LTC1730ES8-4.2#TR [Linear]
LTC1730 - Lithium-Ion Battery Pulse Chargers with Overcurrent Protection; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C;型号: | LTC1730ES8-4.2#TR |
厂家: | Linear |
描述: | LTC1730 - Lithium-Ion Battery Pulse Chargers with Overcurrent Protection; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C 电源电路 电池 电源管理电路 脉冲 光电二极管 过电流保护 |
文件: | 总12页 (文件大小:159K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC1730-4/LTC1730-4.2
Lithium-Ion Battery
Pulse Charger with
Overcurrent Protection
U
DESCRIPTIO
FEATURES
The LTC®1730 is a complete pulse charger for 1-cell
lithium-ion batteries. When charging a depleted cell, the
internal MOSFET is fully on allowing the current limited
input power source to provide charge current to the
battery,virtuallyeliminatingheatgenerationinthecharger.
■
Complete Pulse Charger for 1-Cell Lithium-Ion
Batteries
■
Sense Resistor Limits Maximum Current for Safety
■
1% Float Voltage Accuracy
■
End-of-Charge (C/10) Detection Output
■
Programmable Charge Termination Timer
As the battery accepts charge and approaches the pro-
grammed voltage, the internal MOSFET begins switching
off and on with the duty cycle gradually decreasing as the
battery approaches a fully charged condition. A program-
mable timer ends the charge cycle. The end-of-charge
condition is indicated at the CHRG pin when the average
charge current falls to C/10. Removing the input voltage
puts the LTC1730 into a sleep mode, dropping the battery
current drain to less than 1µA (maximum).
■
Internal 0.35Ω NMOS Switch
No Blocking Diode Required
■
■
SEL Pin to Set Either 4.1V or 4.2V/Cell (LTC1730-4)
■
Low-Battery Drain (1µA Max) when Input Supply Is
Removed
■
Battery Temperature Sensing and Charge
Qualification
■
Automatic Trickle Charge for Low-Battery
■
Automatic Battery Refresh
An external sense resistor limits the maximum charge
current as a safety precaution against a user connecting a
wall adapter with the incorrect or no current limit. The
internal MOSFET prevents reverse battery current from
flowing if the input voltage is shorted to ground, eliminat-
ing the need for a blocking diode.
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APPLICATIO S
■
Standalone Lithium-Ion Battery Charger
Handheld Computers
Cellular Telephones
■
■
The LTC1730-4 is available in the 16-pin SSOP package
and the LTC1730-4.2 is available in the 8-pin SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
1A, Single Cell 4.2V Li-Ion Battery Charger (8-Pin Package)
V
= 4.5V TO 12V
IN
WITH 1A CURRENT LIMIT
2
R2
10k
4.7Ω
R1
1k
V
IN
R
SENSE
0.05Ω
C1
1µF
C3
0.047µF
R3
4.1k
LTC1730ES8-4.2
D3
7
CHARGE STATUS
GATE
3
6
0.022µF
CHRG
1
8
SENSE
NTC/SHDN
BAT
1-CELL
Li-Ion
BATTERY
R4
10k
NTC*
T
TIMER
5
GND
4
C
TIMER
0.1µF
*NTC: DALE NTHS-1206N02
1730 TA01
1730f
1
LTC1730-4/LTC1730-4.2
W W U W
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltage (VCC) ............................................ 13.2V
SENSE, GATE, BAT,
TIMER, NTC/SHDN, SEL ............................ –0.3V to VCC
CHRG, ACPR, FAULT ..............................–0.3V to 13.2V
Operating Junction
Temperature Range (Note 2) .................. –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
TOP VIEW
ORDER PART
ORDER PART
1
2
3
4
5
6
7
8
GND*
BAT
16
15
14
13
12
11
10
9
GND*
NUMBER
NUMBER
SENSE
ACPRB
1
2
3
4
8
7
6
5
BAT
SENSE
GATE
CHRG
TIMER
LTC1730EGN-4
LTC1730ES8-4.2
NC**
V
CC
V
IN
GATE
ACPR
FAULT
CHRG
NC**
GND
SEL
S8 PACKAGE
8-LEAD PLASTIC SO
NTC/SHDN
TIMER
GND*
GN PART MARKING
17304
TJMAX = 125°C, θJA = 110°C/W
S8 PART MARKING
173042
GND*
GN PACKAGE
16-LEAD PLASTIC SSOP
*
FOUR CORNER PINS ARE FUSED TO
INTERNAL DIE ATTACH PADDLE FOR
HEAT SINKING. CONNECT THESE FOUR
PINS TO EXPANDED PC LANDS FOR
PROPER HEAT SINKING.
** NO INTERNAL CONNECTION
TJMAX = 125°C, θJA = 90°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted.
SYMBOL
PARAMETER
Supply Voltage
Supply Current
CONDITIONS
MIN
TYP
MAX
UNITS
V
●
4.5
12
V
CC
I
Charger On; Fast Charge Mode
●
●
●
2
2
5
5
1
mA
mA
µA
CC
Shutdown: V
= 0V
= 4V
NTC/SHDN
Sleep Mode; V
BAT
V
Regulated Output Voltage
LTC1730ES8-4.2 (5V ≤ V ≤ 12V)
●
●
●
4.158
4.059
4.158
4.2
4.1
4.2
4.242
4.141
4.242
V
V
V
BAT
CC
LTC1730EGN-4 (5V ≤ V ≤ 12V), SEL = GND
CC
LTC1730EGN-4 (5V ≤ V ≤ 12V), SEL = V
CC
CC
I
I
Maximum Charge Overcurrent
Trickle Charge Current
R
= 0.1Ω
●
0.7
15
1
1.3
60
A
mA
V
MAX
SENSE
V
= 2V
BAT
35
TRICKL
V
V
Trickle Charge Trip Threshold
2.45
2.55
150
TRICKL
ASD
Automatic Shutdown Threshold Voltage
(Sleep Mode)
(V – V ) Low to High
(V – V ) High to Low
mV
mV
CC
BAT
0
CC
BAT
R
Internal Switch On-Resistance
Shutdown Threshold Voltage
V
= 4V
0.35
Ω
DS(ON)
BAT
V
NTC/SHDN Pin High to Low
50
mV
SHDN
1730f
2
LTC1730-4/LTC1730-4.2
DC ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
70
UNITS
µA
I
CHRG Pin Pull-Down Current
TIMER Accuracy
V
C
= 1V, C/10 Mode
10
40
CHRG
CHRG
T
= 0.1µF
10
%
TIMER
TIMER
V
GATE Pin Voltage
V
V
= 3V
= 4V
7.5
10
V
V
GATE
BAT
BAT
T
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
140
5
°C
°C
SHDN
∆T
SHDN
∆V
Recharge Battery Voltage Offset from
Full Charged Battery Voltage
V
– V (Note 3)
RECHRG
150
mV
RECHRG
NTC_HOT
NTC_COLD
BAT(Full Charged)
V
V
NTC/SHDN Pin Threshold Voltage (Hot)
High to Low; V = 4V
Hysteresis
●
●
1.95
3.4
2
50
2.05
3.6
V
mV
CC
NTC/SHDN Pin Threshold Voltage (Cold)
Low to High; V = 4V
Hysteresis
3.5
45
V
mV
CC
V
V
V
V
SEL Pin Threshold
LTC173ECGN-4
0.7
V
V
V
V
SEL
ACPR Pin Output Low Voltage
FAULT Pin Output Low Voltage
CHRG Pin Output Low Voltage
LTC1730EGN-4, I
LTC1730EGN-4, I
= 5mA
0.6
1.2
0.9
ACPR
FAULT
CHRG
ACPR
= 3mA
FAULT
I
= 5mA, Charging Mode
CHRG
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 2: The LTC1730-4/LTC1730-4.2 are guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
Note 3: For the LTC1730-4 version, the full charged V
typically 4.1V.
value is
BAT
1730f
3
LTC1730-4/LTC1730-4.2
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TYPICAL PERFOR A CE CHARACTERISTICS
Trickle Charge Current vs Input
Supply Voltage
Trickle Charge Threshold Voltage
vs Temperature
Trickle Charge Current vs
Temperature
50
45
40
35
30
25
20
50
45
40
35
30
25
20
2.50
2.48
2.46
2.44
2.42
2.40
T
= 25°C
V
= 6V
A
V
= 6V
CC
CC
9
11
12
–50 –25
0
25
50
75 100 125
5
6
7
8
10
50
TEMPERATURE (°C)
–50 –25
0
25
75 100 125
V
(V)
TEMPERATURE (°C)
CC
1730 G01
1730 G03
1730 G02
Internal Switch On-Resistance vs
Temperature
Timer Accuracy vs Temperature
Overcurrent vs Temperature
115
110
105
100
95
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.50
0.45
0.40
0.35
0.30
0.25
0.20
V
= 6V
SEN
V
BAT
= 4V
V
C
= 6V
CC
CC
TIMER
R
= 0.1Ω
= 0.1µF
90
85
80
50
50
50
–50 –25
0
25
75 100 125
–50 –25
0
25
75 100 125
–50 –25
0
25
75 100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
1730 G06
1730 G07
1730 G05
Battery Recharge Threshold Offset
from VBAT vs Temperature
CHRG Pin Output Low Voltage vs
Temperature
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
300
250
200
150
100
50
V
= 6V
CC
0
50
TEMPERATURE (°C)
–50 –25
0
25
75 100 125
50
TEMPERATURE (°C)
–50 –25
0
25
75 100 125 150
1730 G08
1730 G09
1730f
4
LTC1730-4/LTC1730-4.2
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LTC1730ES8-4.2
above 0.875 • VCC, or 3.5V at cold (with VCC = 4V), the
charge cycle is suspended and the internal timer is frozen.
The CHRG pin output status is not affected in this hold
state.
SENSE (Pin 1): Maximum Overcurrent Sense Input. A
sense resistor (RSENSE) should be connected from VCC to
the SENSE pin. When the voltage drop across RSENSE
exceeds 100mV, the pass transistor immediately turns off
and turns back on after a 400ms time-out period (CTIMER
= 0.1µF). The on-off cycle will continue, as long as the
overcurrent condition persists or until the timer runs out.
If overcurrent protection is not needed, short SENSE to
VCC.
When this pin is pulled below 50mV, the IC goes into the
shutdown mode. The charging stops (the GATE pin is
pulled to ground) the timer is reset and the CHRG pin goes
into a high impedance state.
GATE (Pin 7): Gate Drive Output Pin for Internal and
ExternalPassTransistors. AnexternalN-MOSFETtransis-
tor can be connected in parallel with the internal transistor
to reduce the on-resistance for higher charge current. In
this case, an external blocking diode is required to prevent
damage to the battery if VCC is shorted to ground. A 10µA
current source pulls this pin up to the charge pump
potential when turned on and a 40µA current source pulls
it down to ground to turn it off. If an overcurrent condition
is detected, the GATE pin is immediately pulled to ground.
V
CC (Pin 2): Positive Input Supply Voltage (4.5V ≤ VCC ≤
13.2V). Bypass this pin with a 1µF capacitor in series with
a 4.7Ω resistor. An RC network from the VCC pin to the
GATE pin is also required. The capacitor controls the slew
rate at the VCC pin, while the resistor limits the inrush
current when the input voltage is first applied. When the
pass transistor turns on, VCC ramps down in a controlled
manner, with a slope equal to 10µA/C. When the pass
transistor turns off, VCC ramps up with a slope of 40µA/C.
A series RC network from the GATE to the VCC pin is
required to control the slew rate at the VCC pin when the
switch is turned on or off. The slew rate control prevents
excessive current from the capacitor located in the wall
adapter from flowing into the battery when the pass
transistor is turned on. The voltage at this pin is internally
clamped to 12V above the BAT pin.
CHRG (Pin 3): Open-Drain Charge Status Output. When a
depleted battery is being charged, the CHRG pin is pulled
to ground by an N-MOSFET capable of driving an LED.
Once the duty cycle at the GATE pin drops below 10%, the
N-MOSFET turns off and a weak 40µA current source to
ground turns on to indicate a near end-of-charge (C/10)
condition. When a time-out occurs or the input supply is
removed, the CHRG pin goes high impedance.
BAT (Pin 8): Battery Sense Input Pin. This pin is clamped
to 4.7V if the battery is disconnected while charging. An
internal resistor divider presets the final float voltage to
4.2V.
GND (Pin 4): Electrical Ground Connection and provides
a thermal path from the IC to the PC board copper. Use
large copper pads and traces for maximum heat transfer.
If the voltage at the BAT pin drops 150mV below final float
voltage after the charge cycle has ended, the timer resets
and a new charge cycle begins.
TIMER (Pin 5): Timer Set Pin. The timer period is set by a
capacitor (CTIMER) to ground. The timer period is:
tTIMER = (CTIMER • 3Hr)/(0.1µF). The minimum ON time,
OFF time and the overcurrent time-out period are all set by
the same timer period.
LTC1730EGN-4
GND (Pins 1, 8, 9, 16): Refer to LTC1730ES8-4.2
SENSE (Pin 2): Refer to LTC1730ES8-4.2
VCC (Pin 3): Refer to LTC1730ES8-4.2
NTC/SHDN (Pin 6): Input to the NTC (Negative Tempera-
ture Coefficient) Thermistor Monitoring and Shutdown
Circuitry.Withanexternal10kΩNTCthermistortoground
and a 1% resistor to VCC, this pin can sense the tempera-
ture of the battery pack and stop charging when the
temperature is out of range. When the voltage at this pin
drops below 0.5 • VCC, or 2V at hot temperature or rises
ACPR (Pin 4): Wall Adapter Present Open-Drain Output.
When the input voltage (wall adapter) is applied to the
LTC1730, this pin is pulled to ground by an internal
1730f
5
LTC1730-4/LTC1730-4.2
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PI FU CTIO S
N-channel MOSFET. This output can sink up to 5mA
suitable for driving an LED.
condition is detected, the FAULT pin is pulled low and
latched.
FAULT (Pin 5): Fault Condition Detection Open-Drain
Output. Thisoutputcansinkupto3mAsuitablefordriving
anexternalLED.TheinternalN-channelMOSFETpullsthis
pin to ground when either one of the following conditions
is detected:
CHRG (Pin 6): Refer to LTC1730ES8-4.2
NC(Pins7,14):NoInternalConnection.Connectingthese
pins to ground will help transfer heat from the package.
TIMER (Pin 10): Refer to LTC1730ES8-4.2
NTC/SHDN (Pin 11): Refer to LTC1730ES8-4.2
1. ThevoltageattheNTCpinisoutofthenormaloperation
range. Thisusuallymeansthebatterypacktemperature
is too high or too low. Once the temperature is back to
normal, the FAULT pin becomes high impedance.
SEL (Pin 12): 4.1V/4.2V Battery Selection Input. Ground-
ing this pin will set the output float voltage to 4.1V, while
connecting to VCC will set the voltage to 4.2V.
2. The BAT pin potential stays below 2.45V for more
than 1/4 of the programmed charge time. When this
GATE (Pin 13): Refer to LTC1730ES8-4.2
BAT (Pin 15): Refer to LTC1730ES8-4.2
W
BLOCK DIAGRA
V
CC
CHRG
100mV
+
–
C5
+
35mA
N1
SENSE
GATE
–
40µA
Q-PUMP
(3X)
+
40mV
0.125R
–
C/10
STOP
I
MAX
N
SW
C6
C7
C8
C4
–
+
+
COLD
ACPR
BAT
–
0.375R
R1
R2
R3
C3
C2
C1
NTC/SHDN
–
+
–
LOGIC
HOT
V
MAX
+
0.5R
+
–
–
+
SHDN
V
BAT
121mV
OSCILLATOR
CLK
–
+
FAULT
ACPR
V
MIN
R5
FAULT
C9
SEL
ON
RECHRG
R4
+
–
4.1V/4.2V
1.21V
+
150mV
–
1703 BD
TIMER
GND
1730f
6
LTC1730-4/LTC1730-4.2
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OPERATIO
The LTC1730 is a complete lithium-ion battery pulse
charger with an internal 0.35Ω N-MOSFET switch driven
by an internal charge pump. The charge current is set by
the current limit of the input supply (wall adapter). An
external RSENSE sets the maximum allowable charge over
current (IMAX = 0.1V/RSENSE) and prevents a wall adapter
with the wrong current limit from damaging the battery. If
the current limit of the input supply is above IMAX, the
chargingwillbeimmediatelyterminatedandwillretryafter
400ms (CTIMER = 0.1µF). If the battery is disconnected
while in fast charge mode, the N-channel MOSFET turns
off when the voltage at the BAT pin rises above 4.7V, and
turns back on when the voltage drops below the float
voltage.
When the battery voltage reaches the final float voltage,
the pass transistor turns off for 100ms (minimum off-
time). It remains off as long as the battery voltage stays
above the float voltage after the 100ms off-time. After the
minimum off-time, if the battery voltage drops below the
float voltage, the pass transistor turns back on for at least
380ms(minimumon-time).Asthebatteryapproachesfull
charge, the off-time will get longer and the on-time will
stay at 380ms. The voltage at the BAT pin will be slightly
higher than the final float voltage due to the ESR associ-
ated with the battery pack. This voltage level should not
turn on the overvoltage protection circuitry often located
in the battery pack. When the duty cycle at the GATE pin
drops below 10%, a comparator turns off the N-FET at the
CHRG pin and connects a weak current source (40µA) to
ground to indicate a near end-of-charge (C/10) condition.
The pulse charging will continue until the timer stops.
AchargecyclebeginswhenthevoltageattheVCC pinrises
above the BAT pin by 40mV and the voltage at the NTC/
SHDN pin is in between 0.5 • VCC and 0.875 • VCC. The
charger will go into trickle charge mode if the battery
voltageisbelow2.45V. Thetricklechargecurrentispreset
to 35mA and is provided by an internal current source. In
trickle mode, the charge pump and pass transistor are off.
AnexternalcapacitorattheTIMERpinsetsthetotalcharge
time, the minimum on- and off-time and the overcurrent
retry period. After a time-out has occurred, the charge
cycle is terminated and the CHRG pin is forced high
impedance. To restart the charge cycle, momentarily pull
theNTC/SHDNpinbelow50mVorremoveandreapplythe
input voltage. After the charging stops, if the battery
voltage drops 150mV below the final float voltage, due to
external loading or internal leakage, a new charge cycle
will automatically begins.
When the battery voltage exceeds 2.45V, the charger goes
into the fast charge mode. In this mode, the charge pump
turns on and ramps up the gate voltage of the pass
transistor turning it on. The voltage at the VCC pin then
ramps down to VBAT plus the voltage drop across the pass
transistor and RSENSE, thus reducing the power dissipa-
tion in the pass transistor. The charge current is deter-
mined by the current limit of the input supply.
The charger can be shut down by pulling the NTC/SHDN
pin to ground. When the input voltage is not present, the
charger goes into a sleep mode, dropping battery drain
current to less than 1µA.
1730f
7
LTC1730-4/LTC1730-4.2
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APPLICATIO S I FOR ATIO
an external capacitor from the TIMER pin to ground. The
total charge time is:
Stop Charging
The charger is off when any of the following conditions
exist. The voltage at the VCC pin is less than 40mV above
VBAT (sleep mode), or the potential at the NTC/SHDN pin
is less than 50mV (shutdown mode). The trickle charge
current source and the internal pass transistor are turned
off. The internal resistor divider is disconnected to reduce
the current drain on the battery when in sleep mode.
Time (Hours)= (3 Hour)(CTIMER/0.1µF)
The timer starts when the input voltage (at least 40mV
greater than VBAT) is applied and the potential at the NTC/
SHDN pin is between 0.5 • VCC and 0.875 • VCC. After a
time-out has occurred, the charging stops and the CHRG
pin becomes high impedance.
Input Voltage (Wall Adapter)
CHRG Status Output Pin
The input voltage to the LTC1730 must have some
method of current limit capability. The current limit level
of the input power source must be lower than the
This open-drain output requires a pull-up resistor and can
be used to indicate three charging conditions. When fast
charging begins, an N-FET (capable of driving an LED)
turns on, pulling this pin to ground. Once the duty cycle at
the GATE pin drops below 10%, the N-FET turns off and a
40µA current source to ground turns on. When a time-out
occurs or the input supply is removed, the CHRG pin goes
highimpedanceindicatingthatthechargecyclehasended.
By using two different value resistors, a microprocessor
can detect three states from this pin: charging, C/10 and
stop charging (see Figure 1).
overcurrent limit (IMAX) set by the sense resistor (IMAX
=
100mV/RSENSE). If a wall adapter without current limit is
used, or the current limit level is above IMAX, the charger
will turn on briefly and then immediately turn off after the
overcurrent condition is detected. This cycle will be re-
sumedevery400ms(CTIMER =0.1µF)untilthetotalcharge
time has run out. If overcurrent protection is not needed,
short the SENSE pin to VCC.
+
V
V
DD
Trickle Charge and Defective Battery Detection
2
At the begining of the charge cycle, if the cell voltage is low
(less than 2.45V) the charger goes into a 35mA trickle
charge mode. If the low cell voltage persists for one
quarter of the total charge time, the battery is considered
defective and the charge cycle is terminated. The CHRG
pin output is then forced to a high impedance state.
V
CC
620k
2k
LTC1730
CHRG
MICROPROCESSOR
OUT
3
IN
1730 F01
Figure 1. Interfacing with Microprocessor
Battery Charge Current
When the LTC1730 is in charge mode, the CHRG pin is
pulled to ground by an internal N-MOSFET. To detect this
mode, force the digital output pin, OUT, high and measure
the voltage at the CHRG pin. The N-MOSFET will pull the
pin low even with a 2k pull-up resistor. Once the charge
current drops below 10% of the full scale current (C/10),
the N-MOSFET is turned off and a 40µA current source is
connected to the CHRG pin. By forcing the OUT pin to a
high impedance state, the current source will pull the pin
lowthroughthe620kresistor. Whentheinternaltimerhas
expired, the CHRG pin becomes high impedance and the
620kresistorwillpullthepinhightoindicatethatcharging
The battery charge current is determined by the current
limit of the input supply (wall adapter). However, this
currentmustnotexceedthemaximumchargeovercurrent,
IMAX. If an overcurrent condition is detected, the charging
is immediately terminated, the GATE pin is pulled to
ground and the charge pump turns off. The charging will
resume after a 400ms time off (CTIMER = 0.1µF).
Programming the Timer
The programmable timer is used to terminate the charge
and sets the minimum ON/OFF time and the overcurrent
time-off period. The length of the timer is programmed by
has stopped.
1730f
8
LTC1730-4/LTC1730-4.2
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APPLICATIO S I FOR ATIO
10µA/C
40µA/C
End-of-Charge (C/10)
V
CC
The LTC1730 includes a comparator to monitor the duty
cycle at the GATE pin to detect a near end-of-charge
condition. When the duty cycle falls below 10%, the
comparatortripsandturnsofftheN-MOSFETattheCHRG
pin and switches in a weak (40µA) current source to
ground. The end-of-charge comparator is disabled in
trickle charge mode.
40µA/C
GATE
VOLTAGE
10µA/C
40µA/C
1730 TA02
10µA/C
Figure 2. Slew Rate at GATE and VCC Pins
with the RC Network from GATE to VCC
above VBAT, the external N-MOSFET gate to source break-
down voltage should be rated at 20V or more.
Internal Pass Transistor
AnN-channelMOSFET(0.35Ω)isincludedintheLTC1730
as the pass transistor. The gate of the MOSFET is con-
trolled by an internal charge pump. The body is connected
to ground instead of source terminal. There is no body
diode from the BAT pin back to the VCC pin; therefore, no
blocking diode is required in series with the battery or the
inputsupply. Thiswillnotonlyreducethecostbutalsothe
heat generated when in fast charge mode. An internal
thermal shutdown circuit turns off the pass transistor if
the die temperature exceeds approximately 140°C with
5°C of thermal hysteresis.
Battery Temperature Detection
A negative temperature coefficient (NTC) thermistor lo-
cated close to the battery pack can be used to monitor
battery temperature and will not allow charging unless the
batterytemperatureiswithinanacceptablerange. Connect
a 10kΩ thermistor between ground and the NTC/SHDN pin
and a 4.1k resistor from the NTC/SHDN pin to VCC. If the
temperature rises to 50°C, the resistance of the thermister
will be approximately 4.1kΩ (Dale NTHS-1206N02) and
the LTC1730 will go into a hold mode. For cold tempera-
tures, the threshold of the hold mode is at 0°C (RNTC
≈
Gate Drive
28kΩ). The pass transistor turns off and the timer is frozen
at hold mode while the output status at the CHRG pin
remains the same. The charge cycle begins or resumes
once the temperature is within the acceptable range.
Thepasstransistorgatedriveconsistsofaregulated10µA
current source charge pump. A series RC network is
required from the GATE pin to the VCC pin. When the pass
transistor is turned on, the voltage at the VCC pin starts
slewing down to a voltage equal to VBAT plus the voltage
drop across the pass transistor and RSENSE. The slew rate
is equal to 10µA/C. By ramping the VCC pin down slowly,
the inrush current is reduced. The resistor in series with
thecapacitorisrequiredtolimitthetransientcurrentwhen
the input supply is first applied.
Thermal Considerations
The power handling capability is limited by the maximum
rated junction temperature (125°C) and the amount of PC
board copper used as a heat sink. The power dissipated by
the device consists of two components:
1. Input supply current multiplied by the input voltage
When the charge pump is turned off, a 40µA current
source to ground starts pulling the GATE voltage down.
Once the pass transistor is off, the voltage at the VCC pin
begins slewing up with the rate equal to 40µA/C. With this
external capacitor, the voltage at the VCC pin is ramping at
a controlled manner (Figure 2).
2. The voltage drop across the switch (SENSE pin to BAT
pin) multiplied by the charge current
The LTC1730 has internal thermal shutdown designed to
protect the IC from overtemperature conditions. For con-
tinuous charging in the fast charge mode, the maximum
junction temperature must not be exceeded. It is important
to give careful consideration to all sources of thermal
resistancefromjunctiontoambient.Additionalheatsources
mounted nearby must also be considered.
ForhighercurrentapplicationsanexternalpowerN-MOSFET
can be connected in parallel with the internal pass transis-
tor. Because the charge pump output is clamped to 12V
1730f
9
LTC1730-4/LTC1730-4.2
U
W
U U
APPLICATIO S I FOR ATIO
Table 1. SO-8 Package Thermal Resistance
COPPER AREA TOTAL THERMAL RESISTANCE
TOPSIDE BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
Surfacemountpackagesrelyprimarilyonthecopperleads
(pins) to conduct the heat from the package to the sur-
rounding PC board copper which is acting as a heat sink.
The ground pin is especially important for conducting heat
as well as providing an electrical connection. Use gener-
ous amounts of copper around the ground pin and also
consider feedthrough vias (plated through holes) to back-
sideorinnercopperlayerstomaximizepowerdissipation.
2
2
2
2
2
2
2
2500mm
1000mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
80°C/W
80°C/W
85°C/W
2
2
250mm
*Device is mounted on topside.
Output Voltage Selection (LTC1730EGN-4)
Table 1 lists the thermal resistance for the SO-8 package.
Measured values of thermal resistance for several differ-
ent board sizes and copper areas are listed. All measure-
ments were taken in still air on 0.062" FR-4 board with one
ounce copper.
The float voltage at the BAT pin can be selected by the SEL
pin. Shorting the SEL pin to ground will set the float
voltage to 4.1V, while connecting it to VCC sets it to 4.2V.
This feature allows the charger to be used with different
types of Li-Ion cells.
Calculating Junction Temperature
ACPR Output Pin (LTC1730EGN-4)
Example: Find the maximum junction temperature for a
battery voltage of 4V (VCC will collapse to approximately
VBAT in the fast charge mode), charge current of 1A and a
maximum ambient temperature of 75°C.
When the input voltage is 40mV higher than the voltage at
the BAT pin, the ACPR pin is pulled low to ground to
indicate that the input supply (wall adapter) is applied.
After the input supply is removed, this pin becomes high
impedance. An internal 80ms delay prevents the LTC1730
from turning off if the voltage at the VCC pin rings and gets
too close to VBAT because of the parasitic inductance.
The power dissipated by the IC is:
P = (IBAT • IBAT • RDS(ON)) + (VCC • ICC)
= (1A • 1A • 0.35Ω) + (4V • 1mA)
= 0.35 + 0.004
FAULT Output Pin (LTC1730EGN-4)
The FAULT pin is pulled to ground when either one of the
following conditions is detected:
= 0.354W
The SO-8 package for the LTC1730 features a special lead
frame with a lower thermal resistance and higher allow-
able power dissipation. The junction-to-ambient thermal
resistance of this package when soldered to a PC board is
approximately 80°C/W depending on the copper area. So
the junction temperature rise above ambient will be
approximately:
1. The voltage at the NTC/SHDN pin is out of the operation
range. With a 10k negative temperature coefficient
thermistor placed near the battery pack, this pin indi-
cates that the temperature of the pack is either too cold
or too hot and the charger is suspended. Once the
temperatureisbacktotheoperationalrange,theFAULT
pin becomes high impedance and the charging re-
sumes.
(0.354W)(80°C/W) = 28.3°C
2. The voltage at the BAT pin stays below 2.45V for 1/4 of
the programmed charge time. If VBAT remains low even
with 35mA of trickle charge current for 1/4 of the total
The maximum junction temperature is equal to the maxi-
mum junction temperature rise above ambient plus the
maximum ambient temperature or:
TJMAX = 75°C + 28.3°C = 103.3°C
1730f
10
LTC1730-4/LTC1730-4.2
U
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APPLICATIO S I FOR ATIO
shutting down the charger. After reset, the charger is
back in the charge mode and the FAULT pin becomes
high impedance again.
charge time, the battery is considered defective. The
charger turns off and the FAULT pin is pulled low. This
pin will stay low until the LTC1730 is reset by either
removing the input power supply or momentarily
U
PACKAGE DESCRIPTIO
GN Package
16-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641)
0.189 – 0.196*
(4.801 – 4.978)
0.009
(0.229)
REF
0.015 ± 0.004
(0.38 ± 0.10)
16 15 14 13 12 11 10 9
× 45°
0.053 – 0.068
(1.351 – 1.727)
0.004 – 0.0098
(0.102 – 0.249)
0.007 – 0.0098
(0.178 – 0.249)
0° – 8° TYP
0.229 – 0.244
(5.817 – 6.198)
0.150 – 0.157**
(3.810 – 3.988)
0.016 – 0.050
(0.406 – 1.270)
0.0250
(0.635)
BSC
0.008 – 0.012
(0.203 – 0.305)
* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
GN16 (SSOP) 1098
1
2
3
4
5
6
7
8
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
0.010 – 0.020
(0.254 – 0.508)
7
5
8
6
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
SO8 1298
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
1
2
3
4
1730f
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
LTC1730-4/LTC1730-4.2
U
TYPICAL APPLICATIO S
Single Cell 4.2V Li-Ion Battery Charger (16-Pin Package)
V
IN
= 5V TO 12V WITH 600mA CURRENT LIMIT
3
4.1k
1k
1k
1k
4.7Ω
V
CC
LTC1730EGN-4
CHRG
10k
1µF
6
4
0.047µF
0.1Ω
2
ACPR
SENSE
GATE
BAT
5
13
15
FAULT
11
0.022µF
NTC/SHDN
V
CC
12
SEL
10k
NTC*
1, 8, 9,16
Li-Ion
BATTERY
GND
NC
TIMER
10
7, 14
0.1µF
*NTC: DALE NTHS-1206N02
1730 TA04
Using External N-MOSFET for Higher Charge Current
V
= 5V TO 12V WITH 2A CURRENT LIMIT
IN
D1
MBRS120T3
2
R2
10k
4.7Ω
V
CC
R4
4.1k
R1
1k
R
SENSE
C3
0.047µF
C1
1µF
25mΩ
LTC1730ES8-4.2
D3
1
SENSE
GATE
BAT
CHARGE
STATUS
3
6
7
Q1
Si2302DS
CHRG
8
NTC/SHDN
0.022µF
Li-Ion
BATTERY
R3
10k
NTC*
TIMER
5
GND
4
C
TIMER
0.1µF
1730 TA03
*NTC: DALE NTHS-1206N02
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1730f
LT/TP 0902 1K • PRINTED IN USA
12 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
LINEAR TECHNOLOGY CORPORATION 2001
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
相关型号:
LTC1730ES8-4.2#TRPBF
LTC1730 - Lithium-Ion Battery Pulse Chargers with Overcurrent Protection; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C
Linear
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