LT1512
SEPIC Constant-Current/
Constant-Voltage Battery Charger
Fea T Descrip T
n
Charger Input Voltage May Be Higher, Equal to or
The LT 1512 is a 500kHz current mode switching regulator
Lower Than Battery Voltage
specially configured to create a constant-current/constant-
n
Charges Any Number of Cells Up to 30V*
voltage battery charger. In addition to the usual voltage
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1% Voltage Accuracy for Rechargeable Lithium
feedback node, it has a current sense feedback circuit for
Batteries
accurately controlling output current of a flyback or SEPIC
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500kHz Switching Frequency Minimizes
(Single-Ended Primary Inductance Converter) topology
Inductor Size
charger. These topologies allow the current sense circuit
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100mV Current Sense Voltage for High Efficiency
to be ground referred and completely separated from the
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Battery Can Be Directly Grounded
battery itself, simplifying battery switching and system
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Charging Current Easily Programmable or Shut Down
grounding problems. In addition, these topologies allow
charging even when the input voltage is lower than the
battery voltage.
a T
Maximum switch current on the LT1512 is 1.5A. This allows
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Battery Charging of NiCd, NiMH, Lead-Acid or
battery charging currents up to 1A for a single lithium-ion
Lithium Rechargeable Cells
cell. Accuracy of 1% in constant-voltage mode is perfect
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Precision Current Limited Power Supply
for lithium battery applications. Charging current can be
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Constant-Voltage/Constant-Current Supply
easily programmed for all battery types.
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Transducer Excitation
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Maximum Input Voltage = 40V V
BAT
Typical a T
Maximum Charging Current
L1 A*
WALL
1.0
ADAPTER
C2** D1
SINGLE
+ C3
INPUT 2.2F
MBRS130LT3
LITHIUM
22F
V
IN
0.8
V CELL (4.1V)
25V SW 0.5A
CHARGE
L1 B*
SYNC LT1512
R1
0.6
DOUBLE
AND/OR
S/S
LITHIUM
SHUTDOWN FB
CELL (8.2V)
SHUTDOWN
GND GND S V I
C FB +
C1
R4
R2
0.4
22F 6V BATTERY
24
25V
C5
0.1F
12V BATTERY
0.2
R3
R5
C4
0.2
1k
0.22F
INDUCTOR = 33H
0
0 5 10 15 20 25
*L1 A, L1 B ARE TWO 33H WINDINGS ON A
SINGLE INDUCTOR: COILTRONICS CTX33-3
INPUT VOLTAGE (V)
1512 F01
**TOKIN CERAMIC 1E225ZY5U-C203-F
1512 TA02
ACTUAL PROGRAMMED CHARGING CURRENT w ILL BE INDEPENDENT OF INPUT
VOLTAGE AND BATTERy VOLTAGE IF IT DOES NOT ExCEED THE VALUES SHOw N.
Figure 1. SEPIC Charger with 0.5A Output Current
THESE ARE ELECTRICAL LIMITATIONS BASED ON MAxIMUM Sw ITCH CURRENT.
PACKAGE THERMAL LIMITATIONS MAy REDUCE MAxIMUM CHARGING CURRENT.
SEE APPLICATIONS INFORMATION.
1512fc
1
For more information www.linear.com/LT1512
CURRENT (A)
ion pplica
ions pplica
ion uresLT1512
a Te Maxi Mu M r a T p in c F T
(Note 1)
TOP VIEW
Input Voltage ........................................................... 30V
V V
1 8
C SW
Switch Voltage ......................................................... 40V
FB 2 7 GND
S/S Pin Voltage ........................................................ 30V
I 3 6 GND S
FB
FB Pin Voltage (Transient, 10ms) ........................... 10V
S/S V
4 5
IN
V Pin Current ..................................................... 10mA
FB
I Pin Voltage (Transient, 10ms) .......................... 10V N8 PACKAGE S8 PACKAGE
FB
8-LEAD PDIP 8-LEAD PLASTIC SO
Storage Temperature Range .................. 65C to 150C
T = 125C, q = 100C/w (N)
JMAx JA
Ambient Temperature Range
T = 125C, q = 130C/w (S)
JMAx JA
LT1512C (Note 2) ..................................... 0C to 70C
NOTE: CONTACT FACTORy CONCERNING 16-LEAD
FUSED-LEAD GN PACKAGE w ITH LOw ER THERMAL RESISTANCE
LT1512I ................................................ 40C to 85C
Operating Junction Temperature Range
LT1512C (Note 2) .............................. 20C to 125C
LT1512I .............................................. 40C to 125C
Short Circuit.......................................... 0C to 150C
Lead Temperature (Soldering, 10 sec) ................. 300C
Der in F Ma T
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1512CN8#PBF LT1512CN8#TRPBF 1512 8-Lead PDIP 0C to 70C
LT1512CS8#PBF LT1512CS8#TRPBF 1512 8-Lead Plastic SO 0C to 70C
LT1512IN8#PBF LT1512IN8#TRPBF 1512I 8-Lead PDIP 40C to 85C
LT1512IS8#PBF LT1512IS8#TRPBF 1512I 8-Lead Plastic SO 40C to 85C
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1512CN8 LT1512CN8#TR 1512 8-Lead PDIP 0C to 70C
LT1512CS8 LT1512CS8#TR 1512 8-Lead Plastic SO 0C to 70C
LT1512IN8 LT1512IN8#TR 1512I 8-Lead PDIP 40C to 85C
LT1512IS8 LT1512IS8#TR 1512I 8-Lead Plastic SO 40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: