LT1505 Datasheet, PDF (1/16 Pages) Linear Technology – Constant-Current/Voltage High Efficiency Battery Charger

LT1505
Constant-Current/Voltage
High Efficiency Battery Charger
FEATURES
s _{Simple Charging of Li-Ion, NiMH and NiCd Batteries}
s _{Very High Efficiency: Up to 97%}
s _{Precision 0.5% Charging Voltage Accuracy}
s _{Preset Battery Voltages: 12.3V, 12.6V,}
16.4V and 16.8V
s _{5% Charging Current Accuracy}
s _{Charging Current Programmed by Resistor or DAC}
s _{0.5V Dropout Voltage, Duty Cycle > 99.5%}
s _{AC Adapter Current Limit* Maximizes Charging Rate}
s _{Flag Indicates Li-Ion Charge Completion}
s _{Auto Shutdown with Adapter Removal}
s _{Only 10µA Battery Drain When Idle}
s _{Synchronizable Up to 280kHz}
U
APPLICATIO S
s _{Notebook Computers}
s _{Portable Instruments}
s _{Chargers for Li-Ion, NiMH, NiCd and Lead Acid}
Rechargeable Batteries
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
TYPICAL APPLICATION
V_IN
(FROM
ADAPTER)
R5
4k
R6
4k
M3
Si4435
DBODY*
TO
SYSTEM POWER
R_S4
0.025Ω
R7
500Ω
C1
1µF
C_IN
47µF
35V
100k
V_CC
CLN
CLP
INFET
UV
SYNC
SHDN
BOOST BOOSTC
GBIAS
TGATE
SW
BGATE
LT1505
V_C
PROG
3 CELL
*BODY DIODE
POLARITY MUST
BE AS SHOWN
C6
0.1µF
R1
1k
C7
0.68µF
FLAG
CAP
COMP1
BAT2 BAT
V_FB
4.2V
4.1V
AGND
PGND
SENSE SPIN
C4
0.1µF
D3
MMSD4148T1
C3
D2
2.2µF MMSD4148T1
5Ω
M1
Si4412
M2
Si4412
D4
MBRS140
C2
0.68µF
L1
15µH
R_S1
0.025Ω
C_OUT
22µF
25V
×2
300Ω
C_PROG
1µF
R_PROG
4.93k
1%
R_X4
3k
0.33µF
NOTE: DBODY IS THE BODY DIODE OF M3
C_IN: SANYO OS-CON
L1: SUMIDA CDRH127-150
(CAN BE FROM 10µH TO 30µH)
R_S2
200Ω
1%
R_S3
200Ω
1%
V_BAT
12.6V
BATTERY
1505 F01
Figure 1. Low Dropout 4A Lithium-Ion Battery Charger
1