LTC4059/LTC4059A
1
4059fb
■
Wireless PDAs
■
Cellular Phones
■
Portable Electronics
■
Wireless Headsets
■
Digital Cameras
■
Programmable Charge Current Up to 900mA
■
Charge Current Monitor Output for Charge
Termination
■
Constant-Current/Constant-Voltage Operation with
Thermal Regulation to Maximize Charging Rate
Without Risk of Overheating
■
Constant-Current Source Mode for Charging
Nickel Batteries (LTC4059 Only)
■
ACPR Pin Indicates Presence of Input Supply
(LTC4059A Only)
■
No External MOSFET, Sense Resistor or Blocking
Diode Required
■
Operating Supply Voltage from 3.75V to 8V
■
Charges Single Cell Li-Ion Batteries Directly from
USB Port
■
Preset 4.2V Charge Voltage with 0.6% Accuracy
■
10µA Supply Current in Shutdown Mode
■
Tiny 6-Lead (2mm × 2mm) DFN Package
900mA Linear Li-Ion
Battery Chargers with
Thermal Regulation in 2 × 2 DFN
The LTC
®
4059/LTC4059A are constant-current/constant-
voltage linear chargers for single cell lithium-ion batteries.
Their 2mm × 2mm DFN package and low external compo-
nent count make these chargers especially well suited for
portable applications. Furthermore, they are designed to
work within USB power specifications.
No external sense resistor, MOSFET or blocking diode is
required. Thermal feedback regulates the charge current
to limit the die temperature during high power operation or
high ambient thermal conditions. The charge voltage is
fixed at 4.2V and the charge current is programmable.
When the input supply (wall adapter or USB supply) is
removed, the LTC4059/LTC4059A automatically enter a low
current state, dropping the battery current drain to less than
1µA. With power applied, they can be put into shutdown
mode, reducing the supply current to 10µA.
The LTC4059A features an open-drain status pin to indi-
cate the presence of an input voltage. The LTC4059 can be
used as a constant-current source to charge Nickel cells.
Other features include undervoltage lockout protection
and a current monitor pin which can indicate when to
terminate a charge cycle.
The LTC4059/LTC4059A are available in a 6-lead, low
profile (0.75mm) 2mm × 2mm DFN package.
Complete Charge Cycle (800mAh Battery)
TIME (HOURS)
0
500
600
700
2
4059 TA02
400
300
0.5 1 1.5 2.5
200
100
0
4.0
4.2
4.4
3.8
3.6
3.4
3.2
3.0
CHARGE CURRENT (mA)
BATTERY VOLTAGE (V)
CONSTANT
CURRENT
CONSTANT
VOLTAGE
V
CC
= 5V
R
PROG
= 2k
T
A
= 25°C
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
V
CC
LTC4059A
V
IN
4.5V TO 8V
EN
GND
BAT
1µF
2k
50k
4.2V
Li-Ion
BATTERY
600mA
V
DD
µP
4059 TA01
ACPR
PROG
+
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6522118.
LTC4059/LTC4059A
2
4059fb
Input Supply Voltage (V
CC
) ...................... –0.3V to 10V
BAT, PROG, EN, Li CC, ACPR ................... –0.3V to 10V
BAT Short-Circuit Duration ...........................Continuous
BAT Pin Current ............................................... 1000mA
PROG Pin Current ............................................. 1000µA
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
Consult LTC Marketing for parts specified with wider operating temperature ranges.
LTC4059EDC
LTC4059AEDC
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
T
JMAX
= 125°C, θ
JA
= 60°C/W TO 85°C/W (NOTE 3)
*Li CC PIN 2 ON LTC4059EDC,
ACPR PIN 2 ON LTC4059AEDC
EXPOSED PAD (PIN 7) IS GND
MUST BE SOLDERED TO PCB
TOP VIEW
7
DC6 PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
4
5
6
3
2
1GND
BAT
EN
PROG
V
CC
Li CC/ACPR*
DC6 PART
MARKING
LAFU
LBJH
ELECTRICAL CHARACTERISTICS
The ● denotes the 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
V
CC
V
CC
Supply Voltage ●3.75 8 V
I
CC
Quiescent V
CC
Supply Current V
BAT
= 4.5V (Forces I
BAT
and I
PROG
= 0) ●25 60 µA
I
CCMS
V
CC
Supply Current in Shutdown V
EN
= V
CC
●10 25 µA
I
CCUV
V
CC
Supply Current in Undervoltage V
CC
< V
BAT
; V
CC
= 3.5V, V
BAT
= 4V ●410 µA
Lockout
V
FLOAT
V
BAT
Regulated Output Voltage I
BAT
= 2mA 4.175 4.2 4.225 V
4.5V < V
CC
< 8V, I
BAT
= 2mA ●4.158 4.2 4.242 V
I
BAT
BAT Pin Current R
PROG
= 2.43k, Current Mode, V
BAT
= 3.8V ●475 500 525 mA
R
PROG
= 12.1k, Current Mode, V
BAT
= 3.8V ●94 100 106 mA
I
BMS
Battery Drain Current in Shutdown V
EN
= V
CC
, V
CC
> V
BAT
●0±1µA
I
BUV
Battery Drain Current in Undervoltage V
CC
< V
BAT
, V
BAT
= 4V ●014 µA
Lockout
V
UV
V
CC
– V
BAT
Undervoltage Lockout V
CC
from Low to High, V
BAT
= 3.7V ●100 150 200 mV
Threshold V
CC
from High to Low, V
BAT
= 3.7V ●03580 mV
V
PROG
PROG Pin Voltage R
PROG
= 2.43k, I
PROG
= 500µA●1.18 1.21 1.24 V
R
PROG
= 12.1k, I
PROG
= 100µA●1.18 1.21 1.24 V
V
MS
Manual Shutdown Threshold V
EN
Increasing ●0.3 0.92 1.2 V
V
MSHYS
Manual Shutdown Hysteresis V
EN
Decreasing 85 mV
R
EN
EN Pin Input Resistance V
EN
= 5V ●1 1.85 3 MΩ
V
Li CC
Voltage Mode Disable Threshold V
Li CC
Increasing (LTC4059 Only) ●0.3 0.92 1.2 V
V
Li CCHYS
Voltage Mode Disable Hysteresis V
Li CC
Decreasing (LTC4059 Only) 85 mV
V
ACPR
ACPR Pin Output Low Voltage I
ACPR
= 300µA (LTC4059A Only) 0.25 0.5 V
t
LIM
Junction Temperature In Constant 115 °C
Temperature Mode
R
ON
Power FET “ON” Resistance I
BAT
= 150mA (Note 4) 800 1200 mΩ
(Between V
CC
and BAT)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC4059E/LTC4059AE 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 ground plane will result in a thermal resistance much higher than
60°C/W.
Note 4: The FET on-resistance is guaranteed by correlation to wafer level
measurements.
LTC4059/LTC4059A
3
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TYPICAL PERFOR A CE CHARACTERISTICS
UW
Battery Regulation (Float) Voltage
vs Battery Charge Current
I
BAT
(mA)
0
V
FLOAT
(V)
4.16
4.18
4.20
300 500
4059 G01
4.14
4.12
4.10 100 200 400
4.22
4.24
4.26 V
CC
= 5V
T
A
= 25°C
R
PROG
= 2.43k
TEMPERATURE (°C)
–50
V
FLOAT
(V)
4.19
4.20
4.21
25 75
4059 G02
4.18
4.17
4.16 –25 0 50
4.22
4.23
4.24
100
V
CC
= 5V
I
BAT
= 2mA
R
PROG
= 2.43k
V
CC
(V)
4
V
FLOAT
(V)
4.19
4.20
4.21
7
4059 G03
4.18
4.17
4.16 56
4.22
4.23
4.24
8
T
A
= 25°C
I
BAT
= 10mA
R
PROG
= 2.43k
Battery Regulation (Float) Voltage
vs Temperature
Regulated Output (Float) Voltage
vs Supply Voltage
Charge Current vs Input Voltage
Charge Current vs Ambient
Temperature with Thermal
Regulation
V
CC
(V)
4
0
I
BAT
(mA)
100
200
300
400
500
600
56 78
4059 G04
V
BAT
= 3.85V
T
A
= 25°C
THERMAL
LIMITING
R
PROG
= 2.43k
R
PROG
= 12.1k
Charge Current vs Battery Voltage
V
BAT
(V)
2.5
0
I
BAT
(mA)
100
200
300
400
500
600
3 3.5 4 4.5
4059 G05
Li CC = 5V
LTC4059 ONLY
Li CC = 0V
LTC4059A
V
CC
= 5V
T
A
= 25°C
R
PROG
= 2.43k
AMBIENT TEMPERATURE (°C)
–50
I
BAT
(mA)
400
500
600
25 75
4059 G06
300
200
–25 0 50 100 125
100
0
R
PROG
= 12.1k
R
PROG
= 2.43k
V
CC
= 5V
V
BAT
= 3.85V
THERMAL CONTROL
LOOP IN OPERATION
PROG Pin Voltage vs Temperature
(Constant Current Mode)
PROG Pin Voltage
vs Charge Current
Power FET “ON” Resistance
vs Temperature
I
BAT
(mA)
0
1.0
1.2
1.4
400
4059 F07
0.8
0.6
100 200 300 500
0.4
0.2
0
V
PROG
(V)
V
CC
= 5V
T
A
= 25°C
R
PROG
= 2.43k
TEMPERATURE (°C)
–50
400
RDS(ON) (mΩ)
500
600
700
800
1200
1000
–25 02550
4059 G09
75 100
900
VCC = 5V
IBAT = 100mA
TEMPERATURE (°C)
–50
V
PROG
(V)
1.22
1.23
1.24
25 75
4059 G08
1.21
1.20
–25 0 50 100 125
1.19
1.18
R
PROG
= 12.1k
R
PROG
= 2.43k
V
CC
= 5V
V
BAT
= 3.85V
LTC4059/LTC4059A
4
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TYPICAL PERFOR A CE CHARACTERISTICS
UW
VCC – VBAT Undervoltage Lockout
Threshold vs Battery Voltage
EN Pin Current
vs EN Voltage and Temperature
UVLO Battery Drain Current
vs Battery Voltage
V
BAT
(V)
3
V
UV
(mV)
300
400
500
7
4059 G10
200
100
250
350
450
150
50
04568
T
A
= 25°C
R
PROG
= 12.1k
V
EN
(V)
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
035
4059 G11
12 46
EN (µA)
T
A
= 100°C
T
A
= –20°C
T
A
= 25°C
V
BAT
(V)
0
I
BUV
(µA)
1.2
1.6
2.0
4
4059 G12
0.8
0.4
1.0
1.4
1.8
0.6
0.2
01235
V
CC
= 0V
T
A
= 25°C
UVLO Battery Drain Current
vs Temperature
Manual Shutdown Supply Current
vs Temperature
TEMPERATURE (°C)
–50 –25
0
I
BUV
(µA)
1.0
2.5
050 75
4059 G13
0.5
2.0
1.5
25 100 125
V
CC
= 0V
V
BAT
= 4V
TEMPERATURE (°C)
–50
8
10
14
25 75
4059 G14
6
4
–25 0 50 100 125
2
0
12
I
CCMS
(µA)
V
CC
= 5V
V
EN
= 5V
Manual Shutdown Threshold
Voltage vs Temperature
Voltage Mode Disable Threshold
Voltage vs Temperature
(LTC4059 Only)
TEMPERATURE (°C)
–50
0.6
VMS (V)
0.7
0.8
0.9
1.0
1.2
–25 02550
4059 F15
75 100
1.1
RISING
FALLING
TEMPERATURE (°C)
–50
0.6
VLi CC (V)
0.7
0.8
0.9
1.0
1.2
–25 02550
4059 F16
75 100
1.1
RISING
FALLING
ACPR Pin Output Low Voltage
vs Temperature (LTC4059A Only)
TEMPERATURE (°C)
–50
V
ACPR
(V)
0.45
25
4059 G17
0.30
0.20
–25 0 50
0.15
0.10
0.50
0.40
0.35
0.25
75 100 125
V
CC
= 5V
V
BAT
= 4.2V
I
ACPR
= 300µA
V
ACPR
(V)
0
I
ACPR
(mA)
2.0
3.0
8
4059 G18
1.0
0246
1357
4.0
1.5
2.5
0.5
3.5
V
CC
= 5V
V
BAT
= 4.2V
T
A
= 25°C
ACPR Pin (Pull-Down State)
I-V Curve (LTC4059A Only)
LTC4059/LTC4059A
5
4059fb
PI FU CTIO S
UUU
GND (Pins 1, 7): Ground/Exposed Pad. The exposed
package pad is ground and must be soldered to the PC
board for maximum heat transfer.
Li CC (Pin 2, LTC4059): Li-Ion/Constant Current Input
Pin. Pulling this pin above V
Li CC
disables voltage mode
thereby providing a constant current to the BAT pin. This
feature is useful for charging Nickel chemistry batteries.
Tie to GND if unused.
ACPR (Pin 2, LTC4059A): Open-Drain Power Supply
Status Output. When V
CC
is greater than the undervoltage
lockout threshold, the ACPR pin will pull to ground;
otherwise the pin is forced to a high impedance state.
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.
V
CC
(Pin 4): Positive Input Supply Voltage. This pin
provides power to the charger. V
CC
can range from 3.75V
to 8V. This pin should be bypassed with at least a 1µF
capacitor. When V
CC
is within 35mV of the BAT pin
voltage, the LTC4059 enters shutdown mode, dropping
I
BAT
to less than 4µA.
PROG (Pin 5): Charge Current Program and Charge Cur-
rent Monitor Pin. Connecting a resistor, R
PROG
, to ground
programs the charge current. When charging in constant-
current mode, this pin servos to 1.21V. In all modes, the
voltage on this pin can be used to measure the charge
current using the following formula:
IV
R
BAT PROG
PROG
=• 1000
EN (Pin 6): Enable Input Pin. Pulling this pin above the
manual shutdown threshold (V
MS
is typically 0.92V) puts
the LTC4059 in shutdown mode, thus terminating a charge
cycle. In shutdown mode, the LTC4059 has less than 25µA
supply current and less than 1µA battery drain current.
Enable is the default state, but the pin should be tied to
GND if unused.
LTC4059/LTC4059A
6
4059fb
BLOCK DIAGRA
W
2 1,7
3
4
6
+
–
+
MA
V
CC
M2
1×
D1
M1
1000×
R1
R2
R3
D3
–
+
–+
CA
REF
TA
–
+
T
DIE
115°C
1.2V VOLTAGE
REFERENCE
VA
BAT
REF
LOGIC
R
EN
EN
D2
Li CCPROG GND
4059 F01
5
Figure 1 (LTC4059)
1,7
3
4
6
+
–
+
MA
VCC
M2
1×
D1
BAT VCC
M1
1000×
R1
R2
R3
D3
–
+
–
+
–+
CA
REF
TA
–
+
TDIE
115°C
1.2V VOLTAGE
REFERENCE
VA
BAT
REF
LOGIC
REN
EN
2ACPR
D2
PROG GND
4059 F02
5
Figure 2 (LTC4059A)
LTC4059/LTC4059A
7
4059fb
OPERATIO
U
The LTC4059/LTC4059A are linear battery chargers de-
signed primarily for charging single cell lithium-ion bat-
teries. Featuring an internal P-channel power MOSFET,
the chargers use a constant-current/constant-voltage
charge algorithm with programmable current. Charge
current can be programmed up to 900mA with a final float
voltage accuracy of ±0.6%. No blocking diode or external
sense resistor is required; thus, the basic charger circuit
requires only two external components. The ACPR pin
(LTC4059A) monitors the status of the input voltage with
an open-drain output. The Li CC pin (LTC4059) disables
constant-voltage operation and turns the LTC4059 into a
precision current source capable of charging Nickel chem-
istry batteries. Furthermore, the LTC4059/LTC4059A are
designed to operate from a USB power source.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
preset value of approximately 115°C. This feature protects
the LTC4059/LTC4059A 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 LTC4059/LTC4059A or external components. Another
benefit of the thermal limit is that charge current can be set
according to typical, not worst-case, ambient tempera-
tures for a given application with the assurance that the
charger will automatically reduce the current in worst-
case conditions.
The charge cycle begins when the voltage at the V
CC
pin
rises approximately 150mV above the BAT pin voltage, a
program resistor is connected from the PROG pin to
ground, and the EN pin is pulled below the shutdown
threshold (typically 0.92V).
If the BAT pin voltage is below 4.2V, or the Li CC pin is
pulled above V
Li CC
(LTC4059 only), the LTC4059 will
charge the battery with the programmed current. This is
constant-current mode. When the BAT pin approaches the
final float voltage (4.2V), the LTC4059 enters constant-
voltage mode and the charge current begins to decrease.
To terminate the charge cycle the EN should be pulled
above the shutdown threshold. Alternatively, reducing the
input voltage below the BAT pin voltage will also terminate
the charge cycle.
APPLICATIO S I FOR ATIO
WUUU
Programming Charge Current
The charge current is programmed using a single resistor
from the PROG pin to ground. The battery charge current
is 1000 times the current out of the PROG pin. The
program resistor and the charge current are calculated
using the following equations:
RV
IIV
R
PROG CHG CHG PROG
==1000 121 1000 121
•.,•
.
For best stability over temperature and time, 1% metal-
film resistors are recommended.
The charge current out of the BAT pin can be determined
at any time by monitoring the PROG pin voltage and using
the following equation:
IV
R
BAT PROG
PROG
=• 1000
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in undervoltage lockout until
V
CC
rises approximately 150mV above the BAT pin voltage.
The UVLO circuit has a built-in hysteresis of 115mV. If the
BAT pin voltage is below approximately 2.75V, then the
charger will remain in undervoltage lockout until V
CC
rises
above approximately 3V. During undervoltage lockout
conditions, maximum battery drain current is 4µA.
Power Supply Status Indicator
(ACPR, LTC4059A Only)
The power supply status output has two states: pull-down
and high impedance. The pull-down state indicates that
V
CC
is above the undervoltage lockout threshold (see
Undervoltage Lockout). When this condition is not met,
the ACPR pin is high impedance indicating that the
LTC4059A is unable to charge the battery.
LTC4059/LTC4059A
8
4059fb
Shutdown Mode
Charging can be terminated by pulling the EN pin above the
shutdown threshold (approximately 0.92V). In shutdown
mode, the battery drain current is reduced to less than 1µA
and the supply current to 10µA.
USB and Wall Adapter Power
Although the LTC4059
/LTC4059A
allow charging from a
USB port, a wall adapter can also be used to charge Li-Ion
batteries. Figure 3 shows an example of how to combine
wall adapter and USB power inputs. A P-channel MOSFET,
MP1, is used to prevent back conducting into the USB port
when a wall adapter is present and Schottky diode, D1, is
used to prevent USB power loss through the 1k pull-down
resistor.
Typically a wall adapter can supply significantly more
current than the 500mA limited USB port. Therefore, an
N-channel MOSFET, MN1, and an extra program resistor
are used to increase the charge current to 850mA when the
wall adapter is present.
ance of the current source pair, M1 and M2 (note that M1
is the internal P-channel power MOSFET). It ensures that
the drain current of M1 is exactly 1000 times greater than
the drain current of M2.
Amplifiers CA and VA are used in separate feedback loops
to force the charger into constant-current or voltage
mode, respectively. Diodes D1 and D2 provide priority to
either the constant-current or constant-voltage loop;
whichever is trying to reduce the charge current the most.
The output of the other amplifier saturates low which
effectively removes its loop from the system. When in
constant-current mode, CA servos the voltage at the
PROG pin to be 1.21V. VA servos its inverting input to
precisely 1.21V when in constant-voltage mode and the
internal resistor divider made up of R1 and R2 ensures
that the battery voltage is maintained at 4.2V. The PROG
pin voltage gives an indication of the charge current
during constant-voltage mode as discussed in the Pro-
gramming Charge Current section.
Transconductance amplifier, TA, limits the die tempera-
ture to approximately 115°C when in constant-tempera-
ture mode. TA acts in conjunction with the constant-current
loop. When the die temperature exceeds approximately
115°C, TA sources current through R3. This causes CA to
reduce the charge current until the PROG pin voltage plus
the voltage across R3 equals 1.21V. Diode D3 ensures that
TA does not affect the charge current when the die tem-
perature is below approximately 115°C. The PROG pin
voltage continues to give an indication of the charge
current.
In typical operation, the charge cycle begins in constant-
current mode with the current delivered to the battery
equal to 1210V/R
PROG
. If the power dissipation of the
LTC4059
/LTC4059A
results in the junction temperature
approaching 115°C, the amplifier (TA) will begin decreas-
ing the charge current to limit the die temperature to
approximately 115°C. As the battery voltage rises, the
LTC4059
/LTC4059A
either return to constant-current mode
or enter constant-voltage mode straight from constant-
temperature mode. Regardless of mode, the voltage at the
PROG pin is proportional to the current delivered to the
battery.
APPLICATIO S I FOR ATIO
WUUU
Figure 3. Combining Wall Adapter and USB Power
BAT
LTC4059
3.4k 2.43k1k MN1
MP1
5V WALL
ADAPTER
850mA I
CHG
USB
POWER
500mA I
CHG
I
CHG
V
CC
3
D1
4
5Li-Ion
BATTERY
4059 F03
SYSTEM
LOAD
PROG
+
Constant Current/Constant Voltage/
Constant Temperature
The LTC4059
/LTC4059A
use a unique architecture to
charge a battery in a constant-current, constant-voltage
and constant-temperature fashion. Figures 1 and 2 show
simplified block diagrams of the LTC4059 and LTC4059A
respectively. Three of the amplifier feedback loops shown
control the constant-current, CA, constant-voltage, VA,
and constant-temperature, TA modes. A fourth amplifier
feedback loop, MA, is used to increase the output imped-
LTC4059/LTC4059A
9
4059fb
Power Dissipation
The conditions that cause the LTC4059
/LTC4059A
to
reduce charge current through thermal feedback can be
approximated by considering the power dissipated in the
IC. For high charge currents, the LTC4059 power dissipa-
tion is 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. It is not necessary to perform any worst-case
power dissipation scenarios because the LTC4059
/
LTC4059A
will automatically reduce the charge current to
maintain the die temperature at approximately 115°C.
However, the approximate ambient temperature at which
the thermal feedback begins to protect the IC is:
T
A
= 115°C – P
D
θ
JA
T
A
= 115°C – (V
CC
– V
BAT
) • I
BAT
• θ
JA
Example: Consider an LTC4059 operating from a 5V wall
adapter providing 900mA to a 3.7V Li-Ion battery. The
ambient temperature above which the LTC4059
/LTC4059A
begin to reduce the 900mA charge current is approximately:
T
A
= 115°C – (5V – 3.7V) • (900mA) • 50°C/W
T
A
= 115°C – 1.17W • 50°C/W = 115°C – 59°C
T
A
= 56°C
The LTC4059 can be used above 56°C, but the charge
current will be reduced from 900mA. The approximate
current at a given ambient temperature can be calculated:
ICT
VV
BAT A
CC BAT JA
=°
()
115 –
–•θ
Using the previous example with an ambient temperature
of 65°C, the charge current will be reduced to approximately:
ICC
VV CW
C
CA
ImA
BAT
BAT
=°°
()
°=°
°
=
115 65
537 50
50
65
770
–
–. • / /
Furthermore, the voltage at the PROG pin will change
proportionally with the charge current as discussed in the
Programming Charge Current section.
It is important to remember that LTC4059
/LTC4059A
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 115°C.
Board Layout Considerations
In order to be able to deliver maximum charge current
under all conditions, it is critical that the exposed metal
pad on the backside of the LTC4059
/LTC4059A
package is
soldered to the PC board ground. Correctly soldered to a
2500mm
2
double sided 1oz copper board the LTC4059
/
LTC4059A
have a thermal resistance of approximately
60°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 60°C/W. As an example, a correctly soldered LTC4059
/
LTC4059A
can deliver over 900mA to a battery from a 5V
supply at room temperature. Without a backside thermal
connection, this number could drop to less than 500mA.
Stability Considerations
The LTC4059 contains two control loops: constant voltage
and constant current. The constant-voltage loop is stable
without any compensation when a battery is connected
with low impedance leads. Excessive lead length, how-
ever, may add enough series inductance to require a
bypass capacitor of at least 1µF from BAT to GND. Further-
more, a 4.7µF capacitor with a 0.2Ω to 1Ω series resistor
from BAT to GND is required to keep ripple voltage low
when the battery is disconnected.
High value capacitors with very low ESR (especially ce-
ramic) reduce the constant-voltage loop phase margin.
Ceramic capacitors up to 22µF may be used in parallel with
a battery, but larger ceramics should be decoupled with
0.2Ω to 1Ω of series resistance.
I
n constant-current mode, the PROG pin is in the feedback
loop, not the battery. Because of the additional pole
created by PROG pin capacitance, capacitance on this pin
must be kept to a minimum. With no additional capaci-
tance on the PROG pin, the charger is stable with program
resistor values as high as 12k. However, additional ca-
pacitance on this node reduces the maximum allowed
APPLICATIO S I FOR ATIO
WUUU
LTC4059/LTC4059A
10
4059fb
program resistor. The pole frequency at the PROG pin
should be kept above 500kHz. Therefore, if the PROG pin
is loaded with a capacitance, CPROG, the following equa-
tion should be used to calculate the maximum resistance
value for RPROG:
RC
PROG
PROG
≤
π
1
2510
5
•• •
Average, rather than instantaneous, battery 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
APPLICATIO S I FOR ATIO
WUUU
filter can be used on the PROG pin to measure the average
battery current as shown in Figure 4. A 20k resistor has
been added between the PROG pin and the filter capacitor
to ensure stability.
V
CC
Bypass Capacitor
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. For more information, refer to
Application Note 88.
Figure 4. Isolating Capacitive Load on PROG Pin and Filtering
Figure 5. Photo of Typical Circuit (2.5mm × 2.7mm)
LTC4059
CFILTER
CHARGE CURRENT
MONTIOR CIRCUITRY
RPROG
20k
4059 F04
PROG
GND
LTC4059/LTC4059A
11
4059fb
U
PACKAGE DESCRIPTIO
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703)
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.
2.00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
0.38 ± 0.05
BOTTOM VIEW—EXPOSED PAD
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
R = 0.115
TYP
1.37 ±0.05
(2 SIDES)
1
3
64
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DC6) DFN 1103
0.25 ± 0.05
0.50 BSC
0.25 ± 0.05
1.42 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.61 ±0.05
(2 SIDES)
1.15 ±0.05
0.675 ±0.05
2.50 ±0.05
PACKAGE
OUTLINE
0.50 BSC
PIN 1
CHAMFER OF
EXPOSED PAD
LTC4059/LTC4059A
12
4059fb
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2003
LT/LT 0505 REV B • PRINTED IN USA
PART NUMBER DESCRIPTION COMMENTS
LTC1733 Monolithic Lithium-Ion Linear Battery Charger Standalone Charger with Programmable Timer, Up to 1.5A Charge Current
LTC1734 Lithium-Ion Linear Battery Charger in ThinSOTTM Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed
LTC1998 Lithium-Ion Low Battery Detector 1% Accurate 2.5µA Quiescent Current, SOT-23
LTC4050 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 Monolithic Lithium-Ion Battery Pulse Charger No Blocking Diode or External Power FET Required
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 Thermal Regulation Prevents Overheating, C/10 Termination,
with Integrated Pass Transistor in ThinSOT C/10 Indicator
LTC4056 Standalone Lithium-Ion Linear Battery Charger Standalone Charger with Programmable Timer, No Blocking Diode,
in ThinSOT No Sense Resistor Needed
LTC4057 Monolithic Lithium-Ion Linear Battery Charger No External MOSFET, Sense Resistor or Blocking Diode Required,
with Thermal Regulation in ThinSOT Charge Current Monitor for Gas Gauging
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
LTC4058 950mA Standalone Li-Ion Charger in 3mm × 3mm USB Compatible, Thermal Regulation Protects Against Overheating
DFN
ThinSOT is a trademark of Linear Technology Corporation.
RELATED PARTS
U
TYPICAL APPLICATIO
VCC
LTC4059
VIN
4.5V TO 6.5V
EN
Li CC
BAT
1µF
2k
4.2V
Li-Ion
BATTERY
600mA
4059 TA03
PROG
GND
+
