LT3651-8.2_15 Datasheet, PDF (1/24 Pages) Linear Technology – Monolithic 4A High Voltage 2-Cell Li-Ion Battery Charger

LT3651-8.2/LT3651-8.4
Monolithic 4A High Voltage
2-Cell Li-Ion Battery Charger
FEATURES
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.
DESCRIPTION
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
V_IN
12V TO 32V
Si7611DN
12V to 32V 2-Cell 4A Charger
100k _10V
10k
301k
CLP CLN V_IN
SHDN
SW
LT3651-8.2/LT3651-8.4
ACPR
BOOST
FAULT
CHRG
SENSE
RT
BAT
TIMER
NTC
I_LIM RNG/SS 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 V_IN
91
EFFICIENCY
5.0
V_BAT = 7.8V
I_BAT = 4A
90
4.5
89
4.0
88
87
10
POWER LOSS
15
20
25
V_IN (V)
3.5
3.0
30
35
36518284 TA01b
36518284fa
1