Texas Instruments LM3940 Low-Dropout (LDO) Fixed Voltage Regulator, 3.3V 1A, TO

The Texas Instruments LM3940IT-3.3/NOPB is a robust 1A low-dropout (LDO) voltage regulator engineered to deliver a stable 3.3V output from a standard 5V power supply. It is the ideal solution for mixed-voltage systems that operate with both 5V and 3.3V logic, particularly where primary power is sourced from a 5V bus. As a true low-dropout regulator, it maintains precise 3.3V output regulation even with input voltages as low as 4.5V, ensuring reliable performance as the supply voltage sags.

This regulator features excellent output voltage accuracy, with specifications detailing minimum and maximum output voltage error relative to the nominal 3.3V, and provides superb load regulation across varying conditions. For robust system protection, it incorporates multiple built-in safety mechanisms. An internal current limit circuit protects the regulator against high-load current faults or short-circuit events, during which it sources a constant current. Additionally, a thermal shutdown protection circuit disables the output when excessive heat is dissipated, safeguarding the device from damage. The regulator's rapid thermal response means it will cycle on and off at a high duty cycle if the thermal limit is sustained until the power dissipation is reduced.

Designed for ease of use, the LM3940 requires only one external component for operation. It is constructed as a green product, free from antimony and bromine (Sb/Br), aligning with modern environmental standards. Its through-hole TO-220 package ensures straightforward mounting and excellent thermal performance for heat dissipation.

Key Specifications

• Output Type: Fixed
• Output Voltage: 3.3V
• Maximum Output Current: 1A
• Input Voltage Range: 0V to 7.5V (4.5V to 5.5V for specified 3.3V operation)
• Typical Dropout Voltage: 500mV
• Operating Temperature Range: -40°C to +125°C
• Package: TO-220 (3-Pi