LT1767 Datasheet, PDF (1/16 Pages) Linear Technology – Monolithic 1.5A, 1.25MHz Step-Down Switching Regulators

LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
Monolithic 1.5A, 1.25MHz
Step-Down Switching Regulators
FEATURES
s _{1.5A Switch in a Small MSOP Package}
s _{Constant 1.25MHz Switching Frequency}
s _{High Power Exposed Pad (MS8E) Package}
s _{Wide Operating Voltage Range: 3V to 25V}
s _{High Efficiency 0.22Ω Switch}
s _{1.2V Feedback Reference Voltage}
s _{Fixed Output Voltages of 1.8V, 2.5V, 3.3V, 5V}
s _{2% Overall Output Tolerance}
s _{Uses Low Profile Surface Mount Components}
s _{Low Shutdown Current: 6µA}
s _{Synchronizable to 2MHz}
s _{Current Mode Loop Control}
s _{Constant Maximum Switch Current Rating at All Duty}
Cycles*
U
APPLICATIO S
s _{DSL Modems}
s _{Portable Computers}
s _{Wall Adapters}
s _{Battery-Powered Systems}
s _{Distributed Power}
DESCRIPTIO
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 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 range. A low
dropout internal regulator maintains consistent perfor-
mance over a wide range of inputs from 24V systems to Li-
Ion batteries. An operating supply current of 1mA im-
proves efficiency, especially at lower output currents.
Shutdown reduces quiescent current to 6µA. Maximum
switch current remains constant at all duty cycles. Syn-
chronization allows an external logic level signal to in-
crease 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 pack-
age. Full cycle-by-cycle short-circuit protection and ther-
mal shutdown are provided. High frequency operation
allows the reduction of input and output filtering compo-
nents and permits the use of chip inductors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*Patent Pending
TYPICAL APPLICATIO
12V to 3.3V Step-Down Converter
D2
CMDSH-3
V_IN
12V _C3
2.2µF
CERAMIC
OPEN
OR
HIGH
= ON
C2
0.1µF
BOOST
V_IN
V_SW
LT1767-3.3
SHDN
FB
SYNC GND V_C
C_C
1.5nF
R_C
4.7k
L1
5µH
D1
UPS120
*MAXIMUM OUTPUT CURRENT IS SUBJECT TO THERMAL DERATING.
OUTPUT
3.3V
1.2A*
C1
10µF
CERAMIC
1767 TA01
Efficiency vs Load Current
95
V_IN = 10V
90
V_OUT = 5V
85
V_IN = 5V
80
V_OUT = 3.3V
75
70
0
0.2 0.4 0.6 0.8 1
LOAD CURRENT (A)
1.2 1.4
1767 TA01a
sn1767 1767fas
1