LTC4008_15 Datasheet, PDF (1/24 Pages) Linear Technology – 4A, High Effi ciency, Multi-Chemistry Battery Charger

LTC4008
4A, High Efficiency,
Multi-Chemistry Battery Charger
FEATURES
n _{General Purpose Charger Controller}
n _{High Conversion Efficiency: Up to 96%}
n _{Output Currents Exceeding 4A}
n _{±0.8% Voltage Accuracy}
n _{AC Adapter Current Limiting Maximizes}
Charge Rate*
n _{Thermistor Input for Temperature Qualified Charging}
n _{Wide Input Voltage Range: 6V to 28V}
n _{Wide Output Voltage: 3V to 28V}
n _{0.5V Dropout Voltage; Maximum Duty Cycle: 98%}
n _{Programmable Charge Current: ±4% Accuracy}
n _{Indicator Outputs for Charging, C/10 Current}
Detection, AC Adapter Present, Input Current
Limiting and Faults
n _{Charging Current Monitor Output}
n _{Available in a 20-Pin Narrow SSOP Package}
APPLICATIONS
n _{Notebook Computers}
n _{Portable Instruments}
n _{Battery Backup Systems}
DESCRIPTION
The LTC^®4008 is a constant-current/constant-voltage
charger controller. The PWM controller uses a synchronous,
quasi-constant frequency, constant off-time architecture
that will not generate audible noise even when using ceramic
capacitors. Charging current is programmable 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 bat-
tery temperature returns to within safe limits; a FAULT pin
indicates this condition. A FLAG pin indicates when charg-
ing current has decreased below 10% of the programmed
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.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and No R_SENSE are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5723970.
TYPICAL APPLICATION
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
FAULT
FLAG
INFET
CLP
CLN
TGATE
BGATE
NTC
PGND
R_T
CSP
I_TH
BAT
GND
PROG
NOTE: * 0.25% TOLERANCE
ALL OTHER RESISTORS ARE 1% TOLERANCE
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
4008 TA01
0.025Ω
SYSTEM
LOAD
Li-Ion
20μF
BATTERY
CHARGING
CURRENT
MONITOR
4008fb
1