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PDF LTC4064EMSE Data sheet ( Hoja de datos )
| Número de pieza | LTC4064EMSE | |
| Descripción | Monolithic Linear Charger for Back-Up Li-Ion Batteries | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC4064EMSE (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
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LTC4064
Monolithic Linear Charger
for Back-Up Li-Ion Batteries
FEATURES
s Preset 4V Charge Voltage with 1% Accuracy
Prolongs 4.2V Li-Ion Battery Lifetime
s Automatic Recharge
s Thermal Regulation Maximizes Charging Rate
without Risk of Overheating*
s No MOSFET, Sense Resistor or Blocking Diode
Required
s Programmable Charge Termination Timer
s Thermistor Input for Temperature Qualified Charging
s Programmable Charge Current with 7% Accuracy
s C/10 Charge Current Detection Output
s 25µA Supply Current in Shutdown Mode
s Charge Current Monitor Useful for Gas Gauging*
s Charges Directly from USB Port
s Tiny Thermally Enhanced 10-pin MSOP Package
U
APPLICATIO S
s File Servers, RAID Systems
s Storage Products
s Li-Ion Battery Back-Up
DESCRIPTIO
The LTC4064 is a standalone linear charger optimized for
prolonging the life of 1-cell Li-ion batteries in battery back-
up applications. By charging to a float voltage of 4V
instead of 4.2V or 4.1V, the LTC4064 decelerates the aging
process and capacity degradation when the battery is
unused for long periods of time but must be in a ready
state.
An external capacitor programs a safety timer to terminate
the charge cycle while the charge current is set externally
with a single resistor. When the input supply is removed,
the LTC4064 automatically enters a low current sleep
mode, dropping the battery drain current to less than 3µA.
Additional safety features designed to maximize battery
lifetime and reliability include NTC temperature sensing
and low battery charge conditioning (trickle charging).
The IC contains an on-chip power MOSFET and eliminates
the need for an external sense resistor and blocking diode.
The LTC4064 also includes C/10 detection circuitry, AC
present logic, and fault detection circuitry.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*US Patent No. 6522118
TYPICAL APPLICATIO
Standalone Back-Up Li-Ion Battery Charger
VIN = 5V
82
SHDN VCC
4.7µF
BAT 9
LTC4064
4 TIMER PROG 7
GND NTC
0.1µF 5, 11 6
IBAT = 1A
VFLOAT = 4V
1-CELL
Li-Ion
1.5k BATTERY*
1%
4064TA01
*AN OUTPUT CAPACITOR MAY BE REQUIRED
DEPENDING ON BATTERY LEAD LENGTH
4064f
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LTC4064
PROG Pin Voltage
vs Charge Current
1.6
VCC = 5V
1.4 TA = 25°C
RPROG = 3k
1.2
1.0
0.8
0.6
0.4
0.2
0
0 50 100 150 200 250 300 350 400 450 500
CHARGE CURRENT (mA)
4064 G10
PROG Pin Voltage vs VCC
Constant Current Mode
1.515
1.510
VBAT = 3.5V
TA = 25°C
RPROG = 3k
1.505
1.500
1.495
1.490
1.485
4 4.5 5 5.5 6
VCC (V)
6.5 7
4064 G11
PROG Pin Voltage vs Temperature
Constant Current Mode
1.515
1.510
VCC = 5V
VBAT = 4V
RPROG = 3k
1.505
1.500
1.495
1.490
1.485
–50 –25 0
25 50
TEMPERATURE (°C)
75 100
4064 G12
Trickle Charge Current
vs Temperature
12
VBAT = 2V
TA = 25°C
11 RPROG = 3k
10
9
8
7
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4064 G13
CHRG Pin Weak Pull-Down
Current vs Temperature
35
VCC = 5V
34 IBAT < C/10
33
32
31
30
29
28
27
26
25
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
4064 G14
CHRG Pin Output Low Voltage
vs Temperature
0.6
VCC = 5V
ICHRG = 5mA
0.5
0.4
0.3
0.2
0.1
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4064 G15
Timer Error vs Temperature
5
VCC = 5V
4 CTIMER = 0.1µF
3
2
1
0
–1
–2
–3
–4
–5
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4064 G16
Timer Error vs VCC
5
TA = 25°C
4 CTIMER = 0.1µF
3
2
1
0
–1
–2
–3
–4
–5
4 4.5 5 5.5
VCC (V)
6
6.5 7
4064 G17
4064f
5
5 Page 
LTC4064
APPLICATIO S I FOR ATIO
V+ VDD
8
VCC
LTC4064
3
CHRG
400k
2k
µPROCESSOR
OUT
IN
4064 F03
Figure 3. Microprocessor Interface
VCC
RHOT
1%
RNTC
10k
NTC
7/8 VCC
1/2 VCC
–
+
+
–
TOO COLD
TOO HOT
full-scale current (C/10), 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 pull-up.
By forcing the OUT pin to a high impedance state, the
current source will pull the pin low through the 400k
resistor. When the internal timer has expired, the CHRG
pin will assume a high impedance state and the 400k
resistor will then pull the pin high to indicate that charging
has terminated.
NTC Thermistor
The battery temperature is measured by placing a negative
temperature coefficient (NTC) thermistor close to the
battery pack. The NTC circuitry is shown in Figure 4. To use
this feature, connect a 10k NTC thermistor between the
NTC pin and ground and a resistor (RHOT) from the NTC pin
to VCC. RHOT should be a 1% resistor with a value equal to
the value of the chosen NTC thermistor at 50°C (this value
is 4.1k for a Vishay NTHS0603N02N1002J thermistor).
The LTC4064 goes into hold mode when the resistance of
the NTC thermistor drops below 4.1k which should be
approximately 50°C. The hold mode freezes the timer and
stops the charge cycle until the thermistor indicates a
return to a valid temperature. As the temperature drops,
the resistance of the NTC thermistor rises. The LTC4064
is designed to go into hold mode when the value of the NTC
thermistor increases to seven times the value of RHOT. For
a Vishay NTHS0603N02N1002J thermistor, this value is
28.7k which corresponds to approximately 0°C. The hot
and cold comparators each have approximately 2°C of
hysteresis to prevent oscillation about the trip point. The
NTC function can be disabled by grounding the NTC pin.
3/160 VCC
+
LTC4064
–
Figure 4
DISABLE NTC
4064 F04
Thermistors
The LTC4064 NTC trip points were designed to work with
thermistors whose resistance-temperature characteris-
tics follow Vishay Dale’s “R-T Curve 2”. The Vishay
NTHS0603N02N1002J is an example of such a ther-
mistor. However, Vishay Dale has many thermistor prod-
ucts that follow the “R-T Curve 2” characteristic in a variety
of sizes. Futhermore, any thermistor whose ratio of RCOLD
to RHOT is about 7.0 will also work (Vishay Dale R-T Curve
2 shows a ratio of RCOLD to RHOT of 2.816/0.4086 = 6.9).
NTC Layout Considerations
It is important that the NTC thermistor not be in close
thermal contact with the LTC4064. Because the LTC4064
package can reach temperatures in excess of the 50°C trip
point, the NTC function can cause a hysteretic oscillation
which turns the charge current on and off according to the
package temperature rather than the battery temperature.
This problem can be eliminated by thermally coupling the
NTC thermistor to the battery and not to the LTC4064.
Furthermore, it is essential that the VCC connection to
RHOT is made according to standard Kelvin sense tech-
niques. Since VCC is a high current path into the LTC4064,
it is essential to minimize voltage drops between the VCC
input pin and the top of RHOT.
4064f
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4064EMSE.PDF ] | |
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