n Wide Input Range: 3V to 25V
n Short-Circuit Protected Over Full Input Range
n 2A Output Current Capability
n Adjustable/Synchronizable Fixed Frequency
Operation from 250kHz to 2.2MHz
n Soft-Start/Tracking Capability
n Output Adjustable Down to 0.8V
n Adjustable Linear Regulator/Driver with 13mA
n Power Good Comparator with Complementary
n Low Shutdown Current: 12μA
n Thermally Enhanced 3mm × 3mm DFN Package
n Automotive Battery Regulation
n Industrial Control
n Wall Transformer Regulation
n Distributed Power Regulation
Monolithic 2A Step-Down
Regulator Plus Linear
The LT®1939 is a current mode PWM step-down DC/DC
converter with an internal 2.3A switch. The wide input
range of 3V to 25V makes the LT1939 suitable for regu-
lating power from a wide variety of sources, including
automotive batteries, industrial supplies and unregulated
Resistor-programmable 250kHz to 2.2MHz frequency
range and synchronization capability enable optimization
between efﬁciency and external component size. Cycle-
by-cycle current limit, frequency foldback and thermal
shutdown provide protection against a shorted output.
The soft-start feature controls the ramp rate of the output
voltage, eliminating input current surge during start-up,
and also provides output tracking.
The LT1939 contains an internal NPN transistor with feed-
back control which can be conﬁgured as a linear regulator
or as a linear regulator controller.
The LT1939’s low current shutdown mode (<12μA) enables
easy power management in battery-powered systems.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Dual Step-Down Converters
6V TO 25V
Switching Converter Efﬁciency
80 VOUT1 = 5V AT 1A
VIN = 12V
IOUT2 = 0A
FREQUENCY = 800kHz
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
LOAD CURRENT (A)
VOUT2 = 3.3V AT 1A
Output Voltage Ripple