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PDF LTC4001-1 Data sheet ( Hoja de datos )
| Número de pieza | LTC4001-1 | |
| Descripción | 2A Synchronous Buck Li-Ion Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
n Low Power Dissipation
n 2A Maximum Charge Current
n No External MOSFETs, Sense Resistor or
Blocking Diode Required
n Remote Sensing at Battery Terminals
n Programmable Charge Termination Timer
n Preset 4.1V Float Voltage with ±0.5% Accuracy
wwwn.Da4t.a1SVheFelot4aUt.cVoomltage Improves Battery Life and High
Temperature Safety Margin
n Programmable Charge Current Detection/
Termination
n Automatic Recharge
n Thermistor Input for Temperature Qualified
Charging
n Compatible with Current Limited Wall Adapters
n Low Profile 16-Lead (4mm × 4mm) QFN Package
APPLICATIONS
n Handheld Battery-Powered Devices
n Handheld Computers
n Charging Docks and Cradles
n Digital Cameras
n Smart Phones
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
LTC4001-1
2A Synchronous
Buck Li-Ion Charger
DESCRIPTION
The LTC®4001-1 is a 2A Li-Ion battery charger intended for
5V wall adapters. It utilizes a 1.5MHz synchronous buck
converter topology to reduce power dissipation during
charging. Low power dissipation, an internal MOSFET and
sense resistor allow a physically small charger that can be
embedded in a wide range of handheld applications. The
LTC4001-1 includes complete charge termination circuitry,
automatic recharge and a ±1% 4.1V float voltage. Input
short-circuit protection is included so no blocking diode
is required.
This 4.1V version of the standard LTC4001 is intended
for applications which will be operated or stored above
approximately 60°C. Under these conditions, the reduced
float voltage will trade-off initial cell capacity for the benefit
of increased capacity retention over the life of the battery. A
reduced float voltage also minimizes swelling in prismatic
and polymer cells, and avoids open CID (pressure fuse)
in cylindrical cells.
Battery charge current, charge timeout and end-of-charge
indication parameters are set with external components.
Additional features include shorted cell detection, tempera-
ture qualified charging and overvoltage protection. The
LTC4001-1 is available in a low profile (0.75mm) 16-lead
(4mm × 4mm) QFN package.
TYPICAL APPLICATION
2A Single Cell Li-Ion Battery Charger
1.5μH
VIN
4.5V TO 5.5V
10μF
VINSENSE
PVIN
SW
SENSE
BATSENS
BAT
PGND
CHRG
LTC4001-1
NTC
FAULT
EN
PROG IDET TIMER
SS GNDSENS
274Ω
0.22μF
0.1μF
10μF + 4.1V
Li-Ion
40011 TA01a
Power Loss vs VBAT
Charging (PWM Mode)
1.25
1.00
0.75
0.50
0.25
VIN = 5V
2A CHARGER
0
3 3.25
3.5
3.75
VBAT (V)
4 4.25
40011 TA01b
40011fa
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC4001-1
Soft-Start (PWM Mode)
INPUT
CURRENT (IIN)
0.5A/DIV
0
INDUCTOR
CURRENT (IL)
0.5A/DIV
SOFT-START
0
VOLTAGE (VSS)
1V/DIV 0
EN PIN (VEN)
www.Data5SVh/DeIeVt40U.com
VBAT = 3.5V
VIN = 5V
2ms/DIV
40011 G09
IDET Threshold vs RIDET for
RPROG = 549Ω
400
CHRG Pin Temperature Fault
Behavior (Detail)
350
300
250 CHRG
1V/DIV
200
150
100
50
TIME (20μs/DIV)
40011 G11
0
300 400 500 600 700 800 900 100011001200
RIDET (Ω)
40011 G10
PIN FUNCTIONS
BAT (Pin 1): Battery Charger Output Terminal. Connect a
10μF ceramic chip capacitor between BAT and PGND to
keep the ripple voltage small.
SENSE (Pin 2): Internal Sense Resistor. Connect to ex-
ternal inductor.
PGND (Pin 3): Power Ground.
GNDSENS (Pin 4): Ground Sense. Connect this pin to the
negative battery terminal. GNDSENS provides a Kelvin
connection for PGND and must be connected to PGND
schematically.
SW (Pin 5): Switch Node Connection. This pin connects
to the drains of the internal main and synchronous power
MOSFET switches. Connect to external inductor.
EN (Pin 6): Enable Input Pin. Pulling the EN pin high
places the LTC4001-1 into a low power state where the
BAT drain current drops to less than 3μA and the supply
current is reduced to less than 50μA. For normal opera-
tion, pull the pin low.
CHRG (Pin 7): Open-Drain Charge Status Output. When the
battery is being charged, CHRG is pulled low by an internal
N-channel MOSFET. When the charge current drops below
the IDET threshold (set by the RIDET programming resistor)
for more than 5milliseconds, the N-channel MOSFET turns
off and a 30μA current source is connected from CHRG to
ground. (This signal is latched and is reset by initiating a
new charge cycle.) When the timer runs out or the input
supply is removed, the current source will be disconnected
and the CHRG pin is forced to a high impedance state. A
temperature fault causes this pin to blink.
PVIN (Pin 8): Positive Supply Voltage Input. This pin con-
nects to the power devices inside the chip. VIN ranges
from 4V to 5.5V for normal operation. Operation down to
the undervoltage lockout threshold is allowed with cur-
rent limited wall adapters. Decouple with a 10μF or larger
surface mounted ceramic capacitor.
VINSENSE (Pin 9): Positive Supply Sense Input. This pin
connects to the inputs of all input comparators (UVL, VIN
to VBAT). It also supplies power to the controller portion
of this chip. When the BATSENS pin rises to within 30mV
of VINSENSE, the LTC4001-1 enters sleep mode, dropping
IIN to 50μA. Tie this pin directly to the terminal of the PVIN
decoupling capacitor.
FAULT (Pin 10): Battery Fault. This pin is a logic high if
a shorted battery is detected or if a temperature fault is
detected. A temperature fault occurs with the temperature
monitor circuit enabled and the thermistor temperature is
either below 0°C or above 50°C (typical).
40011fa
5
5 Page 
LTC4001-1
APPLICATIONS INFORMATION
The equations for calculating R1 (used in single resistor
programming) differ from the equations for calculating
RPROG and RIDET (2-resistor programming) and reflect
the fact that the current from both the IDET and PROG
pins must flow through a single resistor R1 when a single
programming resistor is used.
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
wwwo.Df adtraivSihnegeta4nU.LcoEmD. When the charge current drops below
the end-of-charge (IDET) threshold for at least 4ms,
and the battery voltage is close to the float voltage, the
N-channel MOSFET turns off and a weak 30μA current
source to ground is connected to the CHRG pin. This
weak pull-down remains until the charge cycle ends. After
charging ends, the pin will become high impedance. By
using two different value resistors, a microprocessor can
detect three states from this pin (charging, end-of-charge
and charging stopped). See Figure 2.
To detect the charge mode, force the digital output pin,
OUT, high and measure the voltage on 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 30μA 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 impedance state, the current source will pull the
pin low through the 390k resistor. When charging stops,
the CHRG pin changes to a high impedance state and the
390k resistor will then pull the pin high to indicate charg-
ing has stopped.
Charge Termination
Battery charging may be terminated several different ways,
depending on the connections made to the TIMER pin. For
time-based termination, connect a capacitor between the
TIMER pin and GNDSENS (CTIMER = Time(Hrs) 0.0733μF).
Charging may be terminated when charge current drops
below the IDET threshold by tying TIMER to GNDSENS.
Finally, charge termination may be defeated by tying TIMER
to IDET. In this case, an external device can terminate
charging by pulling the EN pin high.
Battery Temperature Detection
When battery temperature is out of range (either too hot
or too cold) charging is temporarily halted and the FAULT
pin is driven high. In addition, if the battery is still charg-
ing at a high rate (greater than the IDET current) when a
temperature fault occurs, the CHRG pin NMOS turns on
and off at approximately 50kHz, alternating between a
high and low duty factor at an approximate rate of 1.5Hz
(Figure 3). This provides a low rate visual indication (1.5Hz)
when driving an LED from the CHRG pin while providing
a fast temperature fault indication (20μs typical) to a mi-
croprocessor by tying the CHRG pin to an interrupt line.
Serrations within this pulse are typically 500ns wide.
VIN
LTC4001-1
CHRG
VDD
R1
390k R2
2k
μPROCESSOR
OUT
IN
40011 F02
Figure 2. Microprocessor Interface
667ms
20μs
40011 F03
Figure 3. CHRG Temperature Fault Waveform
40011fa
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC4001-1.PDF ] | |
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