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PDF LTC4008 Data sheet ( Hoja de datos )
| Número de pieza | LTC4008 | |
| Descripción | Multi-Chemistry Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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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*
www■.DaTthaeSrhmeeist4tUo.rcIonmput 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 ICL 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
VLOGIC
ICL
ACP
FAULT
FLAG
100k 100k
THERMISTOR
10k
NTC
150k
0.47µF
140k*
32.4k
15k*
6.04k
0.12µF
LTC4008
BATMON DCIN
VFB
ICL
ACP/SHDN
INFET
CLP
CLN
FAULT
TGATE
FLAG
BGATE
NTC PGND
RT CSP
ITH 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
1
1 page  
LTC4008
TYPICAL PERFOR A CE CHARACTERISTICS (TA = 25°C unless otherwise noted)
VOUT vs IOUT
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
www.Da–4t.a0 Sheet4U.com
–4.5 DCIN = 20V
VBAT = 12.6V
–5.0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
OUTPUT CURRENT (A)
4008 G04
PWM Frequency vs Duty Cycle
350
300
250
200
150
PROGRAMMED CURRENT = 10%
100
50 DCIN = 15V
DCIN = 20V
0 DCIN = 24V
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
DUTY CYCLE (VOUT/VIN)
4008 G05
Disconnect/Reconnect Battery
(Load Dump)
VFLOAT
1V/(DIV)
3A STEP
1A STEP
1A STEP
LOAD
STATE
DISCONNECT
3A STEP
RECONNECT
LOAD CURRENT = 1A, 2A, 3A
DCIN = 20V
VFLOAT = 12.6V
4008 G06
Battery Leakage Current vs
Battery Voltage
40
VDCIN = 0V
35
30
25
20
15
Efficiency at 19VDC VIN
100
16.8V
95
12.6V
90
85
10
80
5
0
0 5 10 15 20 25 30
BATTERY VOLTAGE (V)
4008 G07
75
0.50
1.00 1.50 2.00 2.50 3.00
CHARGE CURRENT (A)
4008 G09
Efficiency at 12.6V with 15VDC VIN
100
95
90
85
80
75
0.50
1.00 1.50 2.00 2.50 3.00
CHARGE CURRENT (A)
4008 G10
Charging Voltage Error
TEMP = 27°C, ILOAD = 0.120A
0.150
0.125
0.100
0.075
0.050
DCIN = 20V
0.025
DCIN = 15V
0
–0.025
–0.050
–0.075
–0.100
–0.125
–0.150
0 2 4 6 8 10 12 14 16 18 20 22
CHARGING VOLTAGE (V)
4008 G11
4008fa
5
5 Page 
U
OPERATIO
The thermistor detector performs a sample-and-hold func-
tion. An internal clock, whose frequency is determined by
the timing resistor connected to RT, keeps switch S1
closed to sample the thermistor:
tSAMPLE = 127.5 • 20 • RRT • 17.5pF = 6.7ms,
for RRT = 150k
The external RC network is driven to approximately 4.5V
and settles to a final value across the thermistor of:
www.DaVtRaTShHe(FeItN4AUL.c) o=mR4.T5HV+•
RTH
R10
LTC4008
This voltage is stored by C7. Then the switch is opened for
a short period of time to read the voltage across the
thermistor.
tHOLD = 10 • RRT • 17.5pF = 26µs,
for RRT = 150k
When the tHOLD interval ends the result of the thermistor
testing is stored in the D flip-flop (DFF). If the voltage at
NTC is within the limits provided by the resistor divider
feeding the comparators, then the NOR gate output will be
low and the DFF will set TBAD to zero and charging will
continue. If the voltage at NTC is outside of the resistor
divider limits, then the DFF will set TBAD to one, the charger
will be shut down, FAULT pin is set low and the timer will
be suspended until TBAD returns to zero (see Figure 4).
CLK
(NOT TO
SCALE)
tSAMPLE
tHOLD
VOLTAGE ACROSS THERMISTOR
VNTC
COMPARATOR HIGH LIMIT
COMPARATOR LOW LIMIT
Figure 4
4008 F04
4008fa
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11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC4008.PDF ] | |
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