FEATURES
n Wide Input Voltage Range: 4.5V to 45V
n Tolerant of 60V Input Transients
n Internal High Side and Low Side Power Switches
n No Compensation Required
n 50mA Output Current
n Low Dropout Operation: 100% Duty Cycle
n Low Quiescent Current: 12µA
n 0.8V Feedback Voltage Reference
n Adjustable Peak Current Limit
n Internal and External Soft-Start
n Precise RUN Pin Threshold with Adjustable
Hysteresis
n 3.3V, 5V and Adjustable Output Versions
n Only Three External Components Required for Fixed
Output Versions
n Low Profile (0.75mm) 3mm × 3mm DFN and
Thermally-Enhanced MS8E Packages
APPLICATIONS
n 4mA to 20mA Current Loops
n Industrial Control Supplies
n Distributed Power Systems
n Portable Instruments
n Battery-Operated Devices
n Automotive Power Systems
LTC3642
High Efficiency, High Voltage
50mA Synchronous
Step-Down Converter
DESCRIPTION
The LTC®3642 is a high efficiency, high voltage step-down
DC/DC converter with internal high side and synchronous
power switches that draws only 12μA typical DC sup-
ply current at no load while maintaining output voltage
regulation.
The LTC3642 can supply up to 50mA load current and
features a programmable peak current limit that provides
a simple method for optimizing efficiency in lower current
applications. The LTC3642’s combination of Burst Mode®
operation, integrated power switches, low quiescent cur-
rent, and programmable peak current limit provides high
efficiency over a broad range of load currents.
With its wide 4.5V to 45V input range and internal
overvoltage monitor capable of protecting the part through
60V surges, the LTC3642 is a robust converter suited for
regulating a wide variety of power sources. Additionally,
the LTC3642 includes a precise run threshold and soft‑start
feature to guarantee that the power system start-up is
well-controlled in any environment.
The LTC3642 is available in the thermally enhanced
3mm × 3mm DFN and MS8E packages.
L, LT, LTC, LTM, Burst Mode, Linear Technology, and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
5V, 50mA Step-Down Converter
VIN
5V TO 45V
1µF
VIN
SW
LTC3642-5
RUN
HYST
VOUT
SS
ISET
GND
150µH
3642 TA01a
VOUT
5V
10µF 50mA
Efficiency and Power Loss vs Load Current
100
VIN = 10V
95
100
EFFICIENCY
90
85
10
POWER LOSS
80
75
1
70
65
0.1
1
10
LOAD CURRENT (mA)
0.1
100
3642 TA01b
3642fc
1
