STMicroelectronics L7905CD2T

Overview

L7905CD2T from STMicroelectronics is a three-terminal fixed-output negative voltage regulator delivering -5 V at up to 1.5 A, featuring thermal overload protection, short-circuit protection, and output transition SOA protection. It operates with input voltages down to -35 V, supports local on-card regulation for split-supply systems, and is commonly used in dual-rail analog power supplies for op-amp circuits.

For engineers reviewing the L7905CD2T datasheet, L7905CD2T pinout, L7905CD2T application, or L7905CD2T equivalent, key selection criteria include guaranteed -5 V output accuracy (±50 mV over load/line), dropout voltage of 1.4 V at 1 A, junction-to-ambient thermal resistance of 62.5 °C/W in D²PAK, and compatibility with standard ±15 V split-supply designs.

Technical Context

The L7905CD2T implements a monolithic PNP pass transistor architecture with internal current limiting, thermal shutdown, and safe operating area (SOA) protection during transient overload. Its feedback loop maintains regulation across input variations from -8 V to -20 V and load currents from -5 mA to -1.5 A.

Designed for fixed-voltage operation, it requires no external components for basic functionality but supports adjustable output configurations via external resistors. The device's SOA protection prevents latch-up during momentary short circuits or high-dV/dt transients at the input.

Key Specifications

Pinout & Package

Supplied in D²PAK (TO-263) surface-mount package with exposed thermal pad for enhanced heat dissipation. Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output - verified per Figure 2 (top view) and Table 8 mechanical data in ST Doc ID 2149 Rev 21.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative fixed-voltage regulator applications.

Compared with LM7905CT and MC7905BD2TG, the L7905CD2T offers superior thermal performance in D²PAK (R_thJA = 62.5 °C/W vs 50 °C/W for TO-220), lower dropout (1.4 V), and tighter load regulation (50 mV), making it optimal for space-constrained industrial analog boards requiring robust thermal behavior.

Availability

L7905CD2T is available at Aetrix Electronics and suitable for industrial PLC analog I/O modules, audio power amplifier bias rails, split-supply op-amp circuits, and legacy RS-232 transceiver biasing requiring stable component supply and long-term manufacturability.

Supply support for L7905CD2T 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, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The L79xxC series was developed specifically for cost-sensitive, high-reliability linear regulation in industrial control and analog signal conditioning applications, emphasizing ruggedness, thermal safety, and drop-in compatibility with legacy 79xx designs.

FAQ

What is the minimum input voltage required for stable -5 V output?

The L7905CD2T requires a minimum input voltage of -6.4 V to maintain regulation at 1 A output, based on its 1.4 V dropout specification. For reliable operation across temperature and load extremes, ST recommends VI ≥ -7 V. Operation below -6.4 V causes output collapse into dropout, where VO tracks VI minus dropout voltage.

Can this regulator be used without an output capacitor?

No - an output capacitor of at least 1 µF solid tantalum (or ≥10 µF aluminum electrolytic) is mandatory for stability, as confirmed in Figure 4 and Section 6 of ST Doc ID 2149. Omitting CO risks oscillation, excessive noise, and potential thermal runaway during load transients.

Does the D²PAK package require solder paste stencil optimization?

Yes - the D²PAK's exposed thermal pad (Pin 2) demands controlled solder volume: ST recommends a 70–80% window-pane stencil aperture with 0.12 mm thickness to ensure void-free thermal interface while avoiding solder bridging to adjacent pins. IPC-7351B land pattern (Table 10) must be followed precisely.

How does thermal shutdown behave during sustained overload?

When junction temperature reaches 150 °C, the L7905CD2T disables the pass transistor and holds output at zero until T_J falls below ~135 °C (typical hysteresis of 15 °C). This cycle repeats autonomously - no external reset is needed - protecting against permanent damage during prolonged short-circuit events.