LINEAR TECHNOLOGY - LT1939 User Guide
Summary
This versatile power management IC is a high-efficiency step-down DC/DC regulator seamlessly integrated with linear control features. Designed for robust performance across wide input voltage ranges (3V–25V), it provides critical protections, including soft-start and short-circuit coverage. Technical specifications detail its suitability for professional engineers developing complex power solutions in automotive, industrial, or distributed battery systems.
Page 1 Text Content
LT1939
Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller
FEATURES DESCRIPTION n Wide Input Range: 3V to 25V
The LT®1939 is a current mode PWM step-down DC/DC
n Short-Circuit Protected Over Full Input Range
converter with an internal 2.3A switch. The wide input
n 2A Output Current Capability
range of 3V to 25V makes the LT1939 suitable for regu-
n Adjustable/Synchronizable Fixed Frequency
lating power from a wide variety of sources, including
Operation from 250k Hz to 2.2MHz automotive batteries, industrial supplies and unregulated n Soft-Start/Tracking Capability
wall adapters.
FF IC IE
n Output Adjustable Down to 0.8V
Resistor-programmable 250k Hz to 2.2MHz frequency
n Adjustable Linear Regulator/Driver with 13m A
range and synchronization capability enable optimization
Output Capability
between effi ciency and external component size. Cycle-
n Power Good Comparator with Complementary
by-cycle current limit, frequency foldback and thermal
Outputs
shutdown provide protection against a shorted output.
n Low Shutdown Current: 12μA
The soft-start feature controls the ramp rate of the output
n Thermally Enhanced 3mm × 3mm DFN Package
voltage, eliminating input current surge during start-up, and also provides output tracking.
APPLICATIONS
The LT1939 contains an internal NPN transistor with feed-
n Automotive Battery Regulation
back control which can be confi gured as a linear regulator
n Industrial Control
or as a linear regulator controller.
n Wall Transformer Regulation
n Distributed Power Regulation 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.
TYPICAL APPLICATION Dual Step-Down Converters Output Voltage Ripple Switching Converter Effi ciency
BAT54
BSTVIN
6V TO 25V
LT1939
6.8μH VOUT1 VOUT1 = 5V AT 1A
SW 5V AC COUPLED
B240A 1A 2m V/DIV
SS 22μF
0.47μF FB
PG 8.06k
PG VOUT2 = 3.3V AT 1A AC COUPLED
2m V/DIV
RT/SYNC LDRV VIN = 12V
VC IOUT2 = 0A
FREQUENCY = 800k Hz
330p F 24.9k VOUT2
LFB 3.3V 1939 TA01c
0.4 0.6 0.8 1.0 1.2 1.6 1.8 2.01.40.2 500ns/DIV
40.2k 1A 8.06k 22μF LOAD CURRENT (A)
1939 TA01b
1939 TA01a
Page Summary Contents For LINEAR TECHNOLOGY - LT1939 User Guide
Manual Details
| Brand | Linear |
|---|---|
| Pages | 24 |
| File Size | 359.79 KB |
| Published | June 16, 2026 |
Enter the captcha to get the download link:
Frequently Asked Questions
What is the minimum input voltage range for the LT1939?
The LT1939 operates from a wide input range of 3V to 25V.
Can the device be used with automotive batteries?
Yes, the LT1939 features an NPN internal transistor, allowing it for Automotive Battery Regulation applications.
How does power good monitoring help prevent issues?
The Power Good Comparator detects a shorted output and the outputs shutdown to provide protection against such events.
What is the adjustable output voltage capability?
The output can be resistor-programmable and adjusted down to 0.8V.