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PDF LTC4006 Data sheet ( Hoja de datos )
| Número de pieza | LTC4006 | |
| Descripción | Standalone Li-Ion Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC4006
4A, High Efficiency,
Standalone Li-Ion
Battery Charger
FEATURES
DESCRIPTIO
■ Complete Charger Controller for 2-, 3- or 4-Cell
Lithium-Ion Batteries
■ High Conversion Efficiency: Up to 96%
■ Output Currents Exceeding 4A
■ ±0.8% Accurate Preset Voltages: 8.4V, 12.6V, 16.8V
■ Built-In Charge Termination with Automatic Restart
■ AC Adapter Current Limiting Maximizes Charge Rate*
■ Automatic Conditioning of Deeply Discharged
Batteries
■ Thermistor Input for Temperature Qualified Charging
■ Wide Input Voltage Range: 6V to 28V
■ 0.5V Dropout Voltage; Maximum Duty Cycle: 98%
■ Programmable Charge Current: ±4% Accuracy
■ Indicator Outputs for Charging, C/10 Current
Detection and AC Adapter Present
■ Charging Current Monitor Output
■ 16-Pin Narrow SSOP Package
U
APPLICATIO S
■ Notebook Computers
■ Portable Instruments
■ Battery-Backup Systems
■ Standalone Li-Ion Chargers
The LTC®4006 is a complete constant-current/constant-
voltage charger controller for 2-, 3- or 4-cell lithium bat-
teries in a small package using few external components.
The PWM controller is a synchronous, quasi-constant fre-
quency, constant off-time architecture that will not gener-
ate audible noise even when using ceramic capacitors.
The LTC4006 is available in 8.4V, 12.6V and 16.8V versions
with±0.8% voltage accuracy. Charging current is program-
mable with a single sense resistor to ±4% typical accuracy.
Charging current can be monitored as a representative
voltage at the IMON pin. A timer, programmed by an external
resistor, sets the total charge time or is reset to 25% of total
charge time after C/10 charging current is reached. Charg-
ing automatically resumes when the cell voltage falls below
3.9V/cell.
Fully discharged cells are automatically trickle charged at
10% of the programmed current until the cell voltage ex-
ceeds 2.5V/cell. Charging terminates if the low-battery
condition persists for more than 25% of the total charge
time.
The LTC4006 includes a thermistor sensor input that
suspends charging if an unsafe temperature condition is
detected and automatically resumes charging when the
battery temperature returns to within safe limits.
, LT, LTC and LTM 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
4A Li-Ion Battery Charger
DCIN
0V TO 28V
3A
VLOGIC
CHG
ACP
CHARGING
CURRENT MONITOR
0.1µF
100k
32.4k
THERMISTOR
10k
NTC
0.0047µF
0.47µF
309k
TIMING
RESISTOR
(~2 HOURS)
0.12µF
6k
INPUT SWITCH
DCIN
INFET
LTC4006
CHG CLP
ACP/SHDN CLN
IMON
NTC
TGATE
BGATE
RT PGND
ITH CSP
GND BAT
5k
15nF
0.033Ω
20µF
10µH
TO SYSTEM LOAD
0.025Ω
BATTERY
20µF
4006 TA01
4006fa
1
1 page  
LTC4006
TYPICAL PERFOR A CE CHARACTERISTICS
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
LTC4006-2
Efficiency at 19VDC VIN
100
LTC4006-4
95
LTC4006-2
90
4006 G04
Battery Leakage Current vs
Battery Voltage
40
VDCIN = 0V
35
30
25
20
15
10
5
0
0 5 10 15 20 25 30
BATTERY VOLTAGE (V)
4006 G05
LTC4006-2 Efficiency with
15VDC VIN
100
95
90
85 85
80 80
75
0.50
1.00 1.50 2.00 2.50 3.00
CHARGING CURRENT (A)
4006 G07
75
0.50
1.00 1.50 2.00 2.50 3.00
CHARGING CURRENT (A)
4006 G08
PI FU CTIO S
DCIN (Pin 1): External DC Power Source Input. Bypass
this pin with at least 0.01µF. See Applications Information
section.
CHG (Pin 2): Open-Drain Charge Status Output. When the
battery is being charged, the CHG pin is pulled low by an
internal N-channel MOSFET. When the charge current
drops below 10% of programmed current, the N-channel
MOSFET turns off and a 25µA current source is connected
from the CHG pin to GND. When the timer runs out or the
input supply is removed, the current source will be discon-
nected and the CHG pin is forced into a high impedance
state. A pull-up resistor is required. The timer function is
defeated by forcing this pin below 1V (or connecting it to
GND).
ACP/SHDN (Pin 3): Open-Drain Output used to indicate if
the AC adapter voltage is adequate for charging. Active
high digital output. Internal 10µA pull-up to 3.5V. The
charger can also be inhibited by pulling this pin below 1V.
Reset the charger by pulsing the pin low for a minimum of
0.1µs.
4006fa
5
5 Page 
U
OPERATIO
be inhibited if it is not already active. If the charging current
decreases below 10% to 15% of programmed current,
while engaged in input current limiting, BGATE will be
forced low to prevent the charger from discharging the
battery. Audible noise can occur in this mode of operation.
An overvoltage comparator guards against voltage tran-
sient overshoots (>7% of programmed value). In this
case, both MOSFETs are turned off until the overvoltage
condition is cleared. This feature is useful for batteries
which “load dump” themselves by opening their protec-
tion switch to perform functions such as calibration or
pulse mode charging.
As the voltage at BAT increases to near the input voltage
at DCIN, the converter will attempt to turn on the top
MOSFET continuously (“dropout’’). A watchdog timer
detects this condition and forces the top MOSFET to turn
off for about 300ns at 40µs intervals. This is done to
prevent audible noise when using ceramic capacitors at
the input and output.
Charger Startup
When the charger is enabled, it will not begin switching
until the ITH voltage exceeds a threshold that assures initial
current will be positive. This threshold is 5% to 15% of the
maximum programmed current. After the charger begins
switching, the various loops will control the current at a
level that is higher or lower than the initial current. The
duration of this transient condition depends upon the loop
compensation but is typically less than 100µs.
Thermistor Detection
The thermistor detection circuit is shown in Figure 3. It requires
an external resistor and capacitor in order to function properly.
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 = 13.8ms,
for RRT = 309k
The external RC network is driven to approximately 4.5V
and settles to a final value across the thermistor of:
VRTH(FINAL)
=
4.5V
RTH
• RTH
+ R9
LTC4006
LTC4006
R9
32.4k NTC
6
RTH
10k
NTC
C7
0.47µF
S1
–
~4.5V
+
CLK
60k
+
–
–
+
DQ
C
Figure 3
45k
15k
TBAD
4006 F03
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 = 54µs,
for RRT = 309k
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, 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
4006 F04
Figure 4
4006fa
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC4006.PDF ] | |
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