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PDF LT3651-8.4 Data sheet ( Hoja de datos )
| Número de pieza | LT3651-8.4 | |
| Descripción | Monolithic 4A High Voltage 2-Cell Li-Ion Battery Charger | |
| Fabricantes | Linear | |
| Logotipo |  |
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LT3651-8.2/LT3651-8.4
Monolithic 4A High Voltage
2-Cell Li-Ion Battery Charger
FEATURES
DESCRIPTION
n Wide Input Voltage Range: 9V to 32V
(40V Absolute Maximum)
n Programmable Charge Current Up to 4A
n Selectable C/10 or Onboard Timer Termination
n Dynamic Charge Rate Programming/Soft-Start
n Programmable Input Current Limit
n ±0.5% Float Voltage Accuracy
n ±7.5% Charge Current Accuracy
n ±4% 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 Average Current Mode, Synchronous Switcher
n User Programmable Frequency
n Low Profile (0.75mm) 5mm × 6mm 36-Lead
QFN Package
APPLICATIONS
n Industrial Handheld Instruments
n 12V to 24V Automotive and Heavy Equipment
n Desktop Cradle Chargers
n Notebook Computers
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.
The LT®3651-8.2/LT3651-8.4 are 2-cell, 4A Li-Ion/Poly-
mer battery chargers that operate over a 9V to 32V input
voltage range. An efficient monolithic average current
mode synchronous switching regulator provides constant
current, constant voltage charging with programmable
maximum charge current. A charging cycle starts with
battery insertion or when the battery voltage drops 2.5%
below the float voltage. Charger termination is selectable
as either charge current or internal safety timer timeout.
Charge current termination occurs when the charge cur-
rent falls to one-tenth the programmed maximum current
(C/10). Timer based termination is typically set to three
hours and is user programmable (charging continues
below C/10 until timeout). Once charging is terminated,
the LT3651-8.2/LT3651-8.4 supply current drops to 85µA
into a standby mode.
The LT3651-8.2/LT3651-8.4 offer several safety features.
A discharged battery is preconditioned with a small trickle
charge and generates a signal if unresponsive. A thermistor
monitors battery temperature, halting charging if out of
range. Excessive die temperature reduces charge current.
Charge current is also reduced to maintain constant input
current to prevent excessive input loading.
The LT3651-8.2/LT3651-8.4 are available in a 5mm ×
6mm 36-lead QFN package.
TYPICAL APPLICATION
VIN
12V TO 32V
Si7611DN
12V to 32V 2-Cell 4A Charger
100k 10V
10k
301k
CLP CLN
SHDN
VIN
SW
LT3651-8.2/LT3651-8.4
ACPR
BOOST
FAULT
CHRG
SENSE
RT
TIMER
ILIM RNG/SS
BAT
NTC
GND
TO
SYSTEM
22µF LOAD
1µF
CMPSH1-4
10µH
WÜRTH 74477010
24mΩ
100µF +
2-CELL
Li-Ion
BATTERY
365188284 TA01a
For more information www.linear.com/LT3651-8.2
Efficiency, Power Loss vs VIN
91
EFFICIENCY
VIBBAATT==47A.8V
5.0
90 4.5
89 4.0
88
87
10
POWER LOSS
15 20 25
VIN (V)
3.5
3.0
30 35
36518284 TA01b
36518284fa
1
1 page  
LT3651-8.2/LT3651-8.4
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Float Voltage
vs Temperature
1.0
0.5
0
–0.5
–1.0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
36518284 G01
C/10 Threshold
vs Temperature
(VSENSE
–
VBAT)
11
10
VIN Standby Mode Current
vs Temperature
100
95
90
85
80
75
70
65
60
55
50
–50 –25
0
25 50 75 100
TEMPERATURE (°C)
36518284 G02
Maximum Charge Current
vs
of
PVrRoNgGr/aSmS amsead
Percentage
IIN(MAX)
120
100
80
SENSE and BAT Pin Currents
vs BAT Voltage (VSENSE = VBAT)
150
LT3651-8.4
100
ISENSE
50 IBAT
0
–50
–100
–150
–200
–250
–300
–350
01 2 3 4 5 6 7 8 9
VBAT (V)
36518284 G03
I(CVHSGENCSuEr–reVnBt ALTi)mvist Temperature
101.0
100.5
9 60 100.0
40
8 99.5
20
7
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
0
0
36518284 G04
Charge Current vs VBAT as a
Percentage of Programmed
ICHG(MAX)
120
LT3651-8.4
100
0.2 0.4 0.6 0.8
VRNG/SS (V)
1.0 1.2
99.0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
36518284 G05
36518284 G06
Maximum Input Current
vs
of
PVrILoIgMraams ma ePderIcINe(nMtAaXg)e
120
100
80 80
60 60
40 40
20 20
0
56 7
89
VBAT (V)
36518284 G07
0
0 0.2 0.4 0.6 0.8 1.0 1.2
VILIM (V)
36518284 G08
For more information www.linear.com/LT3651-8.2
36518284fa
5
5 Page 
LT3651-8.2/LT3651-8.4
OPERATION
The ITH error voltage corresponds linearly to average cur-
rent sensed across the inductor current sense resistor.
Maximum charge current is controlled by clamping the
maximum voltage of ITH to 1V. This limits the maximum
current sense voltage (voltage across RSENSE) to 95mV
setting the maximum charge current. Manipulation of
maximum charge current is possible through the RNG/SS
and ILIM pins (see the RNG/SS: Dynamic Charge Current
Adjust, RNG/SS: Soft-Start and ILIM Control sections).
If the voltage on the BAT pin (VBAT) is below VBAT(PRE), A7
initiates the precondition mode. During the precondition
interval, the charger continues to operate in constant cur-
rent mode, but the ITH clamp is reduced to 0.15V reducing
charge current to 15% of the maximum programmed value.
As VBAT approaches the float voltage (VFLOAT) the voltage
error amp V-EA takes control of ITH and the charger transi-
tions into constant voltage (CV) mode. As this occurs, the
ITH voltage falls from the limit clamp and charge current is
reduced from the maximum value. When the ITH voltage
falls below 0.1V, A8 signals C/10. If the charger is config-
ured for C/10 termination the charge cycle is terminated.
Once the charge cycle is terminated, the CHRG status
pin becomes high impedance and the charger enters low
current standby mode.
The LT3651-8.2/LT3651-8.4 contain an internal charge
cycle timer that terminates a successful charge cycle af-
ter a programmed amount of time. This timer is typically
programmed to achieve end-of-cycle in three hours, but
can be configured for any amount of time by setting an
appropriate timing capacitor value (CTIMER). When timer
termination is used, the charge cycle does not terminate
after C/10 is achieved. Because the CHRG status pin re-
sponds to the C/10 current level, the IC will indicate a fully
charged battery status, but the charger will continue to
source low currents. At the programmed end of the cycle
time the charge cycle stops and the part enters standby
mode. If the battery did not achieve at least 97.5% of the
full float voltage at the end-of-cycle, charging is deemed
unsuccessful and another full-timer cycle is initiated.
Use of the timer function also enables bad battery detec-
tion. This fault condition is achieved if the battery does
not respond to preconditioning and the charger remains
in (or enters) precondition mode after one-eighth of the
programmed charge cycle time. A bad battery fault halts
the charging cycle, the CHRG status pin goes high imped-
ance and the FAULT pin is pulled low.
When the LT3651-8.2/LT3651-8.4 terminate a charging
cycle, whether through C/10 detection or by reaching
timer end-of-cycle, the average current mode analog loop
remains active but the internal float voltage reference is
reduced by 2.5%. Because the voltage on a successfully
charged battery is at the full float voltage, the voltage er-
ror amp detects an overvoltage condition and rails low.
When the voltage error amp output drops below 0.3V,
the IC enters standby mode, where most of the internal
circuitry is disabled and the VIN bias current is reduced
to <100µA. When the voltage on the BAT pin drops below
the reduced float reference level, the output of the voltage
error amp will climb, at which point the IC comes out of
standby mode and a new charging cycle is initiated.
The system current limit allows charge current to be
reduced in order to maintain a constant input current.
Input current is measured via a resistor (RCL) that is
placed between the CLP and CLN pins. Power is applied
through this resistor and is used to supply both VIN of the
chip and other system loads. An offset produced on the
inputs of A12 sets the threshold. When that threshold is
achieved, ITH is reduced, lowering the charge current thus
maintaining the maximum input current.
50µA of current is sourced from ILIM to a resistor (RILIM)
that is placed from that pin to ground. The voltage on ILIM
determines the regulating voltage across RCL. 1V on ILIM
corresponds to 95mV across RCL. The ILIM pin clamps
internally to 1V maximum.
If the junction temperature of the die becomes excessive,
A10 activates decreasing ITH and reduces charge current.
This reduces on-chip power dissipation to safe levels but
continues charging.
For more information www.linear.com/LT3651-8.2
36518284fa
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT3651-8.4.PDF ] | |
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