FEATURES
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LT1505
Constant-Current/Voltage
High Efficiency Battery Charger
DESCRIPTIO
The LT
®
1505 PWM battery charger controller fast charges
multiple battery chemistries including lithium-ion (Li-Ion),
nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd)
using constant-current or constant-voltage control. Maxi-
mum current can be easily programmed by resistors or a
DAC. The constant-voltage output can be selected for 3 or 4
series Li-Ion cells with 0.5% accuracy.
A third control loop limits the current drawn from the AC
adapter during charging*. This allows simultaneous opera-
tion of the equipment and fast battery charging without over-
loading the AC adapter.
The LT1505 can charge batteries ranging from 2.5V to 20V
with dropout voltage as low as 0.5V. Synchronous
N-channel FETs switching at 200kHz give high efficiency
and allow small inductor size. A diode is not required in
series with the battery because the charger automatically
enters a 10µA sleep mode when the wall adapter is un-
plugged. A logic output indicates Li-Ion full charge when
current drops to 20% of the programmed value.
The LT1505 is available in a 28-pin SSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*US Patent No. 5,723,970
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Simple Charging of Li-Ion, NiMH and NiCd Batteries
Very High Efficiency: Up to 97%
Precision 0.5% Charging Voltage Accuracy
Preset Battery Voltages: 12.3V, 12.6V,
16.4V and 16.8V
5% Charging Current Accuracy
Charging Current Programmed by Resistor or DAC
0.5V Dropout Voltage, Duty Cycle > 99.5%
AC Adapter Current Limit* Maximizes Charging Rate
Flag Indicates Li-Ion Charge Completion
Auto Shutdown with Adapter Removal
Only 10µA Battery Drain When Idle
Synchronizable Up to 280kHz
APPLICATIO S
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Notebook Computers
Portable Instruments
Chargers for Li-Ion, NiMH, NiCd and Lead Acid
Rechargeable Batteries
TYPICAL APPLICATION
M3
Si4435
DBODY*
V
IN
(FROM
ADAPTER)
TO
SYSTEM POWER
R
S4
0.025Ω
C1
1µF
C
IN
47µF
35V
V
CC
BOOST
BOOSTC
GBIAS
CLN
CLP
INFET
UV
R6
4k
SYNC
SHDN
FLAG
*BODY DIODE
POLARITY MUST
BE AS SHOWN
C6
0.1µF
CAP
COMP1
R1
1k
C7
0.68µF
BAT2 BAT
SENSE
LT1505
TGATE
SW
BGATE
V
C
PROG
3 CELL
V
FB
4.2V
4.1V
AGND
PGND
SPIN
300Ω
C
PROG
1µF
R
PROG
4.93k
1%
R
X4
3k
0.33µF
R
S2
200Ω
1%
R
S3
200Ω
1%
5Ω
C3
D2
2.2µF MMSD4148T1
M1
Si4412
M2
Si4412
D4
MBRS140
C4
0.1µF
D3
MMSD4148T1
C2
0.68µF
L1
15µH
R
S1
0.025Ω
V
BAT
C
OUT
22µF
25V
×
2
12.6V
BATTERY
R7
500Ω
100k
R5
4k
NOTE: DBODY IS THE BODY DIODE OF M3
C
IN
: SANYO OS-CON
L1: SUMIDA CDRH127-150
(CAN BE FROM 10µH TO 30µH)
1505 F01
Figure 1. Low Dropout 4A Lithium-Ion Battery Charger
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1
LINER [ LINEAR TECHNOLOGY ]
