LT3651-4.2 Datasheet, PDF (1/22 Pages) Linear Technology – Monolithic 4A High Voltage Li-Ion Battery Charger

FEATURES
n _{Wide Input Voltage Range: 4.8V 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 <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-Pin}
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 and
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property of their respective owners.
LT3651-4.2
Monolithic 4A High Voltage
Li-Ion Battery Charger
DESCRIPTION
The LT^®3651 is a 4A Li-Ion/Polymer battery charger that
operates over a 4.8V to 32V input voltage range. An ef-
ficient 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 current 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 supply
current drops to 85µA into a standby mode.
The LT3651 offers 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. Ex-
cessive die temperature reduces charge current. Charge
current is also reduced to maintain constant input current
to prevent excessive input loading.
The LT3651 is available in a 5mm × 6mm 36-pin QFN
package.
TYPICAL APPLICATION
7.5V to 32V Single Cell 4A Charger
V_IN
7.5V TO 32V
54.9k
CLP CLN V_IN
SHDN
SW
ACPR
FAULT
CHRG
BOOST
LT3651-4.2
SENSE
RT
TIMER
BAT
NTC
I_LIM RNG/SS GND
TO
SYSTEM
22µF ^LOAD
1µF
1N5819
3.3µH
24mΩ
+
100µF
BATTERY
365142 TA01a
V_BAT and Efficiency vs I_BAT
100
4.25
V_BAT
90
4.15
V_IN = 10V
80
4.05
V_IN = 20V
70
3.95
60
3.85
50
0
3.75
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
I_BAT (A)
365142 TA01b
365142fa
1