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PDF LTC4056-4.2 Data sheet ( Hoja de datos )
| Número de pieza | LTC4056-4.2 | |
| Descripción | Linear Li-Ion Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC4056-4.2
Linear Li-Ion Charger
with Termination in ThinSOT
FEATURES
s Standalone Li-Ion Charger with Termination
s Programmable Termination Timer
s No Sense Resistor or Blocking Diode Required
s Suitable for USB-Powered Charging
s Undervoltage Charge Current Limiting
s Preset Charge Voltage with ±0.6% Accuracy
s Programmable Charge Current: 200mA to 700mA
s Automatic Recharge with Shortened Charge Cycle
s Self-Protection for Overcurrent/Overtemperature
s 40µA Supply Current in Shutdown Mode
s Negligible Battery Drain Current in Shutdown
s Low Battery Charge Conditioning (Trickle Charging)
s CHRG Status Output including AC Present
s PCB Total Solution Area only 75mm2 (700mA)
s Low Profile (1mm) SOT-23 Package
U
APPLICATIO S
s Cellular Telephones
s Handheld Computers
s Digital Cameras
s Charging Docks and Cradles
s Low Cost and Small Size Chargers
DESCRIPTIO
The LTC®4056 is a low cost, single-cell, constant-current/
constant-voltage Li-Ion battery charger controller with a
programmable termination timer. When combined with a
few external components, the LTC4056 forms a very small
standalone charger for single cell lithium-ion batteries.
Charge current and charge time are set externally with a
single resistor and capacitor, respectively. The LTC4056
charges to a final float voltage accurate to ±0.6%. Manual
shutdown is accomplished by grounding the TIMER/
SHDN pin, while removing input power automatically puts
the LTC4056 into a sleep mode. Both the shutdown and
sleep modes drain near zero current from the battery; the
shutdown mode reduces supply current to 40µA.
The output driver is both current limited and thermally
protected to prevent operating outside of safe limits. No
external blocking diode or sense resistor is required. The
LTC4056 also includes low battery charge conditioning
(trickle charging), undervoltage charge current limiting,
automatic recharge and a charge status output.
The LTC4056 is available in a low profile (1mm) 8-lead
SOT-23 (ThinSOTTM) package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
4.5V TO 6.5V
LTC4056
VCC ISENSE
700mA
CHARGE
CHRG
DRIVE
ZXT1M322
STATUS
TIMER/SHDN BAT
1µF
PROG
1µF 1.3k GND
+ 1-CELL
4.2V Li-Ion
4056-4.2 TA01
VIN Undervoltage Charge
Current Limiting
800
VBAT = 4V
700 RPROG = 1.3k
ICHG = 700mA
600 INPUT Z = 100mΩ
CONSTANT
CURRENT
500 UNDERVOLTAGE CHARGE
CURRENT LIMITING
400
300
200
UNDERVOLTAGE
100
LOCKOUT
AT 4.35V
0
4.40 4.45 4.50 4.55 4.60 4.65 4.70 4.75
VIN (V)
4056 TA02
405642f
1
1 page  
LTC4056-4.2
PI FU CTIO S
VCC (Pin 1): Positive Input Supply Voltage. This pin
supplies power to the internal control circuitry and exter-
nal PNP transistor through the internal current sense
resistor. This pin should be bypassed to ground with a
capacitor in the range of 1µF to 10µF.
ISENSE (Pin 2): Sense Node for Charge Current. Current
from VCC passes through the internal current sense resis-
tor and out of the ISENSEpin to supply current to the emitter
of the external PNP transistor. The collector of the PNP
provides charge current to the battery.
DRIVE (Pin 3): Base Drive Output for the External PNP
Pass Transistor. Provides a controlled sink current to
drive the base of the PNP. This pin has current limiting
protection.
GND (Pin 4): Ground. Provides a reference for the internal
voltage regulator and a return for all internal circuits.
When in the constant voltage mode, the LTC4056 will
precisely regulate the voltage between the BAT and GND
pins. The battery ground should connect close to the GND
pin to avoid voltage drop errors.
PROG (Pin 5): Charge Current Programming Pin. Pro-
vides a virtual reference voltage of 1V for an external
resistor (RPROG) connected between this pin and ground
to program the battery charge current. In constant current
mode the typical charge current is 915 times the current
through this resistor (ICHG = 915V/RPROG). Current is
limited to approximately 1.4mA (ICHG of approximately
1.4A).
BAT (Pin 6): Battery Voltage Sense Input. A precision
internal resistor divider sets the final float voltage on this
pin. This divider is disconnected in the manual shutdown
or sleep mode. No bypass capacitance is needed on this
pin for stable operation when a battery is present. How-
ever, any low ESR capacitor exceeding 22µF on this pin
should be decoupled with 0.2Ω to 1Ω resistor. Without a
battery, a minimum bypass capacitance of 4.7µF with
0.5Ω series resistance is required.
TIMER/SHDN (Pin 7): Programmable Charge Termination
Timer and Shutdown Input. Pulling this pin below the
shutdown threshold voltage will shut down the charger
reducing the supply current to approximately 40µA and
the battery drain current to near 0µA. A capacitor on this
pin programs the charge termination timer.
CHRG (Pin 8): Open-Drain Charge Status Output. When
the battery is being charged, the CHRG pin is pulled low by
an internal N-channel MOSFET. When the timer has timed
out (terminating the charge cycle) or when the LTC4056 is
in shutdown, but power is applied to the IC (i.e., VCC >
VUVLOI), a 12µA current source is connected from the
CHRG pin to ground. The CHRG pin is forced to a high
impedance state when input power is not present (i.e., VCC
< VUVLOD).
405642f
5
5 Page 
LTC4056-4.2
APPLICATIO S I FOR ATIO
DRIVE pin could be pulled from the battery through the
forward biased collector base junction.
For example, to program a charge current of 500mA with
a minimum supply voltage of 4.75V, the minimum operat-
ing VCE is:
VCE(MIN)(V) = 4.75 – (0.5) • (0.2) – 4.2 = 0.45V
Another important factor to consider when choosing the
PNP pass transistor is the power handling capability. The
transistor data sheet will usually give the maximum rated
power dissipation at a given ambient temperature with a
power derating for elevated temperature operation. The
maximum power dissipation of the PNP when charging is:
PD(MAX)(W) = IBAT • (VCC(MAX) – VBAT(MIN))
VCC(MAX) is the maximum supply voltage and VBAT(MIN) is
the minimum battery voltage when discharged.
Once the maximum power dissipation and VCE(MIN) are
known, Table 1 can be used as a guide in selecting some
PNPs to consider. In the table, very low VCESAT is less than
0.25V, low VCESAT is 0.25V to 0.5V and the others are 0.5V
to 0.8V all depending on the current. See the manufac-
turer data sheet for details. All of the transistors are rated
to carry at least 1A continuously as long as the power
dissipation is within limits. In addition, the maximum
supply voltage, minimum battery voltage and chosen
charge current should be checked against the
manufacturer’s data sheet to ensure that the PNP transis-
tor is operating within its safe operating area. The Stabil-
ity section addresses caution in the use of very high beta
PNP transistors.
Should overheating of the PNP transistor be a concern,
protection can be achieved with a positive temperature
coefficient (PTC) thermistor wired in series with the
current programming resistor and thermally coupled to
the transistor. The PTH9C chip series from Murata has a
steep resistance increase at temperature thresholds from
85°C to 145°C making it behave somewhat like a thermo-
stat switch. For example, the model PTH9C16TBA471Q
thermistor is 470Ω at 25°C but abruptly increases its
resistance to 4.7k at 125°C. Below 125°C, the device
exhibits a small negative TC. The 470Ω thermistor can be
added in series with a 976Ω resistor to form the current
programming resistor for a 640mA charger. Should the
thermistor reach 125°C, the charge current will drop to
160mA and inhibit any further increase in temperature.
Stability
The LTC4056 contains two control loops: constant volt-
age and constant current. The constant voltage loop is
stable without any compensation when a battery is con-
nected with low impedance leads. Excessive lead length,
Table 1. PNP Pass Transistor Selection Guide
MAXIMUM PD(W)
MOUNTED ON BOARD
AT TA = 25°C
3
PACKAGE STYLE
2 x 2MLP
ZETEX PART NUMBER
ZXT1M322
0.5
SOT-23
FMMT549
0.625
SOT-23
FMMT720
1
SOT-89
FCX589 or BCX69
1.1
SOT-23-6
ZXT13P12DE6
1 to 2
SOT-89
FCX717
2
SOT-223
FZT589
2
SOT-223
BCP69 or FZT549
0.75 FTR
1 ATV
2 SOT-89
10 (TC = 25°C)
TO-252
ROHM PART NUMBER COMMENTS
Very Low VCESAT
Low VCESAT
Very Low VCESAT, High Beta
Very Low VCESAT, High Beta, Small
Very Low VCESAT, High Beta
Low VCESAT
2SB822
2SB1443
2SA1797
2SB1182
Low VCESAT
Low VCESAT
Low VCESAT
Low VCESAT, High Beta
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4056-4.2.PDF ] | |
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