STMicroelectronics L7905ACD2T

Overview

L7905ACD2T from STMicroelectronics is a fixed-output, three-terminal negative linear voltage regulator delivering -5 V at up to 1.5 A, featuring thermal overload protection, short-circuit protection, and output transition SOA protection. It is housed in a D2PAK package and designed for local on-card regulation in split-power-supply systems alongside L78xxA positive regulators.

For engineers reviewing the L7905ACD2T datasheet, L7905ACD2T pinout, L7905ACD2T application, or L7905ACD2T equivalent, key selection criteria include guaranteed -5 V output accuracy over temperature and load, dropout voltage of 1.4 V at 1 A, supply voltage rejection of 54–60 dB at 120 Hz, and junction temperature operation from 0 °C to 125 °C.

Technical Context

This device implements a monolithic PNP pass transistor-based linear regulation architecture with internal current limiting, thermal shutdown, and safe operating area (SOA) protection during output transients. Its fixed -5 V output is trimmed at the wafer level to ±2% tolerance at 25 °C and maintains ±4% across full load (5 mA–1.5 A) and input voltage (–8 V to –20 V) ranges.

The regulator operates with minimal external components: a 2.2 µF input capacitor (solid tantalum recommended) and 1 µF output capacitor ensure stability and transient response. It supports adjustable configurations via external resistors but is optimized for fixed-voltage use in industrial and embedded power rails requiring low-noise, high-rejection negative supplies.

Key Specifications

Pinout & Package

The L7905ACD2T is supplied in a surface-mount D2PAK (TO-263) package with exposed thermal pad for enhanced heat dissipation. The package measures 10.0 mm × 15.25 mm × 4.60 mm and features gull-wing leads compatible with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7905CT and MC7905BD2TR4, the L7905ACD2T offers tighter initial output accuracy (±2% vs. ±4%), superior supply rejection (54–60 dB), and identical D2PAK packaging - making it optimal for new designs demanding precision and low noise in space-constrained industrial PCBs.

Availability

L7905ACD2T is available at Aetrix Electronics and suitable for industrial control PLC I/O modules, bipolar op-amp power rails, medical sensor signal conditioning, and legacy instrumentation requiring stable component supply with long-term lifecycle support.

Supply support for L7905ACD2T 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 automotive, industrial, and power management solutions with vertical manufacturing capabilities.

The L79xxAC series belongs to ST's legacy linear regulator product line, engineered specifically for robust, cost-effective negative voltage regulation in industrial and embedded systems where reliability and thermal resilience are critical.

FAQ

What is the minimum input voltage required for stable -5 V output at 1.5 A?

The L7905ACD2T requires a minimum input voltage of -6.4 V to maintain regulation at 1.5 A, calculated from its 1.4 V dropout voltage plus the nominal -5 V output. Operation below this threshold causes output collapse; for margin, -7 V or lower is recommended under worst-case temperature and load conditions.

Can the L7905ACD2T be used in adjustable configurations?

Yes - though optimized for fixed -5 V operation, the L7905ACD2T can be configured as an adjustable regulator using two external resistors per Figure 6 in the datasheet. The GND pin becomes the ADJ node, and output voltage is set by VO = -5 V × (1 + R1/R2), with R2 connected between OUT and ADJ.

Is a heat sink required for 1.5 A continuous operation?

Yes - at 1.5 A with a 5 V output and typical -12 V input, power dissipation exceeds 10 W. With R_thJA = 62.5 °C/W, junction temperature would exceed 125 °C without thermal enhancement. A 25 cm² copper pour (2 oz Cu) or small clip-on heatsink is mandatory for sustained 1.5 A operation at ambient >40 °C.

What capacitor types and values are mandatory for stability?

A 2.2 µF solid tantalum capacitor is required on the input (IN) pin, and a 1 µF solid tantalum capacitor on the output (OUT) pin. Aluminum electrolytic capacitors may be substituted only if rated ≥10× these values (22 µF and 10 µF respectively) and placed close to the device to avoid instability and oscillation.