LT1956/LT1956-5
High Voltage, 1.5A,
500kHz Step-Down
Switching Regulators
FEATURES
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DESCRIPTIO
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Wide Input Range: 5.5V to 60V
1.5A Peak Switch Current
Small 16-Pin SSOP or Thermally Enhanced
TSSOP Package
Saturating Switch Design: 0.2Ω
Peak Switch Current Maintained Over
Full Duty Cycle Range
Constant 500kHz Switching Frequency
Effective Supply Current: 2.5mA
Shutdown Current: 25µA
1.2V Feedback Reference (LT1956)
5V Fixed Output (LT1956-5)
Easily Synchronizable
Cycle-by-Cycle Current Limiting
The LT
®
1956/LT1956-5 are 500kHz monolithic buck
switching regulators with an input voltage capability up to
60V. A high efficiency 1.5A, 0.2Ω switch is included on the
die along with all the necessary oscillator, control and logic
circuitry. A current mode architecture provides fast tran-
sient response and good loop stability.
Special design techniques and a new high voltage process
achieve high efficiency over a wide input range. Efficiency
is maintained over a wide output current range by using the
output to bias the circuitry and by utilizing a supply boost
capacitor to saturate the power switch. Patented circuitry
maintains peak switch current over the full duty cycle
range*. A shutdown pin reduces supply current to 25µA and
the device can be externally synchronized from 580kHz to
700kHz with a logic level input.
The LT1956/LT1956-5 are available in fused-lead 16-pin
SSOP and thermally enhanced TSSOP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*U.S. PATENT NO. 6,498,466
APPLICATIO S
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High Voltage, Industrial and Automotive
Portable Computers
Battery-Powered Systems
Battery Chargers
Distributed Power Systems
TYPICAL APPLICATIO
5V Buck Converter
MMSD914TI
6
V
IN
12V
(TRANSIENTS
TO 60V)
BOOST
4
2.2µF
100V
CERAMIC
15
14
†
0.1µF
SW
2
10µH
10MQ060N
10
12
EFFICIENCY (%)
V
IN
LT1956-5
SHDN
SYNC
GND
V
OUT
5V
1A
22µF
6.3V
CERAMIC
BIAS
FB
V
C
1, 8, 9, 16 11
220pF
4.7k
4700pF
†
UNITED CHEMI-CON THCS50EZA225ZT
1956 TA01
U
Efficiency vs Load Current
100
V
IN
= 12V
L = 18µH
90
V
OUT
= 5V
V
OUT
= 3.3V
80
70
60
50
0
0.25
0.75
1.00
0.50
LOAD CURRENT (A)
1.25
1956 TA02
U
U
1956f
1
LINER [ LINEAR TECHNOLOGY ]
