LINER LTC4058X-4.2 Standalone linear li-ion battery charger with thermal regulation in dfn Datasheet

LTC4058-4.2/LTC4058X-4.2
Standalone Linear
Li-Ion Battery Charger with
Thermal Regulation in DFN
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FEATURES
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DESCRIPTIO
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
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APPLICATIO S
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Cellular Telephones, PDAs, MP3 Players
Bluetooth Applications
The LTC®4058 is a complete constant-current/constantvoltage linear charger for single cell lithium-ion batteries.
Its DFN package and low external component count make
the LTC4058 ideally suited for portable applications. Furthermore, 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 regulates the charge current to limit the die temperature during
high power operation or high ambient temperature conditions. 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*US Patent 6,522,118
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TYPICAL APPLICATIO
Complete Charge Cycle (750mAh Battery)
700
Single Cell Li-Ion Battery Charger with Kelvin Sense
VCC
1µF
BAT
BSENSE
LTC4058-4.2
CHRG
ACPR
EN
PROG
GND
+
1-CELL
Li-Ion
BATTERY
CHARGE CURRENT (mA)
VIN
4.5V TO 6.5V
600
4.50
CONSTANT
VOLTAGE
500
4.25
400
4.00
300
3.75
3.50
200
1.65k
100
405842 TA01
0
VCC = 5V
θJA = 40°C/W
RPROG = 1.65k
TA = 25°C
BATTERY VOLTAGE (V)
600mA
4.75
CONSTANT
CURRENT
3.25
3.00
0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25
405842 TA02
TIME (HOURS)
sn405842 405842fs
1
LTC4058-4.2/LTC4058X-4.2
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ABSOLUTE
RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
Input Supply Voltage (VCC) ....................... –0.3V to 10V
PROG ............................................. – 0.3V to VCC + 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
ORDER PART
NUMBER
TOP VIEW
BSENSE 1
8
EN
BAT 2
7
ACPR
6
VCC
5
PROG
CHRG 3
9
GND 4
LTC4058EDD-4.2
LTC4058XEDD-4.2
DD PART MARKING
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
LAEV
LBDH
TJMAX = 125°C, θJA = 40°C/W (NOTE 3)
EXPOSED PAD IS GROUND (PIN 9)
MUST BE SOLDERED TO PCB
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
VCC
Input Supply Voltage
CONDITIONS
MIN
ICC
Input Supply Current
Charge Mode (Note 4), RPROG = 10k
Standby Mode (Charge Terminated)
Shutdown Mode (EN = 5V, VCC < VBSENSE
or VCC < VUV)
VFLOAT
Regulated Output (Float) Voltage
0°C ≤ TA ≤ 85°C, 4.3V < VCC < 6.5V
IBAT
BAT Pin Current
RPROG = 10k, Current Mode
RPROG = 2k, Current Mode
●
●
IBSENSE
BSENSE Pin Current (Note 5)
Standby Mode, VBSENSE = 4.2V
Shutdown Mode (EN = 5V, VCC < VBSENSE or
VCC < VUV)
Sleep Mode, VCC = 0V
●
●
●
TYP
MAX
UNITS
6.5
V
0.3
200
25
1
500
50
mA
µA
µA
4.158
4.2
4.242
93
465
100
500
107
535
mA
mA
–2.5
±1
–6
±2
µA
µA
±1
±2
µA
30
45
60
mA
4.25
●
●
●
V
ITRIKL
Trickle Charge Current
VBSENSE < VTRIKL, RPROG = 2k (Note 6)
VTRIKL
Trickle Charge Threshold Voltage
RPROG = 10k, VBSENSE Rising (Note 6)
2.8
2.9
3
VTRHYS
Trickle Charge Hysteresis Voltage
RPROG = 10k (Note 6)
60
80
110
mV
VUV
VCC Undervoltage Lockout Voltage
From VCC Low to High
●
3.7
3.8
3.92
V
VUVHYS
VCC Undervoltage Lockout Hysteresis
●
150
200
300
mV
VEN(IL)
EN Pin Input Low Voltage
●
0.4
0.7
VEN(IH)
EN Pin Input High Voltage
●
REN
EN Pin Pull-Down Resistor
●
VASD
VCC – VBSENSE Lockout Threshold
VCC from Low to High
VCC from High to Low
ITERM
C/10 Termination Current Threshold
RPROG = 10k (ICHG = 100mA) (Note 7)
RPROG = 2k (ICHG = 500mA)
VPROG
PROG Pin Voltage
RPROG = 10k, Current Mode
VCHRG
CHRG Pin Output Low Voltage
VACPR
ACPR Pin Output Low Voltage
∆VRECHRG
Recharge Battery Threshold Voltage
VFLOAT – VRECHRG, 0°C ≤ TA ≤ 85°C
V
V
0.7
1
V
1.2
2
5
MΩ
70
5
100
30
140
50
mV
mV
0.085
0.085
0.10
0.10
0.115
0.115
mA/mA
mA/mA
0.93
1
1.07
V
ICHRG = 5mA
0.35
0.6
V
IACPR = 5mA
0.35
0.6
V
100
140
mV
●
●
60
sn405842 405842fs
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LTC4058-4.2/LTC4058X-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
TLIM
Junction Temperature in Constant
Temperature Mode
120
°C
RON
Power FET “ON” Resistance
(Between VCC and BAT)
600
mΩ
tSS
Soft-Start Time
IBAT = 0 to IBAT =1000V/RPROG
tRECHARGE
Recharge Comparator Filter Time
VBSENSE High to Low
0.75
2
4.5
ms
tTERM
Termination Comparator Filter Time
IBAT Drops Below ICHG/10
400
1000
2500
µs
µs
100
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: ITERM is expressed as a fraction of measured full charge current
with indicated PROG resistor.
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.
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TYPICAL PERFOR A CE CHARACTERISTICS
PROG Pin Voltage vs Supply
Voltage (Constant Current Mode)
1.0100
VCC = 5V
VBAT = VBSENSE = 4V
TA = 25°C
RPROG = 10k
1.010
1.0075
Charge Current
vs PROG Pin Voltage
600
VCC = 5V
VBAT = VBSENSE = 4V
RPROG = 10k
VCC = 5V
TA = 25°C
RPROG = 2k
500
1.0050
VPROG (V)
VPROG (V)
1.005
1.000
0.995
400
1.0025
IBAT (mA)
1.015
PROG Pin Voltage
vs Temperature
1.0000
0.9975
300
200
0.9950
0.990
0.985
100
0.9925
4
4.5
5
5.5
VCC (V)
6
6.5
7
405842 G01
0.9900
–50
–25
0
50
25
TEMPERATURE (°C)
0
75
100
405842 G02
0
0.2
0.4
0.6
0.8
VPROG (V)
1
1.2
405842 G03
sn405842 405842fs
3
LTC4058-4.2/LTC4058X-4.2
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TYPICAL PERFOR A CE CHARACTERISTICS
Regulated Output (Float) Voltage
vs Charge Current
Regulated Output (Float) Voltage
vs Temperature
4.26
4.215
4.215
VCC = 5V
RPROG = 10k
4.210
4.16
4.205
VFLOAT (V)
4.18
TA = 25°C
RPROG = 10k
4.210
4.205
4.20
VFLOAT (V)
VFLOAT (V)
VCC = 5V
4.24 TA = 25°C
RPROG = 1.25k
4.22
Regulated Output (Float) Voltage
vs Supply Voltage
4.200
4.200
4.195
4.195
4.190
4.190
4.14
4.12
4.10
0
100
200
300 400
IBAT (mA)
500
600
4.185
–50
700
–25
75
0
25
50
TEMPERATURE (°C)
CHRG Pin I-V Curve
(Pull-Down State)
60
TA = 90°C
15
10
25
TA = 25°C
20
TA = 90°C
0
4
3
VCHRG (V)
2
5
6
7
1
4
3
VACPR (V)
2
5
405842 G07
6
3.000
2.975
RPROG = 2k
VTRKL (V)
30
Charge Current vs Battery Voltage
VCC = 5V
RPROG = 10k
500
400
2.925
2.900
300
200
6.5
7
405842 G10
2.800
–50
VCC = 5V
θJA = 40°C/W
RPROG = 2k
100
2.825
6
100
2.850
RPROG = 10k
5.5
VCC (V)
75
600
2.875
20
5
0
25
50
TEMPERATURE (°C)
2.950
40
4.5
–25
405842 G09
Trickle Charge Threshold Voltage
vs Temperature
50
4
RPROG = 10k
405842 G08
VBAT = VBSENSE = 2.5V
TA = 25°C
10
30
0
–50
7
IBAT (mA)
60
VCC = 5V
VBAT = VBSENSE = 2.5V
10
VCC = 5V
VBAT = VBSENSE = 4V
0
Trickle Charge Current
vs Supply Voltage
7
20
0
1
6.5
40
15
5
VCC = 5V
VBAT = VBSENSE = 4V
0
6
RPROG = 2k
10
5
5.5
VCC (V)
50
ITRKL (mA)
20
TA = –40°C
IACPR (mA)
ICHRG (mA)
25
TA = 25°C
5
4.5
Trickle Charge Current
vs Temperature
30
TA = –40°C
4
405842 G06
ACPR Pin I-V Curve
(Pull-Down State)
30
ITRKL (mA)
4.185
405842 G05
405842 G04
0
100
–25
0
50
25
TEMPERATURE (°C)
75
100
405842 G11
0
2.4
2.7
3
3.3 3.6
VBAT (V)
3.9
4.2
4.5
405842 G08
sn405842 405842fs
4
LTC4058-4.2/LTC4058X-4.2
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TYPICAL PERFOR A CE CHARACTERISTICS
Charge Current
vs Ambient Temperature
Charge Current vs Supply Voltage
600
Recharge Threshold Voltage
vs Temperature
4.16
600
ONSET OF THERMAL REGULATION
RPROG = 2k
500
4.14
500
VCC = 5V
RPROG = 10k
RPROG = 2k
400
VBAT = VBSENSE = 4V
TA = 25°C
θJA = 40°C/W
300
200
VCC = 5V
VBAT = VBSENSE = 4V
θJA = 40°C/W
300
RPROG = 10k
4
4.5
5
5.5
VCC (V)
RPROG = 10k
100
6
6.5
0
–50
7
–25
4.06
50
25
75
0
TEMPERATURE (°C)
405842 G13
100
4.04
–50
125
0
25
50
TEMPERATURE (°C)
–25
75
100
405842 G15
405842 G14
Power FET “ON” Resistance
vs Temperature
Power FET Transistor Curve
800
800
VCC = 5V
VBAT = 4.8V
= 4V
V
700 RBSENSE= 2k
PROG
VCC = 5V
VBSENSE = 3.5V
TA = 25°C
RPROG = 2k
700
RDS(ON) (mΩ)
600
IBAT (mA)
4.10
4.08
200
100
0
4.12
VRECHRG (V)
IBAT (mA)
IBAT (mA)
400
500
400
300
600
500
200
400
100
0
3.8
4.1
4.4
4.7
VBAT (V)
5
5.3
405842 G16
300
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
405842 G17
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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 electrically 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 Current Monitor. Charge current is programmed by connecting a 1% resistor, RPROG, to ground. When charging in
constant-current mode, this pin servos to 1V. In all modes,
sn405842 405842fs
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LTC4058-4.2/LTC4058X-4.2
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PI FU CTIO S
the voltage on this pin can be used to measure the charge
current using the following formula:
ACPR (Pin 7): Power Supply Status Open-Drain Output.
When VCC is greater than the undervoltage lockout threshold and at least 100mV above VBSENSE, the ACPR pin is
pulled to ground; otherwise, the pin is high impedance.
IBAT = (VPROG/RPROG) • 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.
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.
VCC (Pin 6): Positive Input Supply Voltage. Provides
power to the charger. VCC can range from 4.25V to 6.5V.
This pin should be bypassed with at least a 1µF capacitor.
When VCC is within 100mV of the BSENSE pin voltage, the
LTC4058 enters shutdown mode dropping the battery
drain current to less than 2µA.
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BLOCK DIAGRA
6
VCC
120°C
TA
TDIE
1×
1000×
BAT
–
+
5µA
MA
BSENSE
2
1
R1
+
ACPR
7
VA
R2
–
CHRG
CA
3
+
–
REF
1.21V
R3
1V
CHARGE ACPR
R4
LOGIC
+
TERM
0.1V
C1
R5
–
EN
SHDN
EN
TRICKLE CHARGE
DISABLED ON THE
LTC4058X
8
REN
C2
–
+
2.9V
TO BAT
PROG
5
GND
4, 9
RPROG
405842 BD
sn405842 405842fs
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LTC4058-4.2/LTC4058X-4.2
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OPERATIO
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 components. Furthermore, the LTC4058 is capable of operating from a USB power source.
Normal Charge Cycle
A charge cycle begins when the voltage at the VCC 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 voltage 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 begins 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 calculated using the following equations:
RPROG =
1000 V
1000 V
, I CHG =
ICHG
RPROG
Charge current out of the BAT pin can be determined at any
time by monitoring the PROG pin voltage and using the
following equation:
IBAT =
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 100mV1 for longer than
tTERM (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 (tTERM) on the
termination comparator ensures that transient loads of
this nature do not result in premature charge cycle termination. 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 (VRECHRG), 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.
1Any external sources that hold the PROG pin above 100mV will prevent the LTC4058 from
terminating a charge cycle.
VPROG
• 1000
RPROG
sn405842 405842fs
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LTC4058-4.2/LTC4058X-4.2
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OPERATIO
POWER ON
BSENSE < 2.9V
TRICKLE CHARGE
MODE
EN DRIVEN LOW
OR
UVLO CONDITION
STOPS
charger will automatically reduce the current in worst-case
conditions. DFN power considerations are discussed further in the Applications Information section.
1/10TH FULL CURRENT
Undervoltage Lockout (UVLO)
CHRG: STRONG
PULL-DOWN
BSENSE > 2.9V
SHUTDOWN MODE
CHARGE MODE
ICC DROPS TO <25µA
FULL CURRENT
CHRG: Hi-Z
BSENSE > 2.9V
CHRG: STRONG
PULL-DOWN
PROG < 100mV
STANDBY MODE
NO CHARGE CURRENT
EN DRIVEN HIGH
OR
UVLO CONDITION
CHRG: Hi-Z
405842 F01
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in shutdown mode until VCC
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 VCC
falls to within 30mV of the BSENSE voltage. If the UVLO
comparator is tripped, the charger will not come out of
shutdown mode until VCC rises 100mV above the BSENSE
voltage.
2.9V < BSENSE < 4.1V
Figure 1. State Diagram of a Typical Charge Cycle
Manual Shutdown
The power supply status output has two states: pull-down
and high impedance. The pull-down state indicates that
VCC 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.
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.
Thermal Limiting
Automatic Recharge
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
Once the charge cycle is terminated, the LTC4058 continuously monitors the voltage on the BSENSE pin using a
comparator with a 2ms filter time (tRECHARGE). 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.
Power Supply Status Indicator (ACPR)
sn405842 405842fs
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LTC4058-4.2/LTC4058X-4.2
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APPLICATIO S I FOR ATIO
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 internal precision resistor divider to the input of the constantvoltage amplifier. This architecture allows the BSENSE pin
to Kelvin sense the positive battery terminal. This is especially 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 between 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 result 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 without 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 capacitors, 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; 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, CPROG, the
following equation can be used to calculate the maximum
resistance value for RPROG:
RPROG ≤
1
2π • 105 • CPROG
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
10k
PROG
GND
RPROG
CFILTER
CHARGE
CURRENT
MONITOR
CIRCUITRY
405842 F02
Figure 2. Isolating Capacitive Load on PROG Pin and Filtering
Power Dissipation
It is not necessary to design for worst-case power dissipation scenarios because the LTC4058 automatically reduces 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:
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:
TA = 120°C – PDθJA
TA = 120°C – (VCC – VBAT) • IBAT • θJA
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
θJA is 50°C/W (see Thermal Considerations), the ambient
temperature at which the LTC4058 will begin to reduce the
charge current is approximately:
TA = 120°C – (5V – 3.3V) • (800mA) • 50°C/W
TA = 120°C – 1.36W • 50°C/W = 120°C – 68°C
TA = 52°C
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9
LTC4058-4.2/LTC4058X-4.2
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APPLICATIO S I FOR ATIO
The LTC4058 can be used above 52°C ambient but the
charge current will be reduced from 800mA. The approximate current at a given ambient temperature can be
approximated by:
IBAT =
120°C – TA
( VCC – VBAT ) • θJA
Using the previous example with an ambient temperature
of 60°C, the charge current will be reduced to
approximately:
IBAT
120°C – 60°C
60°C
=
=
(5V – 3.3V) • 50°C/W 85°C/A
IBAT = 706mA
Moreover, when thermal feedback reduces the charge current the voltage at the PROG pin is also reduced proportionally 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
In 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 2500mm2 doublesided 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 backside 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 temperature. Without a backside thermal connection, this number will drop considerably.
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.
5V WALL
ADAPTER
800mA ICHG
USB POWER
500mA ICHG
LTC4058-4.2
2
BAT
1
6
VCC BSENSE
5
4, 9
GND PROG
MP1
3.3k
1k
VCC Bypass Capacitor
Many types of capacitors can be used for input bypassing,
however, caution must be exercised when using multilayer
ICHG
D1
MN1
+
SYSTEM
LOAD
Li-Ion
BATTERY
2k
405842 F03
Figure 3. Combining Wall Adapter and USB Power
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10
LTC4058-4.2/LTC4058X-4.2
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APPLICATIO S I FOR ATIO
Reverse Polarity Input Voltage Protection
DRAIN-BULK
DIODE OF FET
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, where the voltage drop must be kept low, a P-channel
MOSFET can be used (as shown in Figure 4).
LTC4058
VCC
VIN
405842 F04
Figure 4. Low Loss Input Reverse Polarity Protection
U
PACKAGE DESCRIPTIO
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 ±0.05
3.5 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.28 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
TYP
5
3.00 ±0.10
(4 SIDES)
0.38 ± 0.10
8
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(DD8) DFN 0203
0.200 REF
0.75 ±0.05
0.00 – 0.05
4
0.28 ± 0.05
1
0.50 BSC
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
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
sn405842 405842fs
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LTC4058-4.2/LTC4058X-4.2
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TYPICAL APPLICATIO S
Full Featured Single Cell Li-Ion Charger
Li-Ion Battery Charger with Reverse Polarity Input Protection
VIN
5V
1k
4.7µF
1k
5V
WALL
ADAPTER
6
VCC
2
7
ACPR
BAT
1
3
CHRG BSENSE
LTC4058-4.2
8
5
EN
PROG
GND
6
VCC
500mA
+
4.7µF
1-CELL
Li-Ion
BATTERY
1µF
2k
500mA
2
BAT
1
BSENSE
LTC4058-4.2
8
5
EN
PROG
GND
+
1-CELL
Li-Ion
BATTERY
2k
4, 9
4, 9
405842 TA04
405842 TA03
USB/Wall Adapter Power Li-Ion Charger
IBAT
2
BAT
1
BSENSE
5V WALL
ADAPTER
+
LTC4058-4.2
6
USB
POWER
VCC
1µF
1k
5
PROG
GND
4, 9 10k
Li-Ion
CELL
2.5k
100mA/
500mA
µC
405842 TA05
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1732
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Simple Charger uses External FET, Features Preset Voltages, C/10
Charger Detection and Programmable Timer, Input Power Good Indication
LTC1733
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Standalone Charger with Programmable Timer, Up to 1.5A Charge Current
TM
LTC1734
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Low Current Version of LTC1734; 50mA ≤ ICHRG ≤ 180mA
LTC1998
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1% Accurate 2.5µA Quiescent Current, SOT-23
LTC4007
4A Multicell Li-Ion Battery Charger
Standalone Charger, 6V ≤ VIN ≤ 28V, Up to 96% Efficiency,
±0.8% Charging Voltage Accuracy
LTC4050
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Features Preset Voltages, C/10 Charger Detection and Programmable Timer,
Input Power Good Indication, Thermistor Interface
LTC4052
Monolithic Lithium-Ion Battery Pulse Charger
No Blocking Diode or External Power FET Required, ≤1.5A Charge Current
LTC4053
USB Compatible Monolithic Li-Ion Battery Charger
Standalone Charger with Programmable Timer, Up to 1.25A Charge Current
LTC4054
Standalone Linear Li-Ion Battery Charger
with Integrated Pass Transistor in ThinSOT
Thermal Regulation Prevents Overheating, C/10 Termination,
C/10 Indicator, Up to 800mA Charge Current
LTC4057
Li-Ion Linear Battery Charger
Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package
LTC4410
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
LTC4412
Low Loss PowerPathTM Controller in ThinSOT
Automatic Switching Between DC Sources, Load Sharing,
Replaces ORing Diodes
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
sn405842 405842fs
12
Linear Technology Corporation
LT/TP 1103 1K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2003