DEMO MANUAL DC086
BATTERY CHARGER
LT1510 Constant-Voltage/
Constant-Current Lithium-Ion
Battery Charger
cells being charged (4.2V, 8.4V or 12.6V). Charging cur-
rent is programmed for 1.3A by resistor R1.
The DC input voltage must be at least 3V greater than the
output voltage. When the input voltage is removed, an
external low current MOSFET (Q1) provides a disconnect
for the output voltage divider resistors and the chip goes
into a sleep mode, draining approximately 3µA from the
battery.
DESCRIPTIO
Demonstration board DC086 is a complete lithium-ion
battery charger designed for 1-, 2- or 3-cell applications
(other rechargeable battery types can also be charged, see
page three). The LT
®
1510 is used in a high efficiency
current mode step-down switching topology, capable of
providing up to 1.5A of charging current. This demo board
uses all surface mount components, resulting in a circuit
occupying approximately 1 square inch of board area with
less than 0.3 in. (7.6mm) height.
Jumpers J1 and J2, located on the demo board, are used
to select the correct charging voltage for the number of
PERFOR A CE SU
PARAMETER
V
IN
Battery Voltage (V
BAT
)
When Charging Terminates
Maximum Battery Charging Current
Note: Good thermal PC board layout techniques are required when operating near maximum power levels to prevent excessive junction temperatures.
Note: For 0.5% battery-voltage accuracy, replace R3 to R8 with 0.1% resistors.
*For V
IN
> 25V, C1 should be replaced with a higher voltage rating capacitor.
TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO
Charging Efficiency
96
94
92
V
CC
= 15V
V
BAT
= 8.4V
EFFICIENCY (%)
90
88
86
84
82
80
0.1
0.3
0.7 0.9 1.1 1.3
BATTERY CHARGING CURRENT (A)
0.5
1.5
DM086 • TPC01
U
WW
U W
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
U W
ARY
LIMITS
V
OUT
+ 3V
≤
V
IN
≤
28V*
4.2
±0.7%
8.4V
±0.7%
12.6V
±0.7%
1.3A
±5%
CONDITIONS
V
IN
= 10V
V
IN
= 15V
V
IN
= 20V
Component Side Demo Board
1
DEMO MANUAL DC086
BATTERY CHARGER
PACKAGE A D SCHE ATIC DIAGRA S
J4
V
IN
D1
MBRS140L
1, 4
L1
CTX33-2
33µH
2, 3
C2
0.22µF
D3
MMBD914
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
R9
1k
C5
0.1µF
C1
10µF
R2
300Ω
C3
1µF
16V
I
BAT
Q1
2N7002
J2
V
IN
D2
MBRS140L
J3
GND
GND
SW
BOOST
GND
OVP
SENSE
GND
GND
LT1510
GND
V
CC
V
CC
PROG
V
C
BAT
GND
GND
J1
R3
4.99k
0.25%
R4
R5
R6
R7
R8
3.52k 4.99k 3.52k 4.99k 3.52k
0.25% 0.25% 0.25% 0.25% 0.25%
PROGRAM OUTPUT VOLTAGE
BATTERY
J1
J2
VOLTAGE
CLOSED CLOSED
4.2V
CLOSED OPEN
8.4V
OPEN
OPEN
12.6V
DM086 • SCHEMATIC
Figure 1. Demo Board Schematic
PARTS LIST
REFERENCE
DESIGNATOR
C1
C2
C3
C4
C5
D1, D2
D3
J1, J2
J3 to J6
L1
Q1
R1
R2
R3, R5, R7
R4, R6, R8
R9
U1
QUANTITY
1
1
1
1
1
2
1
2
4
1
1
1
1
3
3
1
1
PART NUMBER
1E106ZY5U-C304F-T
THCS50EIE106Z
12063C224MAT2A
1206YG105ZAT2A
TPSD226M025R0200
12065C104MAT2A
MBRS140LT3
MMBD914LT1
TSW-102-07-G-S
1502-2
CTX33-2
2N7002
CR1206F3K83CT
CR32-301J-T
CR1206F4K99CT
CR1206F3K52CT
CR32-102J-T
LT1510CS
DESCRIPTION
10µF 25V 20% Y5U Ceramic Capacitor
0.22µF 25V 20% X7R Ceramic Capacitor
1µF 16V Y5V Ceramic Capacitor
22µF 25V 20% Tantalum Capacitor
0.1µF 50V 20% X7R Ceramic Capacitor
1A 40V Schottky Diode
100V Silicon Diode
0.1"cc, 0.025"sq. 2-Pin Jumper
0.090" Turret Terminal
33µH 2A SMT Inductor
N-Channel MOSFET Transistor
3.83k 1/4W 0.25% Chip Resistor
300Ω 1/8W 5% Chip Resistor
4.99k 1/4W 0.25% Chip Resistor
3.52k 1/4W 0.25% Chip Resistor
1k 1/8W 5% Chip Resistor
SO-16 Battery Charger IC
VENDOR
Tokin
United Chemicon/Marcon
AVX
AVX
AVX
AVX
Motorola
Motorola
Samtech
Keystone
Coiltronics
Siliconix
IRC
AVX
IRC
IRC
AVX
LTC
TELEPHONE
(408) 432-8020
(708) 696-2000
(207) 282-5111
(207) 282-5111
(207) 282-5111
(207) 282-5111
(602) 244-3550
(602) 244-3550
(800) 726-8329
(718) 956-8900
(407) 241-7876
(800) 554-5565
(512) 992-7900
(207) 282-5111
(512) 992-7900
(512) 992-7900
(207) 282-5111
(408) 432-1900
2
W
W
U
TOP VIEW
GND 1
SW 2
BOOST 3
GND 4
R1
3.83k
0.25%
16 GND
15 V
CC2
14 V
CC1
13 PROG
12 V
C
11 BAT
10 GND
9
GND
OVP 5
SENSE 6
GND 7
GND 8
V
BAT
J6
J5
+
C4
22µF
+
Li-Ion
BATTERY
S PACKAGE
16-LEAD PLASTIC SO
LT1510CS
FOUR CORNER PINS ARE FUSED TO
INTERNAL DIE ATTACH PADDLE FOR
HEAT SINKING TO PC BOARD
USE GENEROUS AMOUNTS OF PC BOARD
COPPER AROUND LEADS (SEE LT1510
DATA SHEET AND DESIGN NOTE 124)
DEMO MANUAL DC086
BATTERY CHARGER
OPERATIO
The DC086 demonstration board is intended for evaluat-
ing the LT1510 switching regulator battery charger IC.
Solder terminals are provided for easy hookup to a power
supply and to a lithium-ion battery to be charged. The
correct charging voltage for either 1, 2 or 3 cells is
selectable by a combination of jumpers (J1 and J2) on the
board. See the schematic diagram for jumper information.
Current limit is set for 1.29A by resistor R1.
With a suitable input power supply and a discharged
battery connected to the demo board, the battery will
begin charging at the programmed current limit of 1.29A.
As the battery charges, the voltage rises and approaches
the program voltage of either 4.2V, 8.4V or 12.6V. The
charger will then maintain a constant voltage across the
battery, with the charging current decreasing to zero over
time as the battery reaches a fully charged condition.
The IC goes into a sleep mode when the input voltage is
removed. In the sleep mode, the drain from the battery due
to the LT1510 is approximately 3µA. An additional source
of battery drain is due to the leakage current of Schottky
diode D1. Selecting a low leakage Schottky diode such as
a Motorola MBRD340 or a low leakage 3A silicon diode
can minimize this current drain.
Some lithium-ion battery manufacturers recommend ter-
minating the constant-voltage float mode after the charge
current has dropped below a specific level (typically 50mA
to 100mA) and a specific amount of time has elapsed
(typically from 30 to 90 minutes). This may extend the life
of the battery, but check with the manufacturer of the
battery you are using for details. Included on the board is
an area for breadboarding a timing circuit.
Other Battery Types
Although the demo board was designed for charging
Li-Ion batteries, simple modifications will allow other
battery types to be charged.
Sealed lead-acid batteries are charged using a current-
limited constant voltage. Over a 0°C to 40°C temperature
range, a charge voltage of 2.35V/cell can be used with no
charge termination needed. The maximum charge current
is determined by the battery manufacturer and is typically
0.25C or less. To use the demo board for charging sealed
Note:
C
is the capacity rating of the battery in Ampere-Hours.
U
lead-acid batteries, reprogram the OVP (overvoltage pro-
tection) feedback resistor divider for the correct battery
charging voltage using the following formula:
V
R
F
=
R
3
OUT
– 1
V
REF
where R
F
= total resistance between OVP pin and BAT pin,
V
REF
= 2.465V, select R3 = 4.99k, 1% or less.
Maximum charging current (up to 1.5A) is programmed
by R1 using the following formula:
R1
=
(
2000
)(
2.465
)
I
CHARGE
where 2.465V = reference voltage present at PROG pin.
The maximum charging current (or current limit) is 2000
times the current out of the PROG pin. This current has both
AC and DC components present; therefore, to provide high
DC accuracy, averaging components R2 and C3 are required.
For nickel-cadmium and nickel-metal-hydride batteries,
the normal charging method is constant current. Fast
charging requires some method to detect full charge and
terminate the high charge current. Some methods often
used to indicate full charge include battery temperature
rise and observing battery voltage profile during charging.
LT1510 Step-Down Switching Regulator
The LT1510 is designed for constant-voltage and/or con-
stant-current operation with a 0.5% voltage accuracy and
a 5% current accuracy. An external resistor voltage divider
programs the output voltage, while a single resistor (or a
programming current from a DAC) sets the maximum
charging current .
An internal 2A NPN switch operating at 200kHz provides
high efficiency with low inductor values using a minimum
number of external components. The charging current
sense resistor is included on the die and can be wired for
sensing charging current at either the positive or negative
side of the battery.
Refer to the LT1510 data sheet for complete product
specifications and design notes DN111 and DN124 for
additional application information.
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.
3
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