LTC4058 enters standby
mode where the input supply current drops to 200µA.
(Note: C/10 termination is disabled in trickle charging and
thermal limiting modes.)
When charging, transient loads on the BAT pin can cause
the PROG pin to fall below 100mV for short periods of time
before the DC charge current has dropped to 10% of the
programmed value. The 1ms filter time (t
TERM
) 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 10%
of the programmed value, the LTC4058 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.
The LTC4058 constantly monitors the BAT pin voltage in
standby mode. If this voltage drops below the 4.1V recharge
threshold (V
RECHRG
), another charge cycle begins and
charge current is once again supplied to the battery. To
manually restart a charge cycle when in standby mode, the
input voltage must be removed and reapplied or the charger
must be shut down and restarted using the EN pin. Figure␣ 1
shows the state diagram of a typical charge cycle.
Charge Status Indicator (CHRG)
The charge status output has two states: pull-down and
high impedance. The pull-down state indicates that the
LTC4058 is in a charge cycle. Once the charge cycle has
terminated or the LTC4058 is disabled, the pin state
becomes high impedance.
1
Any external sources that hold the PROG pin above 100mV will prevent the LTC4058 from
terminating a charge cycle.
8
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
OPERATIO
U
Power Supply Status Indicator (ACPR)
The power supply status output has two states: pull-down
and high impedance. The pull-down state indicates that
V
CC
is above the UVLO threshold (3.8V) and is also 100mV
above the battery voltage. When these conditions are not
met, the ACPR pin is high impedance indicating that the
LTC4058 is unable to charge the battery.
Thermal Limiting
An internal thermal feedback loop reduces the programmed
charge current if the die temperature attempts to rise above
a preset value of approximately 120°C. This feature protects
the LTC4058 from excessive temperature and allows the
user to push the limits of the power handling capability of
a given circuit board without risk of damaging the LTC4058.
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. DFN power considerations are discussed fur-
ther in the Applications Information section.
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in shutdown mode until V
CC
rises above the undervoltage lockout threshold. The UVLO
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 V
CC
falls to within 30mV of the BSENSE voltage. If the UVLO
comparator is tripped, the charger will not come out of
shutdown mode until V
CC
rises 100mV above the BSENSE
voltage.
Manual Shutdown
At any point in the charge cycle, the LTC4058 can be put
into shutdown mode by driving the EN pin high. This
reduces the battery drain current to less than 2µA and the
supply current to less than 50µA. When in shutdown
mode, the CHRG pin is in the high impedance state. A new
charge cycle can be initiated by driving the EN pin low. A
resistor pull-down on this pin forces the LTC4058 to be
enabled if the pin is allowed to float.
Automatic Recharge
Once the charge cycle is terminated, the LTC4058 continu-
ously monitors the voltage on the BSENSE pin using a
comparator with a 2ms filter time (t
RECHARGE
). A charge
cycle restarts when the battery voltage falls below 4.10V
(which corresponds to approximately 80% to 90% 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. The CHRG output enters
a pull-down state during recharge cycles.
Figure 1. State Diagram of a Typical Charge Cycle
TRICKLE CHARGE
MODE
1/10TH FULL CURRENT
BSENSE > 2.9V
BSENSE < 2.9V
BSENSE > 2.9V
CHRG: STRONG
PULL-DOWN
CHARGE MODE
FULL CURRENT
CHRG: STRONG
PULL-DOWN
SHUTDOWN MODE
CHRG: Hi-Z
EN DRIVEN LOW
OR
UVLO CONDITION
STOPS
EN DRIVEN HIGH
OR
UVLO CONDITION
I
CC
DROPS TO <25µA
POWER ON
PROG < 100mV
STANDBY MODE
NO CHARGE CURRENT
CHRG: Hi-Z
2.9V < BSENSE < 4.1V
405842 F01
9
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
APPLICATIO S I FOR ATIO
WUUU
Kelvin Sensing the Battery (BSENSE Pin)
The internal P-channel MOSFET drain is connected to the
BAT pin, while the BSENSE pin connects through an inter-
nal precision resistor divider to the input of the constant-
voltage amplifier. This architecture allows the BSENSE pin
to Kelvin sense the positive battery terminal. This is espe-
cially useful when the copper trace from the BAT pin to the
Li-Ion battery is long and has a high resistance. High
charge currents can cause a significant voltage drop be-
tween the positive battery terminal and the BAT pin. In this
situation, a separate trace from the BSENSE pin to the
battery terminals will eliminate this voltage error and re-
sult in more accurate battery voltage sensing. The BSENSE
pin MUST be electrically connected to the BAT pin.
Stability Considerations
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 on the BAT pin is recommended to reduce ripple
voltage. When using high value, low ESR ceramic capaci-
tors, it is recommended 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, C
PROG
, the
following equation can be used to calculate the maximum
resistance value for R
PROG
:
RC
PROG PROG
≤π1
210
5
••
Average, rather than instantaneous charge current may be
of interest to the user. For example, if a switching power
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.
LTC4058-4.2
GND
PROG
R
PROG
10k
C
FILTER
405842 F02
CHARGE
CURRENT
MONITOR
CIRCUITRY
Figure 2. Isolating Capacitive Load on PROG Pin and Filtering
Power Dissipation
It is not necessary to design for worst-case power dissi-
pation scenarios because the LTC4058 automatically re-
duces the charge current during high power conditions.
The conditions that cause the LTC4058 to reduce charge
current through thermal feedback can be approximated by
considering the power dissipated in the IC. Nearly all of
this power dissipation is generated by the internal
MOSFET—this is calculated to be approximately:
P
D
= (V
CC
– V
BAT
) • I
BAT
where P
D
is the power dissipated, V
CC
is the input supply
voltage, V
BAT
is the battery voltage and I
BAT
is the charge
current. The approximate ambient temperature at which
the thermal feedback begins to protect the IC is:
T
A
= 120°C – P
D
θ
JA
T
A
= 120°C – (V
CC
– V
BAT
) • I
BAT
• θ
JA
Example: An LTC4058 operating from a 5V supply is
programmed to supply 800mA full-scale current to a
discharged Li-Ion battery with a voltage of 3.3V. Assuming
θ
JA
is 50°C/W (see Thermal Considerations), the ambient
temperature at which the LTC4058 will begin to reduce the
charge current is approximately:
T
A
= 120°C – (5V – 3.3V) • (800mA) • 50°C/W
T
A
= 120°C – 1.36W • 50°C/W = 120°C – 68°C
T
A
= 52°C
10
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
The LTC4058 can be used above 52°C ambient but the
charge current will be reduced from 800mA. The approxi-
mate current at a given ambient temperature can be
approximated by:
ICT
VV
BAT A
CC BAT JA
=°
()
120 –
–•θ
Using the previous example with an ambient temperature
of 60°C, the charge current will be reduced to
approximately:
ICC
VV CW
C
CA
ImA
BAT
BAT
=°°
()
°=°
°
=
120 60
53350
60
85
706
–
–. • / /
Moreover, when thermal feedback reduces the charge cur-
rent the voltage at the PROG pin is also reduced proportion-
ally as discussed in the Operation section. It is important
to remember that LTC4058 applications do not need to be
designed for worst-case thermal conditions since the IC will
automatically reduce power dissipation when the junction
temperature reaches approximately 120°C.
Thermal Considerations
I
n order to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4058 package is soldered to the PC
board ground. Correctly soldered to a 2500mm
2
double-
sided 1oz copper board, the LTC4058 has a thermal
resistance of approximately 40°C/W. Failure to make
thermal contact between the exposed pad on the back-
side of the package and the copper board will result in
thermal resistances far greater than 40°C/W. As an
example, a correctly soldered LTC4058 can deliver over
800mA to a battery from a 5V supply at room tempera-
ture. Without a backside thermal connection, this num-
ber will drop considerably.
V
CC
Bypass Capacitor
Many types of capacitors can be used for input bypassing,
however, caution must be exercised when using multilayer
APPLICATIO S I FOR ATIO
WUUU
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 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, see Application
Note 88.
Charge Current Soft-Start
The LTC4058 includes a soft-start circuit to minimize the
inrush current at the start of a charge cycle. When a charge
cycle is initiated, the charge current ramps from zero to
the 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.
USB and Wall Adapter Power
The LTC4058 allows charging from both a wall adapter
and a USB port. 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 a
Schottky diode, D1, is used to prevent USB power loss
through the 1k pull-down resistor.
Typically a wall adapter can supply more current than the
500mA-limited USB port. Therefore, an N-channel
MOSFET, MN1, and an extra 3.3k program resistor are
used to increase the charge current to 800mA when the
wall adapter is present.
+
LTC4058-4.2
BAT
BSENSE
PROG
VCC
GND
D1
5V WALL
ADAPTER
800mA ICHG
USB POWER
500mA ICHG
ICHG SYSTEM
LOAD
Li-Ion
BATTERY
MP1
1k 3.3k 2k
MN1
6
4, 9
2
1
5
405842 F03
Figure 3. Combining Wall Adapter and USB Power
11
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698)
U
PACKAGE DESCRIPTIO
3.00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
2. ALL DIMENSIONS ARE IN MILLIMETERS
3. 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
4. EXPOSED PAD SHALL BE SOLDER PLATED
0.38 ± 0.10
BOTTOM VIEW—EXPOSED PAD
1.65 ± 0.10
(2 SIDES)
0.75 ±0.05
R = 0.115
TYP
2.38 ±0.10
(2 SIDES)
14
85
PIN 1
TOP MARK
0.200 REF
0.00 – 0.05
(DD8) DFN 0203
0.28 ± 0.05
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65 ±0.05
(2 SIDES)2.15 ±0.05
0.50
BSC
0.675 ±0.05
3.5 ±0.05
PACKAGE
OUTLINE
0.28 ± 0.05 0.50 BSC
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-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
APPLICATIO S I FOR ATIO
WUUU
V
IN
V
CC
LTC4058
DRAIN-BULK
DIODE OF FET
405842 F04
Figure 4. Low Loss Input Reverse Polarity Protection
Reverse Polarity Input Voltage Protection
In some applications, protection from reverse polarity
voltage on V
CC
is desired. If the supply voltage is high
enough, a series blocking diode can be used. In other
cases, where the voltage drop must be kept low, a P-channel
MOSFET can be used (as shown in Figure 4).
12
LTC4058-4.2/LTC4058X-4.2
sn405842 405842fs
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
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with Integrated Pass Transistor in ThinSOT C/10 Indicator, Up to 800mA Charge Current
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ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO S
U
Full Featured Single Cell Li-Ion Charger
BAT
V
CC
BSENSE
CHRG
2k
58
3
7
4, 9
1
2
6
405842 TA03
1µF
4.7µF
V
IN
5V
1-CELL
Li-Ion
BATTERY
LTC4058-4.2
500mA
ACPR
EN PROG
GND
1k1k
+
Li-Ion Battery Charger with Reverse Polarity Input Protection
BAT
V
CC
BSENSE
2k
58
4, 9
1
2
6
405842 TA04
4.7µF
5V
WALL
ADAPTER
LTC4058-4.2
500mA
EN PROG
GND
1-CELL
Li-Ion
BATTERY
+
LT/TP 1103 1K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORAT ION 2003
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
USB/Wall Adapter Power Li-Ion Charger
+
LTC4058-4.2
PROG
V
CC
5V WALL
ADAPTER
USB
POWER
Li-Ion
CELL
1k 10k
2.5k
6
2
1
5
4, 9
405842 TA05
GND
1µF
100mA/
500mA
µC
BAT
BSENSE
I
BAT
