LT1765 Datasheet, PDF (1/20 Pages) Linear Technology – Monolithic 3A, 1.25MHz Step-Down Switching Regulator

LT1765/LT1765-1.8/LT1765-2.5/
LT1765-3.3/LT1765-5
Monolithic 3A, 1.25MHz
Step-Down Switching Regulator
FEATURES
s _{3A Switch in a Thermally Enhanced 16-Lead}
TSSOP or 8-Lead SO Package
s _{Constant 1.25MHz Switching Frequency}
s _{Wide Operating Voltage Range: 3V to 25V}
s _{High Efficiency 0.09Ω Switch}
s _{1.2V Feedback Reference Voltage}
s _{Uses Low Profile Surface Mount Components}
s _{Low Shutdown Current: 15µA}
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 _{Regulated Wall Adapters}
s _{Battery-Powered Systems}
s _{Distributed Power}
, LTC and LT are registered trademarks of Linear Technology Corporation.
* Patent Pending
DESCRIPTIO
The LT^®1765 is a 1.25MHz monolithic buck switching
regulator. A high efficiency 3A, 0.09Ω switch is included
on the die together with all the control circuitry required
to construct 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 voltage range.
A low dropout internal regulator maintains consistent
performance over a wide range of inputs from 24V
systems to Li-Ion batteries. An operating supply current
of 1mA improves efficiency, especially at lower output
currents. Shutdown reduces quiescent current to 15µA.
Maximum switch current remains constant at all duty
cycles. Synchronization allows an external logic level
signal to increase the internal oscillator into the range of
1.6MHz to 2MHz.
Full cycle-by-cycle current control and thermal shutdown
are provided. High frequency operation allows the reduc-
tion of input and output filtering components and permits
the use of chip inductors.
TYPICAL APPLICATIO
INPUT
5V
2.2µF
CERAMIC
5V to 3.3V Step-Down Converter
CMDSH-3
OFF ON
0.18µF
BOOST
V_IN
V_SW
LT1765-3.3
SHDN
FB
SYNC GND V_C
2.2nF
1.5µH
UPS120
OUTPUT
3.3V
2.5A
4.7µF
CERAMIC
1765 TA01
Efficiency vs Load Current
90
V_IN = 10V
V_OUT = 5V
85
80
75
70
0
0.5
1.0
1.5
SWITCH CURRENT (A)
2.0
1765 • TAO1a
sn1765 1765fas
1