FEATURES
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LT3653
1.2A, HV Input Regulator
with Output Current Limit for
Battery Charger Applications
DESCRIPTION
The LT
®
3653 is a monolithic current mode PWM step-down
regulator with programmable output current limit. Typically,
it is used with battery charger power path controllers to
pre-regulate the output and optimize the battery charger
efficiency. Output current limit provides accurate control
over system power dissipation.
The wide operating input voltage range of 7.5V to 30V
suits the LT3653 to a variety of input sources, including
unregulated 12V wall adapters, 24V industrial supplies,
Firewire and automotive power. Input overvoltage protec-
tion allows the LT3653 to handle 60V input transients.
The LT3653 control pin, V
C
, is available for external battery
tracking control, Bat-Track. The LT3653 will block output
discharge during an open or shorted input.
The HVOK pin indicates that the internal bias supplies
are present and no faults have occurred (i.e., overtem-
perature and input overvoltage and undervoltage). The
LT3653 includes a 1.5MHz frequency oscillator, internal
compensation, and an internal boost diode to minimize the
number of external components. The LT3653 is available
in an 8-lead (2mm
×
3mm) package with exposed pads
for low thermal resistance.
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Wide Input Range:
– Operation from 7.5V to 30V
– Overvoltage Lockout Protects Circuit Through 60V
Transients
Operates with LTC Bat-Track™ Li-Ion Battery
Chargers to Maximize Efficiency
No Reverse Discharge Path from V
OUT
to V
IN
Programmable Output Current Limit
Integrated BOOST Diode
Thermal Protection
Small Application Size
Thermally Enhanced 2mm
×
3mm DFN Package
APPLICATIONS
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Battery Powered Equipment
Portable USB Devices – Cameras, MP3 Players,
PDAs
Automotive Battery Regulation
Multiple-Source Battery Chargers
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Bat-Track is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
High Voltage Single-Cell Battery Charger Application
V
IN
7.5V TO 30V
TRANSIENT
TO 60V
0.1μF
V
IN
4.7μF
LT3653
I
SENSE
I
LIM
27.4k
HVOK
GND
V
C
3653 TA01a
Efficiency vs Load Current
100
90
4.7μH
1.2A
SYSTEM
LOAD
EFFICIENCY (%)
80
70
60
50
40
0.1
V
IN
= 24V
BOOST
SW
V
IN
= 8V
V
IN
= 12V
V
OUT
10μF
OUT
WALL
LTC4098
V
C
BAT
+
SINGLE-CELL
Li-Ion
0.3
0.7
0.5
0.9
OUTPUT CURRENT(A)
1.1
1.3
3653 TA01a
3653f
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LINER [ LINEAR TECHNOLOGY ]
