LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
Monolithic 1.5A, 1.25MHz
Step-Down Switching Regulators
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DESCRIPTIO
FEATURES
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1.5A Switch in a Small MSOP Package
Constant 1.25MHz Switching Frequency
High Power Exposed Pad (MS8E) Package
Wide Operating Voltage Range: 3V to 25V
High Efficiency 0.22Ω Switch
1.2V Feedback Reference Voltage
Fixed Output Voltages of 1.8V, 2.5V, 3.3V, 5V
2% Overall Output Tolerance
Uses Low Profile Surface Mount Components
Low Shutdown Current: 6µA
Synchronizable to 2MHz
Current Mode Loop Control
Constant Maximum Switch Current Rating at All Duty
Cycles*
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APPLICATIO S
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DSL Modems
Portable Computers
Wall Adapters
Battery-Powered Systems
Distributed Power
The LT®1767 is a 1.25MHz monolithic buck switching
regulator. A high efficiency 1.5A, 0.22Ω switch is included
on the die together with all the control circuitry required to
complete a high frequency, current mode switching regulator. Current mode control provides fast transient response and excellent loop stability.
New design techniques achieve high efficiency at high
switching frequencies over a wide operating range. A low
dropout internal regulator maintains consistent performance over a wide range of inputs from 24V systems to LiIon batteries. An operating supply current of 1mA improves 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 1.4MHz to 2MHz.
The LT1767 is available in an 8-pin MSOP fused leadframe
package and a low thermal resistance exposed pad package. Full cycle-by-cycle short-circuit protection and thermal shutdown are provided. High frequency operation
allows the reduction of input and output filtering components and permits the use of chip inductors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*Patent Pending
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TYPICAL APPLICATIO
Efficiency vs Load Current
95
12V to 3.3V Step-Down Converter
D2
CMDSH-3
C3
2.2µF
CERAMIC
L1
5µH
BOOST
VIN
12V
VIN
OPEN
OR
HIGH
= ON
VSW
LT1767-3.3
SHDN
SYNC
OUTPUT
3.3V
1.2A*
EFFICIENCY (%)
C2
0.1µF
VIN = 10V
VOUT = 5V
90
85
VIN = 5V
VOUT = 3.3V
80
FB
GND
VC
CC
1.5nF
D1
UPS120
C1
10µF
CERAMIC
RC
4.7k
*MAXIMUM OUTPUT CURRENT IS SUBJECT TO THERMAL DERATING.
75
70
0
1767 TA01
0.2
0.4 0.6 0.8
1
LOAD CURRENT (A)
1.2
1.4
1767 TA01a
sn1767 1767fas
1
