LT1961
1.5A, 1.25MHz Step-Up
Switching Regulator
FEATURES
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DESCRIPTIO
1.5A Switch in a Small MSOP Package
Constant 1.25MHz Switching Frequency
Wide Operating Voltage Range: 3V to 25V
High Efficiency 0.2Ω Switch
1.2V Feedback Reference Voltage
±2%
Overall Output Voltage Tolerance
Uses Low Profile Surface Mount External
Components
Low Shutdown Current: 6μA
Synchronizable from 1.5MHz to 2MHz
Current-Mode Loop Control
Constant Maximum Switch Current Rating at All Duty
Cycles*
Thermally Enhanced Exposed Pad 8-Lead Plastic
MSOP Package
The LT
®
1961 is a 1.25MHz monolithic boost switching
regulator. A high efficiency 1.5A, 0.2Ω switch is included
on the die together with all the control circuitry required to
complete a high frequency, current-mode switching regu-
lator. Current-mode control provides fast transient re-
sponse and excellent loop stability.
New design techniques achieve high efficiency at high
switching frequencies over a wide operating voltage range.
A low dropout internal regulator maintains consistent
performance over a wide range of inputs from 24V sys-
tems to Li-Ion batteries. An operating supply current of
1mA maintains high efficiency, especially at lower output
currents. Shutdown reduces quiescent current to 6μA.
Maximum switch current remains constant at all duty
cycles. Synchronization allows an external logic level
signal to increase the internal oscillator from 1.5MHz to
2MHz.
The LT1961 is available in an exposed pad, 8-pin MSOP
package. Full cycle-by-cycle switch current limit protec-
tion and thermal shutdown are provided. High frequency
operation allows the reduction of input and output filtering
components and permits the use of chip inductors.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. *Patent Pending
APPLICATIO S
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DSL Modems
Portable Computers
Battery-Powered Systems
Distributed Power
TYPICAL APPLICATIO
6.8μH
5V to 12V Boost Converter
UPS120
V
IN
5V
2.2μF
CERAMIC
1
V
IN
V
SW
2
90.9k
LT1961
OPEN
OR 5
6
SHDN
FB
HIGH
SYNC GND V
C
= ON
8
3,4
7
6800pF
100pF
6.8k
EFFICIENCY (%)
V
OUT
12V
0.5A*
10k
1%
10μF
CERAMIC
*MAXIMUM OUTPUT CURRENT IS SUBJECT TO THERMAL DERATING.
1961 TA01
U
Efficiency vs Load Current
90
85
80
75
70
65
60
V
IN
= 5V
V
OUT
= 12V
0
100
200
300
400
LOAD CURRENT (mA)
500
1961 TA01a
U
U
1961fa
1
LINER [ LINEAR TECHNOLOGY ]
