LTC1730-4/LTC1730-4.2
1
1730f
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
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, virtually eliminating heat generation in the charger.
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 1
A (maximum).
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.
The LTC1730-4 is available in the 16-pin SSOP package
and the LTC1730-4.2 is available in the 8-pin SO package.
s
Standalone Lithium-Ion Battery Charger
s
Handheld Computers
s
Cellular Telephones
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
Complete Pulse Charger for 1-Cell Lithium-Ion
Batteries
s
Sense Resistor Limits Maximum Current for Safety
s
1% Float Voltage Accuracy
s
End-of-Charge (C/10) Detection Output
s
Programmable Charge Termination Timer
s
Internal 0.35
NMOS Switch
s
No Blocking Diode Required
s
SEL Pin to Set Either 4.1V or 4.2V/Cell (LTC1730-4)
s
Low-Battery Drain (1
A Max) when Input Supply Is
Removed
s
Battery Temperature Sensing and Charge
Qualification
s
Automatic Trickle Charge for Low-Battery
s
Automatic Battery Refresh
Lithium-Ion Battery
Pulse Charger with
Overcurrent Protection
R1
1k
R2
10k
4.7
R
SENSE
0.05
1-CELL
Li-Ion
BATTERY
D3
R3
4.1k
CHRG
NTC/SHDN
GATE
BAT
TIMER
C
TIMER
0.1
F
GND
5
4
V
IN
2
LTC1730ES8-4.2
SENSE
C1
1
F
C3
0.047
F
0.022
F
3
6
1
7
8
V
IN
= 4.5V TO 12V
WITH 1A CURRENT LIMIT
CHARGE STATUS
1730 TA01
R4
10k
NTC*
T
*NTC: DALE NTHS-1206N02
1A, Single Cell 4.2V Li-Ion Battery Charger (8-Pin Package)
LTC1730-4/LTC1730-4.2
2
1730f
Supply Voltage (V
CC
) ............................................ 13.2V
SENSE, GATE, BAT,
TIMER, NTC/SHDN, SEL ............................ 0.3V to V
CC
CHRG, ACPR, FAULT .............................. 0.3V to 13.2V
ORDER PART
NUMBER
S8 PART MARKING
T
JMAX
= 125
C,
JA
= 110
C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
173042
LTC1730ES8-4.2
ABSOLUTE AXI U
RATI GS
W
W
W
U
(Note 1)
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 6V unless otherwise noted.
1
2
3
4
8
7
6
5
TOP VIEW
BAT
GATE
CHRG
TIMER
SENSE
ACPRB
V
IN
GND
S8 PACKAGE
8-LEAD PLASTIC SO
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Supply Voltage
q
4.5
12
V
I
CC
Supply Current
Charger On; Fast Charge Mode
q
2
5
mA
Shutdown: V
NTC/SHDN
= 0V
q
2
5
mA
Sleep Mode; V
BAT
= 4V
q
1
A
V
BAT
Regulated Output Voltage
LTC1730ES8-4.2 (5V
V
CC
12V)
q
4.158
4.2
4.242
V
LTC1730EGN-4 (5V
V
CC
12V), SEL = GND
q
4.059
4.1
4.141
V
LTC1730EGN-4 (5V
V
CC
12V), SEL = V
CC
q
4.158
4.2
4.242
V
I
MAX
Maximum Charge Overcurrent
R
SENSE
= 0.1
q
0.7
1
1.3
A
I
TRICKL
Trickle Charge Current
V
BAT
= 2V
15
35
60
mA
V
TRICKL
Trickle Charge Trip Threshold
2.45
2.55
V
V
ASD
Automatic Shutdown Threshold Voltage
(V
CC
V
BAT
) Low to High
150
mV
(Sleep Mode)
(V
CC
V
BAT
) High to Low
0
mV
R
DS(ON)
Internal Switch On-Resistance
V
BAT
= 4V
0.35
V
SHDN
Shutdown Threshold Voltage
NTC/SHDN Pin High to Low
50
mV
DC ELECTRICAL CHARACTERISTICS
ORDER PART
NUMBER
LTC1730EGN-4
1
2
3
4
5
6
7
8
TOP VIEW
GN PACKAGE
16-LEAD PLASTIC SSOP
16
15
14
13
12
11
10
9
GND*
SENSE
V
CC
ACPR
FAULT
CHRG
NC**
GND*
GND*
BAT
NC**
GATE
SEL
NTC/SHDN
TIMER
GND*
* 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
T
JMAX
= 125
C,
JA
= 90
C/W
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
GN PART MARKING
17304
LTC1730-4/LTC1730-4.2
3
1730f
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
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
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
CHRG
CHRG Pin Pull-Down Current
V
CHRG
= 1V, C/10 Mode
10
40
70
A
T
TIMER
TIMER Accuracy
C
TIMER
= 0.1
F
10
%
V
GATE
GATE Pin Voltage
V
BAT
= 3V
7.5
V
V
BAT
= 4V
10
V
T
SHDN
Thermal Shutdown Temperature
140
C
T
SHDN
Thermal Shutdown Hysteresis
5
C
V
RECHRG
Recharge Battery Voltage Offset from
V
BAT(Full Charged)
V
RECHRG
(Note 3)
150
mV
Full Charged Battery Voltage
V
NTC_HOT
NTC/SHDN Pin Threshold Voltage (Hot)
High to Low; V
CC
= 4V
q
1.95
2
2.05
V
Hysteresis
50
mV
V
NTC_COLD
NTC/SHDN Pin Threshold Voltage (Cold)
Low to High; V
CC
= 4V
q
3.4
3.5
3.6
V
Hysteresis
45
mV
V
SEL
SEL Pin Threshold
LTC173ECGN-4
0.7
V
V
ACPR
ACPR Pin Output Low Voltage
LTC1730EGN-4, I
ACPR
= 5mA
0.6
V
V
FAULT
FAULT Pin Output Low Voltage
LTC1730EGN-4, I
FAULT
= 3mA
1.2
V
V
CHRG
CHRG Pin Output Low Voltage
I
CHRG
= 5mA, Charging Mode
0.9
V
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 6V unless otherwise noted.
DC ELECTRICAL CHARACTERISTICS
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3: For the LTC1730-4 version, the full charged V
BAT
value is
typically 4.1V.
LTC1730-4/LTC1730-4.2
4
1730f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
V
CC
(V)
5
I (mA)
50
45
40
35
30
25
20
8
10
1730 G01
6
7
9
11
12
TA = 25
C
TEMPERATURE (
C)
50
V
TRIKL
(V)
2.50
2.48
2.46
2.44
2.42
2.40
25
75
1730 G02
25
0
50
100
125
V
CC
= 6V
TEMPERATURE (
C)
50
25
75
1730 G03
25
0
50
100
125
I (mA)
50
45
40
35
30
25
20
V
CC
= 6V
Trickle Charge Current vs Input
Supply Voltage
Trickle Charge Current vs
Temperature
Trickle Charge Threshold Voltage
vs Temperature
TEMPERATURE (
C)
50
25
75
1730 G05
25
0
50
100
125
R
DS(ON)
(
)
0.50
0.45
0.40
0.35
0.30
0.25
0.20
V
BAT
= 4V
TEMPERATURE (
C)
50
25
75
1730 G06
25
0
50
100
125
t
TIMER
(%)
115
110
105
100
95
90
85
80
V
CC
= 6V
C
TIMER
= 0.1
F
TEMPERATURE (
C)
50
25
75
1730 G07
25
0
50
100
125
I
MAX
(A)
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
V
CC
= 6V
R
SEN
= 0.1
TEMPERATURE (
C)
50
25
75
1730 G08
25
0
50
100
125
V
CHRG
(V)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
Timer Accuracy vs Temperature
Internal Switch On-Resistance vs
Temperature
Overcurrent vs Temperature
CHRG Pin Output Low Voltage vs
Temperature
Battery Recharge Threshold Offset
from V
BAT
vs Temperature
TEMPERATURE (
C)
50
25
75
1730 G09
25
0
50
100 125 150
V
RECHRG
(mV)
300
250
200
150
100
50
0
V
CC
= 6V
LTC1730-4/LTC1730-4.2
5
1730f
PI FU CTIO S
U
U
U
LTC1730ES8-4.2
SENSE (Pin 1): Maximum Overcurrent Sense Input. A
sense resistor (R
SENSE
) should be connected from V
CC
to
the SENSE pin. When the voltage drop across R
SENSE
exceeds 100mV, the pass transistor immediately turns off
and turns back on after a 400ms time-out period (C
TIMER
= 0.1
F). 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
V
CC
.
V
CC
(Pin 2): Positive Input Supply Voltage (4.5V
V
CC
13.2V). Bypass this pin with a 1
F capacitor in series with
a 4.7
resistor. An RC network from the V
CC
pin to the
GATE pin is also required. The capacitor controls the slew
rate at the V
CC
pin, while the resistor limits the inrush
current when the input voltage is first applied. When the
pass transistor turns on, V
CC
ramps down in a controlled
manner, with a slope equal to 10
A/C. When the pass
transistor turns off, V
CC
ramps up with a slope of 40
A/C.
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 40
A 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.
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.
TIMER (Pin 5): Timer Set Pin. The timer period is set by a
capacitor (C
TIMER
) to ground. The timer period is:
t
TIMER
= (C
TIMER
3Hr)/(0.1
F). The minimum ON time,
OFF time and the overcurrent time-out period are all set by
the same timer period.
NTC/SHDN (Pin 6): Input to the NTC (Negative Tempera-
ture Coefficient) Thermistor Monitoring and Shutdown
Circuitry. With an external 10k
NTC thermistor to ground
and a 1% resistor to V
CC
, 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 V
CC
, or 2V at hot temperature or rises
above 0.875 V
CC
, or 3.5V at cold (with V
CC
= 4V), the
charge cycle is suspended and the internal timer is frozen.
The CHRG pin output status is not affected in this hold
state.
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
External Pass Transistors. An external N-MOSFET transis-
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 V
CC
is shorted to ground. A 10
A
current source pulls this pin up to the charge pump
potential when turned on and a 40
A 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.
A series RC network from the GATE to the V
CC
pin is
required to control the slew rate at the V
CC
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.
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.
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.
LTC1730EGN-4
GND (Pins 1, 8, 9, 16): Refer to LTC1730ES8-4.2
SENSE (Pin 2): Refer to LTC1730ES8-4.2
V
CC
(Pin 3): Refer to LTC1730ES8-4.2
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
PDF 
ZIP