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PDF LTC4002 Data sheet ( Hoja de datos )
| Número de pieza | LTC4002 | |
| Descripción | Standalone Li-Ion Switch Mode Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC4002
Standalone Li-Ion
Switch Mode Battery Charger
FEATURES
■ Wide Input Supply Range:
4.7V to 22V – 4.2 Version
8.9V to 22V – 8.4 Version
■ High Efficiency Current Mode PWM Controller with
500kHz Switching Frequency
■ ±1% Charge Voltage Accuracy
■ End-of-Charge Current Detection Output
■ 3 Hour Charge Termination Timer
■ Constant Switching Frequency for Minimum Noise
■ ±5% Charge Current Accuracy
■ Low 10µA Reverse Battery Drain Current
■ Automatic Battery Recharge
■ Automatic Shutdown When Input Supply is Removed
■ Automatic Trickle Charging of Low Voltage Batteries
■ Battery Temperature Sensing and Charge
Qualification
■ Stable with Ceramic Output Capacitor
■ 8-Lead SO and 10-Lead DFN Packages
U
APPLICATIO S
■ Portable Computers
■ Charging Docks
■ Handheld Instruments
DESCRIPTIO
The LTC®4002 is a complete battery charger controller for
one (4.2V) or two (8.4V) cell lithium-ion batteries. With a
500kHz switching frequency, the LTC4002 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 per cell with ±1% accuracy.
When the input supply is removed, the LTC4002 automati-
cally 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 per cell, a new charge cycle will automatically begin.
The LTC4002 is available in the 8-lead SO and 10-lead DFN
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
1.5A Single Cell Li-Ion Battery Charger
VIN
5V TO 22V
CHARGE
STATUS
BAT
2k
0.1µF
VCC
GATE
10µF
LTC4002ES8-4.2
CHRG SENSE
6.8µH
68mΩ
0.47µF
2.2k
COMP
NTC
T
BAT
GND
22µF
+ Li-Ion
BATTERY
10k
NTC
4002 TA01
NTC: DALE NTHS-1206N02
Efficiency vs Input Voltage
100
(CURVES INCLUDE
INPUT DIODE)
90
VBAT = 4V
80 VBAT = 3.8V
70
60
5
10 15 20
INPUT VOLTAGE (V)
25
4002 TA02
4002f
1
1 page  
LTC4002
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C, VCC = 10V unless otherwise noted.
Oscillator Frequency vs VCC
510
Undervoltage Lockout Threshold
vs Temperature
8
VCC RISING
LTC4002-8.4
7
CHRG Pin Output Low Voltage
vs VCC
150
ILOAD = 1mA
500 6 140
490
5
10 15 20
VCC (V)
25
4002 G04
CHRG Pin Output Low Voltage
vs Temperature
180
ILOAD = 1mA
5
LTC4002-4.2
4
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
4002 G05
CHRG Pin Weak Pull-Down
Current vs Temperature
29
VCHRG = 8V
130
5
10 15 20
VCC (V)
25
4002 G06
CHRG Output Pin Weak Pull-Down
Current vs VCC
28
VCHRG = 8V
140 25 25
100
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
4002 G07
Recharge Voltage Offset
Per Cell from Full Charged
Voltage vs Temperature
190
21
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
4002 G08
Recharge Voltage Offset from Full
Charged Voltage vs VCC
160
LTC4002-4.2
22
5
10 15 20
VCC (V)
25
4002 G09
Recharge Voltage Offset from Full
Charged Voltage vs VCC
320
LTC4002-8.4
150 150 300
110
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
4002 G10
140
5
10 15 20 25
VCC (V)
4002 G11
280
5
10 15 20 25
VCC (V)
4002 G12
4002f
5
5 Page 
U
OPERATIO
mode, dropping ICC to 10µA. This will greatly reduce the
current drain on the battery and increase the standby time.
A 10kΩ NTC (negative temperature coefficient) thermistor
can be connected from the NTC pin to ground for battery
LTC4002
temperature qualification. The charge cycle is suspended
when the temperature is outside of the 0°C to 50°C
window (with DALE NTHS-1206N02).
APPLICATIO S I FOR ATIO
Undervoltage Lockout (UVLO)
An undervoltage lockout circuit monitors the input voltage
and keeps the charger off until VCC rises above the UVLO
threshold (4.2V for the 4.2 version, 7.5V for the 8.4
version) and at least 250mV above the battery voltage. To
prevent oscillation around the threshold voltage, the UVLO
circuit has 200mV per cell of built-in hysteresis. When
specifying minimum input voltage requirements, the volt-
age drop across the input blocking diode must be added
to the minimum VCC supply voltage specification.
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage is
below the trickle charge threshold, the charger goes into
trickle charge mode with the charge current reduced to
10% of the full-scale current. If the low-battery voltage
persists for 30 minutes, the battery is considered defec-
tive, the charge cycle is terminated and the CHRG pin is
forced high impedance.
Shutdown
The LTC4002 can be shut down by pulling the COMP pin
to ground which pulls the GATE pin high turning off the
external P-channel MOSFET. When the COMP pin is re-
leased, the internal timer is reset and a new charge cycle
starts. In shutdown, the output of the CHRG pin is high
impedance and the quiescent current remains at 3mA.
Removing the input power supply will put the charger
into sleep mode. If the voltage at the VCC pin drops below
(VBAT + 250mV) or below the UVLO level, the LTC4002
goes into a low current (ICC= 10µA) sleep mode, reducing
the battery drain current.
CHRG Status Output Pin
When a charge cycle starts, the CHRG pin is pulled to
ground by an internal N-channel MOSFET which is capable
of driving an LED. When the charge current drops below
the End-of-Charge threshold for more than 120µs, the
N-channel MOSFET turns off and a weak 25µA current
source to ground is connected to the CHRG pin. This weak
25µA pull-down remains until the timer ends the charge
cycle, or the charger is in manual shutdown or sleep mode.
After a time out occurs (charge cycle ends), the pin will
become high impedance. By using two different value re-
sistors, a microprocessor can detect three states from this
pin (charging, end-of-charge and charging stopped) see
Figure 1.
VCC VDD
LTC4002
CHRG
390k
2k
µPROCESSOR
OUT
IN
4002 F02
Figure 1. Microprocessor Interface
To detect the charge mode, force the digital output pin,
OUT, high and measure the voltage at the CHRG pin. The
N-channel MOSFET will pull the pin low even with a 2k
pull-up resistor. Once the charge current drops below the
End-of-Charge threshold, the N-channel MOSFET is turned
off and a 25µA current source is connected to the CHRG
pin. The IN pin will then be pulled high by the 2k resistor
connected to OUT. Now force the OUT pin into a high
4002f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4002.PDF ] | |
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