LTC4050EMS-4.2 [Linear]
Lithium-Ion Linear Battery Charger with Thermistor Interface; 锂离子电池线性充电器，热敏电阻接口
| 型号： | LTC4050EMS-4.2 |
| 厂家： | 
Linear |
| 描述： | Lithium-Ion Linear Battery Charger with Thermistor Interface |
| 文件： | 总12页 (文件大小：185K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4050
Lithium-Ion Linear Battery
Charger with Thermistor Interface
U
FEATURES
DESCRIPTIO
TheLTC®4050-4.1/LTC4050-4.2arecompletestandalone
constant-current/constant-voltage linear charge control-
lers for lithium-ion (Li-Ion) batteries. Charge current is
programmable and final float voltage has ±1% accuracy.
■
Complete Standalone Linear Charger Controller
for 1-Cell Lithium-Ion Batteries
■
Thermistor Interface for Battery Temperature
Sensing
■
Preset Charge Voltage with ±1% Accuracy
Whentheinputsupplyisremoved,theLTC4050automati-
cally enters a low quiescent current sleep mode, dropping
the battery drain current to 5µA. An internal comparator
detects the near-end-of-charge (C/10) condition while a
programmable timer, using an external capacitor, sets the
total charge time. Fully discharged cells are automatically
trickle charged at 10% of the programmed current until
cell voltage exceeds 2.49V. The thermistor interface
suspends charging if the cell temperature is outside of a
0°C to 50°C temperature window.
■
Programmable Charge Current
■
C/10 Charge Current Detection Output
■
Programmable Charge Termination Timer
■
Input Supply (Wall Adapter) Detection Output
■
4.5V to 10V Input Voltage Range
■
Automatic Sleep Mode When Input Supply
is Removed (Only 5µA Battery Drain)
■
Automatic Trickle Charging of Low Voltage Cells
■
Automatic Battery Recharge
Battery Insertion Detection
Space Saving 10-Pin MSOP Package
■
■
TheLTC4050beginsanewchargecyclewhenadischarged
batteryisconnectedtothechargerorwhentheinputpower
is applied. In addition, a new charge cycle is automatically
startedifthebatteryremainsconnectedtothechargerand
the cell voltage drops below 3.88V for 4.1V cells or below
3.98V for 4.2V cells.
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APPLICATIO S
■
Cellular Phones
■
Handheld Computers
■
Charging Docks and Cradles
The LTC4050 is available in the 10-pin MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Charge Current vs
Single Cell 4.2V 500mA Li-Ion Battery Charger
Thermistor Temperature
V
IN
6V
600
V
= 3.7V
BAT
MBRM120T3
500
400
300
8
1k
0.2Ω
V
1µF
CC
1k
9
7
SENSE
DRV
LTC4050-4.2
3
Si9430DY
= 500mA
CHRG
I
BAT
200
100
0
10
4
1
6
ACPR
BAT
TIMER
PROG
*
4.2V
Li-Ion
CELL
GND NTC
+
10k NTC
0.1µF
10µF
19.6k
T
DALE NTHS-1206N02
5
2
50
100 125
–50 –25
0
25
75
THERMISTOR TEMPERATURE (°C)
4050 TA01
4050 TA05
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
4050f
1
LTC4050
W W
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
Input Supply Voltage (VCC) ...................................... 12V
SENSE, DRV, BAT, SEL,
TIMER, PROG, CHRG, ACPR .................–0.3V to 12V
Operating Temperature Range (Note 2) . –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
TOP VIEW
LTC4050EMS-4.1
LTC4050EMS-4.2
BAT
NTC
CHRG
TIMER
GND
1
2
3
4
5
10 ACPR
9
8
7
6
SENSE
V
CC
DRV
PROG
MS PACKAGE
10-LEAD PLASTIC MSOP
MS PART MARKING
TJMAX = 140°C, θJA = 180°C/W
LTTW
LTTX
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. V = 6V unless otherwise noted.
A
CC
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Supply Voltage
Input Supply Current
●
4.5
10
V
CC
I
CC
Charger On, Current Mode
Shutdown Mode
Sleep Mode (Battery Drain Current)
●
●
1.3
1.3
5
3
3
15
mA
mA
µA
V
BAT
Regulated Output (Float) Voltage in
Constant Voltage Mode
LTC4050-4.1; 5V ≤ V ≤ 10V, 0°C ≤ T ≤ 85°C
4.059
4.158
4.039
4.137
4.1
4.2
4.1
4.2
4.141
4.242
4.141
4.242
V
V
V
V
CC
A
LTC4050-4.2; 5V ≤ V ≤ 10V, 0°C ≤ T ≤ 85°C
CC
A
LTC4050-4.1; 5V ≤ V ≤ 10V
●
●
CC
LTC4050-4.2; 5V ≤ V ≤ 10V
CC
I
I
Current Mode Charge Current
R
R
R
= 19.6k, R
= 19.6k, R
= 97.6k, R
= 0.2Ω
= 0.2Ω
= 0.2Ω
440
415
60
500
535
585
140
mA
mA
mA
BAT
PROG
PROG
PROG
SENSE
SENSE
SENSE
●
100
55
Trickle Charge Current
V
= 2V, R
= 19.6k, I
= (V – V )/0.2Ω
SENSE
●
●
●
20
90
2.58
4.5
mA
V
TRIKL
BAT
PROG
TRIKL
CC
V
V
Trickle Charge Threshold Voltage
2.41
2.49
4
TRIKL
V
CC
V
CC
Undervoltage Lockout Voltage
Undervoltage Lockout Hysteresis
V
UV
∆V
130
3.6
mV
V
UV
V
PROG Pin Manual Shutdown
Threshold Voltage
MSD
V
ASD
Automatic Shutdown Threshold Voltage
(V – V ) High to Low
25
40
54
69
85
100
mV
mV
CC
BAT
(V – V ) Low to High
CC
BAT
I
PROG Pin Current
Internal Pull-Up Current, No R
2.3
µA
µA
PROG
PROG
PROG Pin Source Current, ∆V
≤ 5mV
●
300
PROG
V
V
PROG Pin Voltage
R
=19.6k
PROG
2.47
0.525
32
V
V
PROG
ACPR
CHRG
ACPR Pin Output Low Voltage
CHRG Pin Weak Pull-Down Current
CHRG Pin Output Low Voltage
Thermistor Resistance for Hot Fault
Thermistor Resistance for Cold Fault
I
= 5mA
ACPR
I
V
= 1V
µA
V
CHRG
CHRG
V
CHRG
I
= 5mA
0.525
4.1
R
R
3.7
25
4.4
31
kΩ
kΩ
HOT
28.5
COLD
4050f
2
LTC4050
ELECTRICAL CHARACTERISTICS
The
● denotes the specifications which apply over the full operating
CC
temperature range, otherwise specifications are at T = 25°C. V = 6V unless otherwise noted.
A
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
50
MAX
UNITS
mA
%
I
t
10% Charge Current Indication Level
TIMER Accuracy
R
= 19.6k, R = 0.2Ω
SENSE
●
25
100
C/10
PROG
C
V
V
= 0.1µF
10
TIMER
TIMER
VRECHRG
Recharge Threshold Voltage
from High to Low (LTC4050-4.1)
from High to Low (LTC4050-4.2)
3.83
3.93
3.88
3.98
V
BAT
BAT
V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC4050E is 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.
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TYPICAL PERFOR A CE CHARACTERISTICS
Trickle Charge Current
vs Temperature
Charge Current vs Temperature
Charge Current vs V
CC
70
65
60
55
520
515
510
505
500
495
490
485
480
540
520
500
480
R
R
V
= 19.6k
R
R
V
= 19.6k
PROG
SEN
BAT
PROG
SEN
BAT
R
R
= 19.6k
PROG
SEN
BAT
= 0.2Ω
= 0.2Ω
= 0.2Ω
= 2V
= 6V
= 3V
= 25°C
V
V
= 3V
= 6V
V
T
CC
A
CC
50
45
40
460
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
8
10
4
6
–50 –25
0
25
50
75 100 125
TEMPERATURE (°C)
V
(V)
CC
LTC4050 G03
LC4050 G02
LTC4050 G01
Trickle Charge Threshold Voltage
vs Temperature
Trickle Charge Threshold Voltage
Trickle Charge Current vs V
vs V
CC
CC
2.51
2.50
2.49
2.48
2.47
2.46
2.55
2.54
70
65
R
A
= 19.6k
PROG
= 25°C
R
R
= 19.6k
V
= 6V
PROG
PROG
SEN
BAT
CC
T
= 0.2Ω
R
= 19.6k
V
= 2V
= 25°C
2.53
2.52
2.51
T
A
60
55
2.50
2.49
50
45
40
2.48
2.47
2.46
2.45
–50 –25
0
25
50
75 100 125
4
6
8
10
4
8
10
6
TEMPERATURE (°C)
V
(V)
V
CC
(V)
CC
LTC4050 G05
LTC4050 G04
LTC4050 G06
3
LTC4050
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TYPICAL PERFOR A CE CHARACTERISTICS
Recharge Threshold Voltage
vs Temperature
PROG Pin Voltage vs Temperature
PROG Pin Voltage vs V
CC
2.480
2.475
2.470
2.465
2.50
2.49
2.48
2.47
2.46
2.45
4.1
4.0
3.9
3.8
V
= 6V
PROG
R
= 19.6k
V
CC
= 6V
CC
PROG
T = 25°C
A
R
= 19.6k
LTC4050-4.2
LTC4050-4.1
2.460
2.455
2.450
3.7
50
0
TEMPERATURE (°C)
100 125
6
8
10
–50 –25
25
75
4
–50 –25
0
25
50
75 100 125
TEMPERATURE (°C)
V
CC
(V)
LTC4050 G08
LTC4050 G09
LTC4050 G07
NTC R
Threshold Voltage
HOT
Timer Accuracy vs Temperature
Timer Accuracy vs V
vs Temperature
CC
4.16
110
105
100
95
110
105
100
95
V
CC
= 6V
V
C
T
= 3V
V
V
C
= 6V
= 3V
TIMER
BAT
TIMER
A
CC
BAT
= 0.1µF
= 25°C
= 0.1µF
4.14
4.12
4.10
4.08
4.06
4.04
90
90
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
50
75 100 125
–50 –25
0
25
75
4
5
6
7
8
9
10
TEMPERATURE (°C)
V
(V)
CC
LTC4050 G10
LTC4050 G12
LTC4050 G11
NTC R
Threshold Voltage
NTC R
Threshold Voltage
NTC R
Threshold Voltage
HOT
COLD
COLD
vs V
vs V
vs Temperature
CC
CC
4.150
4.125
4.100
4.075
4.050
28.60
29.0
28.9
28.8
28.7
28.6
28.5
28.4
28.3
28.2
V
CC
= 6V
T
= 25°C
T
= 25°C
A
A
28.55
28.50
28.45
28.40
28.1
8
8
4
10
4
10
6
6
–50 –25
0
25
125
50
75 100
TEMPERATURE (°C)
V
CC
(V)
V
CC
(V)
LT4050 G14
LTC4050 G15
LTC4050 G13
4
LTC4050
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PIN FUNCTIONS
BAT (Pin 1): Battery Sense Input. A precision internal
resistor divider on this pin sets the final float voltage. The
resistor divider is disconnected in sleep mode to reduce
the current drain on the battery. A bypass capacitor of
10µF or more is required to keep the loop stable when the
battery is not connected.
PROG (Pin 6): Charge Current Program and Shutdown
Input Pin. The charge current is programmed by connect-
ing a resistor, RPROG to ground. The charge current is IBAT
= (VPROG • 800Ω)/(RPROG • RSENSE). The IC can be forced
into shutdown by floating the PROG pin and allowing the
internal2.3µAcurrentsourcetopullthepinabovethe3.6V
shutdown threshold voltage.
NTC (Pin 2): Thermistor Interface Input. A 10kΩ Dale
Curve 2 NTC thermistor (or other 10kΩ NTC thermistor
with a room temperature beta of around 3400) is con-
nected from this pin to ground. The charge cycle will be
disabled and the timer will be placed on hold if the
thermistor temperature is above 50°C or below 0°C.
DRV (Pin 7): Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. The impedance is high at this pin,
therefore, if a PNP pass transistor is used, it must have
high gain.
VCC (Pin 8): Positive Input Supply Voltage. VCC can range
from 4.5V to 10V. Bypass this pin with a 1µF capacitor.
When VBAT is within 54mV of VCC, the LTC4050 is forced
into sleep mode, dropping ICC to 5µA.
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 current
dropsto10%ofthefull-scalecurrentformorethan15ms,
the N-channel MOSFET turns off and a 32µA current
source is connected from the CHRG pin to GND. When the
timer runs out or the input supply is removed, the current
source is disconnected and the CHRG pin becomes high
impedance.
SENSE (Pin 9): Current Sense Input. A sense resistor,
RSENSE, must be connected from VCC to the SENSE pin.
Select a resistor value that will develop approximately
100mV at the programmed full-scale charge current.
This resistor is chosen using the following equation:
RSENSE = (VPROG • 800Ω)/(RPROG • IBAT
)
TIMER (Pin 4): Timer Capacitor and Constant-Voltage
ACPR (Pin 10): Wall Adapter Present Output. When the
inputvoltage(walladaptor)isappliedtotheLTC4050, this
pin is pulled to ground by an internal N-channel MOSFET
that is capable of sinking 5mA suitable for driving an
external LED.
Mode Disable Input Pin. The timer period is set by placing
a capacitor, CTIMER, to GND. The timer period is tTIMER
=
(CTIMER • 3 hours)/(0.1µF). Shorting the TIMER pin to
GND will disable the internal timer function and the C/10
function.
GND (Pin 5): Ground.
4050f
5
LTC4050
W
BLOCK DIAGRA
V
CC
8
UV
–
3.88V (LTC4050-4.1)
3.98V (LTC4050-4.2)
+
–
+
C5
28.6k
NTC
–
R
SENSE
2
SENSE
+
–
9
+
C1
+
–
54mV
80Ω
800Ω
+
–
CHRG
3
C4
–
+
C/10 STOP RECHRG C/10
720Ω
DRV
BAT
32µA
CA
7
1
ACPR
SHDN
LOGIC
–
+
SLP
C2
VA
LBO
TIMER
4
OSCILLATOR
COUNTER
3.6V
V
REF
–
+
ACPR
10
+
–
+
–
C3
A1
V
CC
V
REF
2.47V
2.3µA
CHARGE
PROG
GND
6
5
4050 BD
BATTERY CURRENT I
BAT
= (2.47V • 800Ω)/(R
• R
)
SENSE
PROG
R
PROG
4050f
6
LTC4050
U
OPERATIO
The LTC4050 is a linear battery charger controller. The
charge current is programmed by the combination of a
program resistor (RPROG) from the PROG pin to ground
and a sense resistor (RSENSE) between the VCC and SENSE
pins. RPROG sets a program current through an internal
trimmed 800Ω resistor setting up a voltage drop from VCC
to the input of the current amplifier (CA). The current
amplifierservosthegateoftheexternalP-channelMOSFET
to force the same voltage drop across RSENSE which sets
the charge current. When the voltage at the BAT pin
approaches the preset float voltage, the voltage amplifier
(VA) will start sinking current which reduces the voltage
drop across RSENSE, thus reducing the charge current.
at the CHRG pin and connect a weak current source to
ground, indicating that the battery is nearly fully charged
(C/10 occurs at approximately 94% charge).
An external capacitor on the TIMER pin sets the total
charge time. After a time-out occurs, the charge cycle is
terminatedandtheCHRGpinisforcedhighimpedance.To
restart the charge cycle, remove the input voltage and
reapply it, or momentarily float the PROG pin.
Replacing the battery when charging will cause the timer
to be reset if the cell voltage of the new battery is below
3.88V (for 4.1V cells) or 3.98V (for 4.2V cells). If the
voltage is above 3.88V(for 4.1V cells) or 3.98V (for 4.2V
cells) the timer will continue for the remaining charge
time. In the case when a time out has occurred, a new
battery with a cell voltage of less than 3.88V or 3.98V can
be inserted and charged automatically with the full pro-
grammed charge time.
A charge cycle begins when the voltage at VCC pin rises
above the UVLO level, a program resistor is connected
from the PROG pin to ground, and the NTC thermistor
temperature is between 0°C and 50°C. At the beginning of
the charge cycle, if the battery voltage is below 2.49V, the
charger goes into trickle charge mode. The trickle charge
current is 10% of the full-scale current. If the cell voltage
stays low for one quarter of the total charge time, the
charge sequence will terminate.
For batteries like lithium-ion that require accurate final
float voltage, the internal 2.47V reference, voltage ampli-
fier and the resistor divider provide regulation with ±1%
(max) accuracy.
The charger can be shut down by floating the PROG pin.
An internal current source will pull it high and clamp at
3.5V.
The charger goes into the fast charge constant-current
mode after the voltage on the BAT pin rises above 2.49V.
In constant-current mode, the charge current is set by the
combination of RSENSE and RPROG
.
When the input voltage is not present, the charger goes
into a sleep mode, dropping ICC to 5µA. This greatly
reduces the current drain on the battery and increases the
standby time.
When the battery approaches the final float voltage, the
charge current will begin to decrease. When the current
drops to 10% of the full-scale charge current, an internal
comparatorwillturnoffthepull-downN-channelMOSFET
4050f
7
LTC4050
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APPLICATIONS INFORMATION
Charger Conditions
Programming Charge Current
Thechargerisoffwhenanyofthefollowingconditionsexist:
thevoltageattheVCC pinisbelow4V,thevoltageattheVCC
The formula for the battery charge current (see Block
Diagram) is:
pin is greater than 4V but is less than 54mV above VBAT
,
IBAT = (IPROG)(800Ω/RSENSE
)
the PROG pin is floating, the timer has timed out or the
thermistortemperatureisoutsidetheacceptablerange. In
thiscondition, theDRVpinispulledtoVCC andtheinternal
resistordividerisdisconnectedtoreducethecurrentdrain
on the battery.
= (2.47V/RPROG)(800Ω/RSENSE) or
RPROG = (2.47V/IBAT)(800Ω/RSENSE
)
where RPROG is the total resistance from the PROG pin to
ground.
For example, if 0.5A charge current is needed, select a
value for RSENSE that will drop 100mV at the maximum
chargecurrent.RSENSE =0.1V/0.5A=0.2Ω,thencalculate:
Undervoltage Lockout (UVLO)
Aninternalundervoltagelockoutcircuitmonitorstheinput
voltageandkeepsthechargerinshutdownmodeuntilVCC
rises above the undervoltage lockout threshold of 4V. To
prevent oscillation around VCC = 4V, the UVLO circuit has
built-in hysteresis.
RPROG = (2.47V/500mA)(800Ω/0.2Ω) = 19.76k
For best stability over temperature and time, 1% resistors
are recommended. The closest 1% resistor value is 19.6k.
Trickle Charge and Defective Battery Detection
Programming the Timer
At the beginning of the charging sequence, if the battery
voltage is low (below 2.49V), the charger goes into trickle
mode. In this mode, the charge current is reduced to 10%
of the full-scale current. If the low cell voltage persists for
one quarter of the total charge time, the battery is consid-
ered defective, the charge cycle is terminated and the
CHRG pin output becomes high impedance.
The programmable timer terminates the charge cycle.
Typically when charging at a 1C rate, a discharged Li-Ion
battery will become fully charged in 3 hours. For lower
charge current rates, extend the time accordingly. The
length of the timer is programmed by an external capaci-
tor at the TIMER pin. The total charge time is:
Time (Hours) = (3 Hours) • (CTIMER/0.1µF) or
CTIMER = 0.1µF • Time (Hours)/3 Hours
Shutdown
The LTC4050 can be forced into shutdown by floating the
PROG pin and allowing the internal 2.3µA current source
to pull the pin above the 3.6V shutdown threshold voltage.
In shutdown, the DRV pin is pulled up to VCC, turning off
the external P-channel MOSFET and resetting the internal
timer.
The timer starts when an input voltage greater than 4V is
applied and the program resistor is connected to ground.
After a time-out occurs, the CHRG output will go high
impedance to indicate that charging has stopped. To dis-
able the timer function, short the TIMER pin to GND.
+
V
V
DD
8
V
CC
400k
µPROCESSOR
LTC4050
CHRG
2k
3
OUT
IN
4050 F01
Figure 1. Microprocessor Interface
4050f
8
LTC4050
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APPLICATIONS INFORMATION
CHRG Status Output Pin (C/10)
N-channel MOSFET that is capable of driving an LED.
Otherwise, this pin is in a high impedance state.
When the charge cycle starts, the CHRG pin is pulled to
groundbyaninternalN-channelMOSFETthatcandrivean
LED. When the charge current drops to 10% of the full-
scale current (C/10), the N-channel MOSFET turns off and
a weak 32µA current source to ground is connected to the
CHRG pin. After a time-out occurs, the pin goes high
impedance. By using two different value pull-up resistors,
a microprocessor can detect three states from this pin
(charging, C/10 and stop charging). See Figure 1.
Gate Drive
Typically the LTC4050 controls an external P-channel
MOSFET to supply current to the battery. An external PNP
transistor can also be used as the pass transistor instead
of the P-channel MOSFET. Due to the low current gain of
the current amplifier (CA), a high gain Darlington PNP
transistor is recommended to avoid excessive charge
current error. The gain of the current amplifier is around
0.6µA/mV. For every 1µA of base current, a 1.6mV of gain
error shows up at the inputs of CA. With RPROG = 19.6k
(100mV across RSENSE), it represents 1.67% of error in
charge current.
When the LTC4050 is in charge mode, the CHRG pin is
pulled low by an internal N-channel MOSFET. To detect
this mode, force the digital output pin, OUT, high and
measure the voltage at the CHRG pin. The N-channel
MOSFET will pull the pin low even with a 2k pull-up
resistor. Once the charge current drops to 10% of the full-
scale current (C/10), the N-channel MOSFET turns off and
a 32µA current source is connected to the CHRG pin. The
IN pin will then be pulled high by the 2k pull-up. By forcing
the OUT pin into a high impedance state, the current
source will pull the pin low through the 400k resistor.
When the internal timer has expired, the CHRG pin will
change to high impedance state and the 400k resistor will
then pull the pin high to indicate charging has stopped.
Battery Detection
The LTC4050 can detect the insertion of a new battery.
When a battery with a voltage of less than 3.88V (for 4.1V
cells) or 3.98V (for 4.2V cells) is inserted, the LTC4050
resets the timer and starts a new charge cycle. If the cell
voltage of the new battery is above 3.88V (for 4.1V cells)
or3.98V(for4.2Vcells), anewchargecyclewillnotbegin.
If a new battery (with cell voltage above 3.88V) is inserted
while in the charging process, the timer will not be reset,
but will continue until the timer runs out.
The CHRG pin open-drain device will turn on if the BAT pin
falls below the trickle charge threshold and the LTC4050
has neither timed out nor been put into shutdown. For
example, if the battery and NTC thermistor are both
disconnected from the typical application circuit, the BAT
voltagewillcollapseduetothethermalfaultandCHRGwill
pull low. Entering shutdown by floating the PROG pin will
prevent the CHRG pulldown from turning on.
After a time out has occurred and the battery remains
connected, a new charge cycle will begin if the battery
voltage drops below the recharge threshold of 3.88V (for
4.1V cells) or 3.98V (for 4.2V cells) due to self-discharge
or external loading.
Stability
ACPR Output Pin
The charger is stable without any compensation when a
P-channel MOSFET is used as the pass transistor.
However, a 10µF capacitor is recommended at the BAT
pin to keep the ripple voltage low when the battery is
disconnected.
The LTC4050 has an ACPR output pin to indicate that the
input supply (wall adapter) is higher than 4V and 54mV or
more above the voltage at the BAT pin. When both condi-
tions are met, the ACPR pin is pulled to ground by an
4050f
9
LTC4050
U
W U U
APPLICATIONS INFORMATION
If a PNP transistor is chosen as the pass transistor, a
1000pFcapacitorisrequiredfromtheDRVpintoVCC. This
capacitor is needed to help stabilize the voltage loop. A
10µF capacitor at the BAT pin is also recommended when
a battery is not present.
28.6k trimmed thin film resistor that connects to VCC
through a P-channel MOSFET. This MOSFET also biases
an internal resistor string to ground, from which voltage
thresholds of approximately VCC/2 and VCC/8 are derived.
The NTC pin is compared to these thresholds by two
comparators that have wired-OR outputs. The thresholds
are selected such that an overtemperature condition will
occur when the thermistor resistance is less than approxi-
mately 4.1k and undertemperature condition will occur
when the thermistor resistance is greater than approxi-
mately 28.5k. These correspond to thermistor tempera-
tures of 50°C and 0°C for the specific type of thermistor
listed above (many others will be close enough for most
purposes). The MOSFET is turned off during undervoltage
conditions, preventing the dividers that are biased from it
from drawing current from the battery when input power
is removed. The drop across the MOSFET is common to
both resistor dividers and does not cause any loss of
accuracy in the circuit. The comparators have approxi-
mately 10mV of hysteresis to prevent oscillations around
the trip points.
VCC 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 hot power source. These transients can be minimized
byusingX5Rdielectriccapacitorsand/orbyaddinga1.5Ω
resistor in series with the ceramic input capacitor. For
more information, refer to Application Note 88.
Thermistor Interface
A thermistor connected to the NTC (negative temperature
coefficient) pin can be used to sense the battery tempera-
ture to determine if the battery is within an acceptable
temperature range for charging (between 0°C and 50°C).
A Dale (curve 2) 10k thermistor is recommended although
many other types of thermistors can also be used. For
example, aBetaCHIP(curve7)10kthermistororother10k
thermistors with a room temperature beta of approxi-
mately 3400 will work well. The thermistor is connected
from NTC (pin 2) to ground and is biased up by an internal
When an undertemperature or overtemperature condition
is sensed, the current amplifier pulldown is disabled and
DRV is pulled high, the timer is placed in a hold condition
with the count frozen until the battery temperature is
within an acceptable range. The end-of-charge compara-
tor is also disabled to prevent a premature end of charge
signal due to the lack of battery charging current.
NTC Interface Circuitry
V
CC
UV
–
+
28.6k
TBAD
(TO CA,
EOC, TIMER)
NTC
–
+
2
10k DALE
CURVE 2
NTC
THERMISTOR
4050 AI
4050f
10
LTC4050
U
PACKAGE DESCRIPTIO
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.2 – 3.45
(.126 – .136)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.497 ± 0.076
(.0196 ± .003)
REF
0.50
0.305 ± 0.038
(.0120 ± .0015)
TYP
(.0197)
10 9
8
7 6
BSC
RECOMMENDED SOLDER PAD LAYOUT
3.00 ± 0.102
(.118 ± .004)
NOTE 4
4.90 ± 0.15
(1.93 ± .006)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
GAUGE PLANE
1
2
3
4 5
0.53 ± 0.01
(.021 ± .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.13 ± 0.076
(.005 ± .003)
MSOP (MS) 0802
0.50
(.0197)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
4050f
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.
11
LTC4050
U
TYPICAL APPLICATIO S
Linear Charger Using a PNP Transistor
V
IN
6V
MBRM120T3
1k
10k
0.2Ω
1nF
1µF
1k
8
V
CC
ZTX749
9
7
3
CHRG SENSE
10
DRV
2N5087
ACPR
I
= 500mA
BAT
LTC4050-4.2
4
1
6
TIMER
BAT
PROG
0.1µF
4.2V
Li-Ion
CELL
NTC
2
GND
5
19.6k
+
10k NTC
DALE NTHS-1206N02
10µF
T
4050 TA02
Single Cell 4.1V, 1.5A High Efficiency Li-Ion Battery Charger
V
IN
6V
MBRS130LT3
+
0.47µF
4.7Ω
1k
1k
22µF
0.082Ω
8
1/4W
V
CC
SENSE
9
7
3
CHRG
ACPR
8
10
3
T
1
DRV
Si2305DS
7
LTC1693-5
MBRS130LT3
LTC4050-4.1
4
4
1
6
TIMER
BAT
PROG
15µH
0.1µF
CDRH6D28-150NC
NTC GND
19.6k
2
5
4.1V
Li-Ion
CELL
+
+
220µF
10k NTC
DALE
NTHS-1206N02
4050 TA04
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LT®1510-5
LT1512
500kHz Constant-Voltage/Constant-Current Battery Charger Most Compact, Up to 1.5A, Charges NiCd, NiMH, Li-Ion Cells
SEPIC Battery Charger
V Can Be Higher or Lower Than Battery Voltage, 1.5A Switch
IN
LT1620
Rail-to-Rail Current Sense Amplifier
Termination Controller for Li-Ion
Precise Output Current Programming, Up to 32V V , Up to 10A I
OUT
OUT
LTC1729
Time or Charge Current Termination, Automatic Charger/Battery
Detection, Status Output, Preconditioning, 8-Lead MSOP;
Timer; AC Adapter Present Detection; No Firmware Required
LTC1731
Li-Ion Linear Battery Charger Controller
Firmware Required
CC/CV Charges Li-Ion Cells, 8-Lead MSOP, Programmable Timer; No
LTC1732
LTC1733
LTC1734
LTC1734L
Li-Ion Linear Battery Charger Controller
Adapter Present Detection; Programmable Timer; No Firmware Required
Complete Standalone Charger, Thermal Regulator Prevents Overheating
Li-Ion Linear Charger with Thermal Regulation
ThinSOT Li-Ion Linear Battery Charger Controller
Only Two External Components; No Diode; No Sense Resistor; V
PROG
Allows Monitoring I
CHARGE
for Safety; No MOSFET; No Diode; No
CHARGE
LTC4052
Li-Ion Linear Battery Pulse Charger
Detects Maximum I
Firmware Required
LTC4053
USB Compatible Li-Ion Battery Charger
USB and Wall Adapter Input, 100mA/500mA or Up to 1.25A Charge
Current Standalone Charger
ThinSOT is a trademark of Linear Technology Corporation.
4050f
LT/TP 0203 2K • PRINTED IN THE USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
LINEAR TECHNOLOGY CORPORATION 2002
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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