The LT1939 is a current mode PWM step-down DC/DC converter with an internal 2.3A switch. It is suitable for regulating power from a wide variety of sources (including automotive batteries, industrial supplies, and unregulated wall adapters). The adjustable/synchronizable fixed frequency operation from 250kHz to 2.2MHz allows for optimization between efficiency and external component size. It provides protection against a shorted output through cycle-by-cycle current limit, frequency foldback, and thermal shutdown. 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 feedback control which can be configured as a linear regulator or as a linear regulator controller. Its low current shutdown mode (<12μA) enables easy power management in battery-powered systems.
The LT1939 is a monolithic 2 A step‑down regulator that operates from a wide input range of 3 V to 25 V. It offers an adjustable output down to 0.8 V, a soft‑start feature, and a low shutdown current of 12 µA, making it suitable for automotive, industrial, and wall‑adapter applications.
The device is supplied in a 12‑lead 3 mm × 3 mm plastic DFN package with an exposed pad for thermal management. Detailed electrical characteristics include a shutdown threshold of about 760 mV, a switching frequency range of 250 kHz to 2.2 MHz, and protection features such as short‑circuit protection and thermal shutdown.
| Input voltage range | 3 V to 25 V |
|---|---|
| Maximum output current | 2 A |
| Adjustable output voltage | 0.8 V to Vin |
| Shutdown threshold (typical) | 760 mV |
| Low shutdown current | 12 µA |
| Switching frequency range | 250 kHz to 2.2 MHz |
| Package type | 12‑lead 3 mm × 3 mm plastic DFN |
The LT1939 operates from 3 V up to 25 V.
The typical shutdown threshold is about 760 mV.
It is supplied in a 12‑lead 3 mm × 3 mm plastic DFN package.
The device can deliver up to 2 A of output current.