STMicroelectronics L7805T

Overview

L7805T from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering 5 V ±2 % output at up to 1.5 A, featuring thermal overload protection, short-circuit protection, and safe operating area (SOA) protection. It operates with input voltages up to 35 V (for 5 V output), supports junction temperatures from 0 °C to 125 °C, and is commonly used for local on-card regulation in industrial power supplies and embedded control modules.

For engineers reviewing the L7805T datasheet, L7805T pinout, L7805T application, or L7805T equivalent, key selection considerations include dropout voltage (2 V at 1 A), load regulation (≤100 mV over 5 mA–1.5 A), quiescent current (8 mA typical), and thermal resistance (R_thJA = 50 °C/W in TO-220 package).

Technical Context

The L7805T implements a monolithic series-pass linear regulation architecture with internal current limiting, thermal shutdown, and SOA protection-enabling robust operation without external protection circuitry. Its feedback loop maintains stable 5 V output across line (VI = 7–25 V) and load (IO = 5 mA–1.5 A) variations.

Designed for fixed-output use, it requires only two external capacitors (CI = 0.33 µF, CO = 0.1 µF) for stability per test circuits in DS0422. The device exhibits 62 dB supply voltage rejection at 120 Hz and 10 µV/√Hz output noise density (10 Hz–100 kHz bandwidth).

Key Specifications

Pinout & Package

Supplied in TO-220 package (3-lead, vertical mounting, metal tab connected to GND), the L7805T uses standard three-terminal configuration: Input (VI), Ground (GND), and Output (VO). The metal tab is electrically tied to Pin 2 (GND), enabling direct heatsink attachment without isolation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output linear regulator applications.

Compared with LM7805CDT/NOPB, the L7805T offers lower R_thJA (50 vs. 55 °C/W) for better thermal headroom at 1.5 A; versus MC7805BDTRKG, it lacks AEC-Q100 certification but provides identical electrical performance at lower cost for non-automotive use.

Availability

L7805T is available at Aetrix Electronics and suitable for industrial PLC power rails, automotive body control modules, medical diagnostic instrumentation, and point-of-sale terminal logic supplies requiring stable component supply, long-lifecycle support, and consistent parametric performance.

Supply support for L7805T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The L78 series belongs to ST's legacy positive voltage regulator ICs product line, designed specifically for cost-effective, robust local regulation in space- and reliability-constrained embedded systems.

FAQ

What is the minimum input voltage required for the L7805T to regulate 5 V?

The L7805T requires a minimum input voltage of 7 V to maintain regulation at full load (1.5 A), based on its 2 V dropout voltage specification at 1 A and derated behavior at higher currents. At light loads (<50 mA), regulation is maintained down to ~6.5 V, but design margin mandates VI ≥ 7.5 V for reliable operation across temperature and line variation.

Can the L7805T be used without an input bypass capacitor?

No - STMicroelectronics specifies a minimum 0.33 µF ceramic capacitor between input and ground, placed as close as possible to Pin 1 and Pin 2. Omitting it risks high-frequency oscillation due to parasitic inductance in the input trace, especially when sourced from a remote or inductive supply like a switcher output or long cable run.

Does the L7805T require a heat sink for 1 A continuous operation?

Yes - at 1 A with VI = 12 V, power dissipation is (12 − 5) × 1 = 7 W. With R_thJA = 50 °C/W, junction temperature rise would exceed 350 °C above ambient - far beyond the 125 °C limit. A heatsink reducing R_thJA to ≤20 °C/W (e.g., 10 cm² aluminum finned) is mandatory for safe 1 A operation at 25 °C ambient.

How does the L7805T behave during output short-circuit conditions?

Under sustained short-circuit, the L7805T limits output current to ~0.75 A (typical), then activates thermal shutdown if junction temperature exceeds ~165 °C. Once cooled below ~145 °C, it automatically recovers. This cycle repeats until the fault is removed - protecting both the IC and upstream supply without requiring external current-limiting components.