LT1961
1.5A, 1.25MHz Step-Up
Switching Regulator
FEATURES
DESCRIPTIO
1.5A Switch in a Small MSOP Package The LT 1961 is a 1.25MHz monolithic boost switching
Constant 1.25MHz Switching Frequency regulator. A high efficiency 1.5A, 0.2 switch is included
Wide Operating Voltage Range: 3V to 25V on the die together with all the control circuitry required to
High Efficiency 0.2 Switch complete a high frequency, current-mode switching regu-
1.2V Feedback Reference Voltage lator. Current-mode control provides fast transient re-
2% Overall Output Voltage Tolerance sponse and excellent loop stability.
Uses Low Profile Surface Mount External
New design techniques achieve high efficiency at high
Components
switching frequencies over a wide operating voltage range.
Low Shutdown Current: 6 A
A low dropout internal regulator maintains consistent
Synchronizable from 1.5MHz to 2MHz
performance over a wide range of inputs from 24V sys-
Current-Mode Loop Control
tems to Li-Ion batteries. An operating supply current of
Constant Maximum Switch Current Rating at All Duty
1mA maintains high efficiency, especially at lower output
Cycles*
currents. Shutdown reduces quiescent current to 6A.
Thermally Enhanced Exposed Pad 8-Lead Plastic
Maximum switch current remains constant at all duty
MSOP Package
cycles. Synchronization allows an external logic level
U
signal to increase the internal oscillator from 1.5MHz to
APPLICATIO S
2MHz.
DSL Modems
The LT1961 is available in an exposed pad, 8-pin MSOP
Portable Computers
package. Full cycle-by-cycle switch current limit protec-
Battery-Powered Systems
tion and thermal shutdown are provided. High frequency
Distributed Power
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
TYPICAL APPLICATIO
Efficiency vs Load Current
5V to 12V Boost Converter
90
6.8H
85
UPS120
V
OUT
1 2 80
V
IN
12V
V V
IN SW
5V
0.5A*
LT1961
2.2F
90.9k
OPEN
75
CERAMIC
OR 5 6
SHDN
FB
HIGH
V
SYNC GND C
70
= ON
8 3,4 7
10F
10k
6800pF CERAMIC
65
1%
100pF
V = 5V
IN
6.8k
V = 12V
OUT
60
0 100 200 300 400 500
*MAXIMUM OUTPUT CURRENT IS SUBJECT TO THERMAL DERATING.
1961 TA01 LOAD CURRENT (mA)
1961 TA01a
1961fa
1
EFFICIENCY (%)
U
ULT1961
ABSOLUTE MAXIMUM RATINGS
PI CO FIGURATIO
(Note 1)
TOP VIEW
Input Voltage .......................................................... 25V
V 1 8 SYNC
IN
Switch Voltage ......................................................... 35V
SW 2 7 V
C
SHDN Pin ............................................................... 25V GND 3 6 FB
GND 4 5 SHDN
FB Pin Current ....................................................... 1mA
MS8E PACKAGE
SYNC Pin Current .................................................. 1mA
8-LEAD PLASTIC MSOP
Operating Junction Temperature Range (Note 2)
GROUND PAD CONNECTED
TO LARGE COPPER AREA
LT1961E, LT1961I ........................... 40C to 125C
T = 125C, = 50C/W
JMAX JA
Storage Temperature Range ................ 65C to 150C
Lead Temperature (Soldering, 10 sec)................. 300C
UUW
ORDER I FOR ATIO
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1961EMS8E#PBF LT1961EMS8E#TRPBF LTQY 8-Lead Plastic MSOP 40C to 125C
LT1961IMS8E#PBF LT1961IMS8E#TRPBF LTQY 8-Lead Plastic MSOP 40C to 125C
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1961EMS8E LT1961EMS8E#TR LTQY 8-Lead Plastic MSOP 40C to 125C
LT1961IMS8E LT1961IMS8E#TR LTQY 8-Lead Plastic MSOP 40C to 125C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container.
For more information on lead free part marking, go to: