Datasheet LT1939 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| Pages / Page | 24 / 1 — FEATURES. DESCRIPTION. Wide Input Range: 3V to 25V. Short-Circuit … |
| File Format / Size | PDF / 358 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide Input Range: 3V to 25V. Short-Circuit Protected Over Full Input Range. 2A Output Current Capability
Model Line for this Datasheet
Text Version of Document
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 250kHz to 2.2MHz
automotive batteries, industrial supplies and unregulated n
Soft-Start/Tracking Capability
wall adapters. n
Output Adjustable Down to 0.8V
Resistor-programmable 250kHz to 2.2MHz frequency n
Adjustable Linear Regulator/Driver with 13mA
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,
APPLICATIONS
and also provides output tracking. 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 Switching Converter Effi ciency Output Voltage Ripple
BAT54 90 VIN V BST 6V TO 25V IN 85 0.47μF 2.2μF LT1939 6.8μH VOUT1 80 VOUT1 = 5V AT 1A SW 5V AC COUPLED B240A 1A 75 2mV/DIV SHDN 42.2k SS 22μF 70 0.47μF FB PG 8.06k 65 EFFICIENCY (%) PG VOUT2 = 3.3V AT 1A 60 AC COUPLED R 2mV/DIV T/SYNC LDRV V 55 IN = 12V 53.6k V I C OUT2 = 0A 1k FREQUENCY = 800kHz 330pF 24.9k VOUT2 50 LFB 3.3V 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 500ns/DIV 1939 TA01c 40.2k 1A 8.06k 22μF LOAD CURRENT (A) 1939 TA01b 1939 TA01a 1939f 1
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 250kHz to 2.2MHz
automotive batteries, industrial supplies and unregulated n
Soft-Start/Tracking Capability
wall adapters. n
Output Adjustable Down to 0.8V
Resistor-programmable 250kHz to 2.2MHz frequency n
Adjustable Linear Regulator/Driver with 13mA
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,
APPLICATIONS
and also provides output tracking. 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 Switching Converter Effi ciency Output Voltage Ripple
BAT54 90 VIN V BST 6V TO 25V IN 85 0.47μF 2.2μF LT1939 6.8μH VOUT1 80 VOUT1 = 5V AT 1A SW 5V AC COUPLED B240A 1A 75 2mV/DIV SHDN 42.2k SS 22μF 70 0.47μF FB PG 8.06k 65 EFFICIENCY (%) PG VOUT2 = 3.3V AT 1A 60 AC COUPLED R 2mV/DIV T/SYNC LDRV V 55 IN = 12V 53.6k V I C OUT2 = 0A 1k FREQUENCY = 800kHz 330pF 24.9k VOUT2 50 LFB 3.3V 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 500ns/DIV 1939 TA01c 40.2k 1A 8.06k 22μF LOAD CURRENT (A) 1939 TA01b 1939 TA01a 1939f 1
