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PDF LTC4065A Data sheet ( Hoja de datos )
| Número de pieza | LTC4065A | |
| Descripción | Standalone 750mA Li-Ion Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC4065/LTC4065A
Standalone 750mA Li-Ion
Battery Charger in 2 × 2 DFN
FEATURES
■ Complete Linear Charger in 2mm × 2mm DFN
Package
■ C/10 Charge Current Detection Output
■ Timer Termination
■ Charge Current Programmable up to 750mA with
5% Accuracy
■ No External MOSFET, Sense Resistor or Blocking
Diode Required
■ Preset 4.2V Float Voltage with 0.6% Accuracy
■ Constant-Current/Constant-Voltage Operation with
Thermal Feedback to Maximize Charging Rate
Without Risk of Overheating
■ ACPR Pin Indicates Presence of Input Supply
(LTC4065A Only)
■ Charge Current Monitor Output for Gas Gauging
■ Automatic Recharge
■ Charges Single Cell Li-Ion Batteries Directly from
USB Port
■ 20µA Supply Current in Shutdown Mode
■ Soft-Start Limits Inrush Current
■ Tiny 6-Lead (2mm × 2mm) DFN Package
U
APPLICATIO S
■ Wireless PDAs
■ Cellular Phones
■ Portable Electronics
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
DESCRIPTIO
The LTC®4065 is a complete constant-current/constant-
voltage linear charger for single-cell lithium-ion batteries.
Its 2mm × 2mm DFN package and low external component
count make the LTC4065 especially well-suited for por-
table applications. Furthermore, LTC4065 is specifically
designed to work within USB power specifications.
The CHRG pin indicates when charge current has dropped
to ten percent of its programmed value (C/10). An internal
timer terminates charging according to battery manufac-
turer specifications.
No external sense resistor or blocking diode is required
due to the internal MOSFET architecture. Thermal feed-
back regulates charge current to limit the die temperature
during high power operation or high ambient temperature
conditions.
When the input supply (wall adapter or USB supply) is
removed, the LTC4065 automatically enters a low current
state, dropping battery drain current to less than 1µA. With
power applied, LTC4065 can be put into shutdown mode,
reducing the supply current to less than 20µA.
The full-featured LTC4065 also includes automatic re-
charge, low-battery charge conditioning (trickle charg-
ing), soft-start (to limit inrush current) and an open-drain
status pin to indicate the presence of an adequate input
voltage (LTC4065A only).
The LTC4065 is available in a tiny 6-lead, low profile
(0.75mm) 2mm × 2mm DFN package.
TYPICAL APPLICATIO
Standalone Li-Ion Battery Charger
VIN
4.3V TO 5.5V
C1
1µF
R2*
1Ω
R1
510Ω
VCC BAT
LTC4065
CHRG PROG
EN GND
500mA
+ 4.2V
Li-Ion
R3 BATTERY
2k
4065 TA01
*SERIES 1Ω RESISTOR ONLY NEEDED FOR INDUCTIVE INPUT SUPPLIES
4065f
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1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LTC4065/LTC4065A
Undervoltage Lockout Threshold
Voltage vs Temperature
4.0
3.8
RISE
3.5
3.3
FALL
3.0
2.8
Manual Shutdown Threshold
Voltage vs Temperature (LTC4065)
1.0
0.9
RISE
0.8
FALL
0.7
0.6
Manual Shutdown Supply Current
vs Temperature
40
VCC = 5V
VEN = 5V
30
20
10
2.5
–50 –25
0
25 50
TEMPERATURE (°C)
75 100
4065 G16
0.5
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4065 G11
0
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4065 G12
EN Pin Current (LTC4065)
4.0
VCC = 5V
3.5 TA = 25°C
3.0
2.5
2.0
Trickle Charge Current
vs Supply Voltage
60
VBAT = 2V
TA = 25°C
50
RPROG = 2k
40
30
Trickle Charge Current
vs Temperature
60
VCC = 5V
VBAT = 2V
50
RPROG = 2k
40
30
1.5
1.0
0.5
0
2 2.5 3 3.5 4 4.5 5
VEN (V)
4065 G13
20
10
0
4
RPROG = 10k
4.5 5 5.5
SUPPLY VOLTAGE (V)
6
4065 G14
20
RPROG = 10k
10
0
–50 –25
0
25 50 75
TEMPERATURE (°C)
100
4065 G15
CHRG Pin Output Low Voltage
vs Temperature
140
VCC = 5V
120 ICHRG = 5mA
ACPR Pin Output Low Voltage vs
Temperature (LTC4065A Only)
140
VCC = 5V
120 IACPR = 5mA
100 100
80 80
60 60
40 40
20 20
0
–50 –25
0
25 50 75
TEMPERATURE (°C)
100
4065 G10
0
–50 –25
0
25 50 75 100
TEMPERATURE (°C)
4065 G17
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OPERATIO
Once the charge cycle terminates, the LTC4065 continu-
ously monitors the BAT pin voltage using a comparator
with a 2ms filter time. When the average battery voltage
falls below 4.1V (which corresponds to 80% to 90%
battery capacity), a new charge cycle is initiated and a 2.25
hour timer begins. This ensures that the battery is kept at,
or near, a fully charged condition and eliminates the need
for periodic charge cycle initiations. The CHRG output
assumes a strong pull-down state during recharge cycles
until C/10 is reached when it transitions to a high
impendance state.
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage is
low (below 2.9V), the charger goes into trickle charge,
reducing the charge current to 10% of the full-scale
current. If the low-battery voltage persists for one quarter
of the total time (1.125 hour), the battery is assumed to be
defective, the charge cycle is terminated and the CHRG pin
output pulses at a frequency of 2Hz with a 80% duty cycle.
If for any reason the battery voltage rises above 2.9V, the
charge cycle will be restarted. To restart the charge cycle
(i.e., when the defective battery is replaced with a dis-
charged battery), simply remove the input voltage and
reapply it, temporarily pull the EN pin above the shutdown
threshold (LTC4065), or momentarily float the PROG pin
and reconnect it (LTC4065A).
CHRG Status Output Pin
The charge status indicator pin has three states: pull-
down, pulse at 2Hz (see Trickle Charge and Defective
Battery Detection) and high impedance. The pull-down
state indicates that the LTC4065 is in a charge cycle. A high
impedance state indicates that the charge current has
dropped below 10% of the full-scale current or the LTC4065
is disabled. Figure 2 shows the CHRG status under various
conditions.
Power Supply Status Indicator
(ACPR, LTC4065A Only)
The power supply status output has two states: pull-down
and high impedance. The pull-down state indicates that
VCC is above the undervoltage lockout threshold (see
Undervoltage Lockout). When this condition is not met,
LTC4065/LTC4065A
the ACPR pin is high impedance indicating that the
LTC4065A is unable to charge the battery.
Charge Current Soft-Start and Soft-Stop
The LTC4065 includes a soft-start circuit to minimize the
inrush current at the start of a charge cycle. When a charge
cycle is initiated, the charge current ramps from zero to the
full-scale current over a period of approximately 180µs.
Likewise, internal circuitry slowly ramps the charge cur-
rent from full-scale to zero when the charger is shut off or
self terminates. This has the effect of minimizing the
transient current load on the power supply during start-up
and charge termination.
Constant-Current/Constant-Voltage/
Constant-Temperature
The LTC4065/LTC4065A use a unique architecture to
charge a battery in a constant-current, constant-voltage
and constant-temperature fashion. Figures 1a and 1b
show simplified block diagrams of the LTC4065 and
LTC4065A, respectively. Three of the amplifier feedback
loops shown control the constant-current, CA, constant-
voltage, VA, and constant-temperature, TA modes. A
fourth amplifier feedback loop, MA, is used to increase the
output impedance of the current source pair; M1 and M2
(note that M1 is the internal P-channel power MOSFET). It
ensures that the drain current of M1 is exactly 1000 times
greater than the drain current of M2.
Amplifiers CA and VA are used in separate feedback loops
to force the charger into constant-current or constant-
voltage mode, respectively. Diodes D1 and D2 provide
priority to either the constant-current or constant-voltage
loop; whichever is trying to reduce the charge current the
most. The output of the other amplifier saturates low
which effectively removes its loop from the system. When
in constant-current mode, CA servos the voltage at the
PROG pin to be precisely 1V. VA servos its inverting input
to an internal reference voltage when in constant-voltage
mode and the internal resistor divider, made up of R1 and
R2, ensures that the battery voltage is maintained at 4.2V.
The PROG pin voltage gives an indication of the charge
current during constant-voltage mode as discussed in
“Programming Charge Current”.
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11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4065A.PDF ] | |
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