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PDF LT3650-4.2 Data sheet ( Hoja de datos )
| Número de pieza | LT3650-4.2 | |
| Descripción | (LT3650-4.1 / -4.2) High Voltage 2 Amp Monolithic Li-Ion Battery Charger | |
| Fabricantes | Linear Technology Corporation | |
| Logotipo |  |
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LT3650-4.1/LT3650-4.2
High Voltage 2 Amp
Monolithic Li-Ion Battery Charger
FEATURES
n Wide Input Voltage Range: 4.75V to 32V (40V
Absolute Maximum)
n Programmable Charge Current Up to 2A
n User-Selectable Termination: C/10 or Onboard
Termination Timer
n Dynamic Charge Rate Programming/Soft-Start Pin
n Programmable Input Current Limit
n No VIN Blocking Diode Required
n 1MHz Fixed Frequency
n Average Current Mode Control
n 0.5% Float Voltage Accuracy
n 5% Charge Current Accuracy
n 2.5% C/10 Detection Accuracy
n NTC Resistor Temperature Monitor
n Auto-Recharge at 97.5% Float Voltage
n Auto-Precondition at <70% Float Voltage
n Bad Battery Detection with Auto-Reset
n Binary Coded Open-Collector Status Pins
n 3mm × 3mm DFN-12 Package
APPLICATIONS
n Industrial Handheld Instruments
n 12V to 24V Automotive and Heavy Equipment
n Desktop Cradle Chargers
n Notebook Computers
DESCRIPTION
The LT®3650 is a complete monolithic single-cell Li-Ion/
Polymer battery charger that operates over a 4.75V to
32V input voltage range (7.5V minimum start-up voltage).
The LT3650 provides a constant-current/constant-volt-
age charge characteristic, with maximum charge current
externally programmable up to 2A, set using an external
current sense resistor. A precondition feature trickle-
charges a low voltage battery, and bad battery detection
provides a signal and suspends charging if a battery does
not respond to preconditioning.
The LT3650 can be configured to terminate charging when
charge current falls to C/10, or one-tenth the programmed
maximum current. Once charging is terminated, the LT3650
enters a low current (85μA) standby mode. An auto-restart
feature starts a new charging cycle if the battery voltage
drops 2.5% from the float voltage, or if a new battery is
inserted into a charging system.
The LT3650 contains a user-programmable internal safety
timer (typically set to a three hour full cycle time). The IC
can be configured to use this internal timer if a time-based
termination scheme is desired in which charging can con-
tinue below C/10 until a desired time is reached.
The LT3650 is available in a low profile (0.75mm) 3mm ×
3mm 12-pin DFN package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
7.5V to 32V Single-Cell Li-Ion 2A Charger
VIN
7.5V to 32V
10μF
VIN SW
CLP BOOST
SHDN
CHRG
LT3650-4.2
SENSE
FAULT
TIMER
BAT
NTC
RNG/SS
CMSH3-40MA
1μF
CMPSH1-4
6.8μH
0.05Ω
+
10μF
Li-ION
BATTERY
3650 TA01a
VBAT and Efficiency vs IBAT
100
VBAT
4.20
90
VIN = 12V
80 VIN = 20V
4.15
4.10
70
4.05
60
0
0.5 1 1.5 2
IBAT (A)
365042 TA01b
36504142f
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LT3650-4.1/LT3650-4.2
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
C/10 Threshold (VSENSE–VBAT)
vs Temperature
12
11
10
9
8
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
365042 G07
IMAX Current Limit (VSENSE–VBAT)
vs Temperature
101.0
VBAT = 3.5V
100.8
100.6
100.4
100.2
100.0
99.8
99.6
99.4
99.2
99.0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
365042 G09
CLP Input Limit Threshold (VCLP – VIN)
vs Temperature, ICHG at 50%
51.0
50.8
50.6
50.4
50.2
50.0
49.8
49.6
49.4
49.2
49.0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
365042 G08
Thermal Foldback – IMAX
Current Limit (VSENSE–VBAT) vs
Temperature
120
100
80
60
40
20
0
25 35 45 55 65 75 85 95 105 115 125 135
TEMPERATURE (°C)
365042 G10
CC/CV Charging; BAT Pin Bias
Current vs VBAT
2.2
2.0 LT3650-4.2
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
–0.2
–0.4
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
VBAT (V)
365042 G11
36504142f
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LT3650-4.1/LT3650-4.2
APPLICATIONS INFORMATION
VIN Input Supply
The LT3650 is biased directly from the charger input
supply through the VIN pin. This supply provides large
switched currents, so a high quality, low ESR decoupling
capacitor is recommended to minimize voltage glitches
on VIN. The VIN decoupling capacitor (CVIN) absorbs all
input switching ripple current in the charger, so it must
have an adequate ripple current rating. RMS ripple current
(ICVIN(RMS)) is:
1
ICVIN(RMS)
~
ICHG(MAX)
•
⎛
⎝⎜
VBAT
VIN
⎞
⎠⎟
•
⎛
⎝⎜
⎡
⎢
⎣
VIN
VBAT
⎤
⎥
⎦
−
⎞
1⎠⎟
2
which has a maximum at VIN = 2 • VBAT, where:
ICVIN(RMS) = ICHG(MAX)/2
The simple worst-case of 1/2 • ICHG(MAX) is commonly
used for design.
Bulk capacitance is a function of desired input ripple volt-
age (ΔVIN), and follows the relation:
CIN(BULK)
=
IMAX
•
⎛
⎝⎜
VBAT / VIN
ΔVIN
⎞
⎠⎟
(μF)
10μF is typically adequate for most charger applica-
tions.
BOOST Supply
The BOOST bootstrapped supply rail drives the internal
switch and facilitates saturation of switch transistor. Oper-
ating range of the BOOST pin is 0V to 4.5V, as referenced
to the SW pin. Connect a 1μF or greater capacitor from
the BOOST pin to the SW pin.
The voltage on the decoupling capacitor is refreshed
through a diode, with the anode connected to/from either
the battery output voltage or an external source, and the
cathode connected to the BOOST pin. Rate the diode av-
erage current greater than 0.1A, and its reverse voltages
greater than VIN(MAX).
VIN / BOOST Start-Up Requirement
The LT3650 operates with a VIN range of 4.75V to 32V,
however, a start-up voltage requirement exists due to
the nature of the nonsynchronous step-down switcher
topology used for the charger. If there is no BOOST supply
available, the internal switch requires (VIN – VSW) > 3V
to operate. This requirement does not exist if the BOOST
supply is available and (VBOOST – VSW) > 2V.
When an LT3650 charger is not switching, the SW pin is at
the same potential as the battery, which can be as high as
VBAT(FLT). For reliable start-up, the VIN supply must be at
least 3V above the SW pin. The minimum start-up speci-
fication of VIN at or above 7.5V provides ample margin to
satisfy this requirement. Once switching begins, the BOOST
supply capacitor gets charged such that (VBOOST – VSW)
> 2V, and the VIN requirement no longer applies.
In low VIN applications, the BOOST supply can be powered
by an external source for start-up, eliminating the VIN
start-up requirement.
VBAT Output Decoupling
An LT3650 charger output requires bypass capacitance
connected from the BAT pin to ground (CBAT). A 10μF ce-
ramic capacitor is required for all applications. In systems
where the battery can be disconnected from the charger
output, additional bypass capacitance may be desired for
visual indication of a no-battery condition (see the Status
Pins section).
If it is desired to operate a system load from the LT3650
charger output when the battery is disconnected, additional
bypass capacitance is required. In this type of application
with the charger being used as a DC/DC converter, exces-
sive ripple and/or low amplitude oscillations can occur
without additional output bulk capacitance. For these ap-
plications, place a 100μF low ESR nonceramic capacitor
(chip tantalum or organic semiconductor capacitors such
as Sanyo OS-CONs or POSCAPs) from BAT to ground,
in parallel with the 10μF ceramic bypass capacitor. This
additional bypass capacitance may also be required in
systems where the battery is connected to the charger
through long wires. The voltage rating on CBAT must meet
or exceed the battery float voltage.
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| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LT3650-4.2.PDF ] | |
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