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PDF LTC4002-4.2 Data sheet ( Hoja de datos )
| Número de pieza | LTC4002-4.2 | |
| Descripción | Standalone Li-Ion Switch Mode Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Final Electrical Specifications
LTC4002-4.2
Standalone Li-Ion
Switch Mode Battery Charger
FEATURES
DESCRIPTIO
June 2003
s Wide Input Supply Range: 4.7V to 24V
s High Efficiency Current Mode PWM Controller with
500kHz Switching Frequency
s ±1% Charge Voltage Accuracy
s End-of-Charge Current Detection Output
s 3 Hour Charge Termination Timer
s Constant Switching Frequency for Minimum Noise
s ±5% Charge Current Accuracy
s Low 10µA Reverse Battery Drain Current
s Automatic Battery Recharge
s Automatic Shutdown When Input Supply is Removed
s Automatic Trickle Charging of Low Voltage Batteries
s Battery Temperature Sensing and Charge
Qualification
s Stable with Ceramic Output Capacitor
s 8-Lead SO and 10-Lead DFN Packages
U
APPLICATIO S
s Portable Computers
s Charging Docks
s Handheld Instruments
The LTC®4002-4.2 is a complete battery charger controller
for single cell 4.2V lithium-ion batteries. With a 500kHz
switching frequency, the LTC4002-4.2 provides a small,
simple and efficient solution to fast charge Li-Ion batteries
from a wide range of supply voltages. An external sense
resistor sets the charge current with ±5% accuracy. An
internal resistor divider and precision reference set the
final float voltage to 4.2V with ±1% accuracy.
When the input supply is removed, the LTC4002-4.2
automatically enters a low current sleep mode, dropping
the battery drain current to 10µA. An internal comparator
detects the near end-of-charge condition while an internal
timer sets the total charge time and terminates the charge
cycle. After the charge cycle ends, if the battery voltage
drops below 4.05V, a new charge cycle will automatically
begin.
The LTC4002-4.2 is available in the 8-lead SO and 10-lead
DFN packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
5V TO 24V
B330B-13
CHARGE
STATUS
BAT
2k
0.1µF
CER
2
VCC
3
GATE
Si6435ADQ
10µF
CER
LTC4002ES8-4.2
57
CHRG SENSE
L1
6.8µH
B330B-13
1
0.47µF
2.2k
68mΩ
COMP
BAT 6
NTC GND
84
22µF
CER
+ Li-Ion
BATTERY
T
10k
NTC
400242 F01
NTC: DALE NTHS-1206N02
Figure 1. 1.5A Single Cell Li-Ion Battery Charger
Efficiency vs Input Voltage
100
ICHRG = 1.5A
RSENSE = 68mΩ
(CURVES INCLUDE
90 INPUT DIODE)
VBAT = 4V
80 VBAT = 3.8V
70
60
5
10 15 20
INPUT VOLTAGE (V)
25
400242 TA02
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
400242i
1
1 page  
LTC4002-4.2
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C, VCC = 10V unless otherwise noted.
Trickle Charge Sense Voltage
vs Temperature
10.4
VBAT = 2.5V
Trickle Charge Sense Voltage
vs VCC
11
VBAT = 2.5V
COMP Pin Output Current
vs VCC
102
VCOMP = 0V
10.0 10 100
9.6
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
400242 G12
COMP Pin Output Current
vs Temperature
104
VCOMP = 0V
9
5 10 15 20 25
VCC (V)
400242 G13
NTC Pin Output Current
vs VCC
86
VNTC = 0V
98
5
10 15 20 25
VCC (V)
400242 G14
NTC Pin Output Current
vs Temperature
89
VNTC = 0V
100 85 85
96
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
400242 G15
Recharge Voltage Offset from Full
Charged Voltage vs Temperature
190
84
5
10 15 20 25
VCC (V)
400242 G16
Recharge Voltage Offset from Full
Charged Voltage vs VCC
160
81
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
400242 G17
End-of-Charge Ratio
vs Temperature
29
150 150
25
110
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
400242 G18
140
5
10 15 20 25
VCC (V)
400242 G19
21
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
400242 G20
400242i
5
5 Page 
LTC4002-4.2
APPLICATIO S I FOR ATIO
Gate Drive
The LTC4002-4.2 gate driver can provide high transient
currents to drive the external pass transistor. The rise and
fall times are typically 20ns and 50ns respectively when
driving a 2000pF load, which is typical for a P-channel
MOSFET with RDS(ON) in the range of 50mΩ.
A voltage clamp is added to limit the gate drive to 8V below
VCC. For example, if VCC is 10V then the GATE output will
pull down to 2V max. This allows low voltage P-channel
MOSFETs with superior RDS(ON) to be used as the pass
transistor thus increasing efficiency.
Stability
Both the current loop and the voltage loop share a com-
mon, high impedance, compensation node (COMP pin). A
series capacitor and resistor on this pin compensates both
loops. The resistor is included to provide a zero in the loop
response and boost the phase margin.
The compensation capacitor also provides a soft-start
function for the charger. Upon start-up, the COMP pin
voltage will quickly rise to 0.05V, due to the 2.2k series
resistor, then ramp at a rate set by the internal 100µA pull-
up current source and the external capacitor. Battery
charge current starts ramping up when the COMP pin
voltage reaches 0.8V and full current is achieved with the
COMP pin at 1.3V. With a 0.47µF capacitor, time to reach
full charge current is about 235ms. Capacitance can be
increased up to 1µF if a longer start-up time is needed.
Automatic Battery Recharge
After the 3 hour charge cycle is completed and both the
battery and the input power supply (wall adapter) are still
connected, a new charge cycle will begin if the battery
voltage drops below 4.05V due to self-discharge or exter-
nal loading. This will keep the battery capacity at more than
80% at all times without manually restarting the charge
cycle.
Battery Temperature Detection
A negative temperature coefficient (NTC) thermistor
located close to the battery pack can be used to monitor
battery temperature and will not allow charging unless the
battery temperature is within an acceptable range.
Connect a 10kΩ thermistor (DALE NTHS-1206N02) from
the NTC pin to ground. If the temperature rises to 50°C, the
resistance of the NTC will be approximately 4.1kΩ. With
the 85µA pull-up current source, the Hot temperature
voltage threshold is 350mV. For Cold temperature, the
voltage threshold is set at 2.456V which is equal to 0°C
(RNTC ≅ 28.4kΩ) with 85µA of pull-up current. If the
temperature is outside the window, the GATE pin will be
pulled up to VCC and the timer frozen while the output
status at the CHRG pin remains the same. The charge cycle
begins or resumes once the temperature is within the
acceptable range. Short the NTC pin to ground to disable
the temperature qualification feature.
400242i
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4002-4.2.PDF ] | |
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