LTC4008 Datasheet, PDF (1/24 Pages) Linear Technology – 4A, High Efficiency, Multi-Chemistry Battery Charger

LTC4008
4A, High Efficiency,
Multi-Chemistry Battery Charger
FEATURES
■ _{General Purpose Charger Controller}
■ _{High Conversion Efficiency: Up to 96%}
■ _{Output Currents Exceeding 4A}
■ _{±0.8% Voltage Accuracy}
■ _{AC Adapter Current Limiting Maximizes}
Charge Rate*
■ _{Thermistor Input for Temperature Qualified Charging}
■ _{Wide Input Voltage Range: 6V to 28V}
■ _{Wide Output Voltage: 3V to 28V}
■ _{0.5V Dropout Voltage; Maximum Duty Cycle: 98%}
■ _{Programmable Charge Current: ±4% Accuracy}
■ _{Indicator Outputs for Charging, C/10 Current}
Detection, AC Adapter Present, Input Current
Limiting and Faults
■ _{Charging Current Monitor Output}
■ _{Available in a 20-Pin Narrow SSOP Package}
U
APPLICATIO S
■ _{Notebook Computers}
■ _{Portable Instruments}
■ _{Battery Backup Systems}
DESCRIPTIO
The LTC^®4008 is a constant-current/constant-voltage
charger controller. The PWM controller uses a synchro-
nous, quasi-constant frequency, constant off-time archi-
tecture that will not generate audible noise even when
using ceramic capacitors. Charging current is program-
mable with a sense resistor and programming resistor to
±4% typical accuracy. Charging current can be monitored
as a voltage across the programming resistor. An external
resistor divider and precision internal reference set the
final float voltage.
The LTC4008 includes a thermistor sensor input that will
suspend charging if an unsafe temperature condition is
detected and will automatically resume charging when
battery temperature returns to within safe limits; a FAULT
pin indicates this condition. A FLAG pin indicates when
charging current has decreased below 10% of the pro-
grammed current. An external sense resistor programs
AC adapter current limiting. The I_CL pin indicates when the
charging current is being reduced by input current limiting
so that the charging algorithm can adapt.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. Patents including 5723970
TYPICAL APPLICATIO
12.3V, 4A Li-Ion Charger
DCIN
0V TO 28V
V_LOGIC
I_CL
ACP
FAULT
FLAG
100k 100k
THERMISTOR
10k
NTC
150k
0.47µF
140k*
32.4k
15k*
6.04k
0.12µF
LTC4008
BATMON DCIN
V_FB
I_CL
ACP/SHDN
INFET
CLP
CLN
FAULT
TGATE
FLAG
BGATE
NTC
PGND
R_T
CSP
I_TH
BAT
GND
PROG
INPUT SWITCH
0.1µF
0.1µF
4.99k
0.02Ω
20µF
Q1
10µH
Q2
3.01k
3.01k
0.0047µF ^26.7k
Q1: Si4431BDY
Q2: FDC645N
NOTE: * 0.25% TOLERANCE
ALL OTHER RESISTORS ARE 1% TOLERANCE
4008 TA01
0.025Ω
SYSTEM
LOAD
20µF
Li-Ion
BATTERY
CHARGING
CURRENT
MONITOR
4008fa
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