STMicroelectronics L7905CD2T-TR

Overview

L7905CD2T-TR 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 operates with input voltages down to -35 V (for VO = -5 V), exhibits ±50 mV load regulation (250–750 mA), and maintains 100 µV RMS output noise (10 Hz–100 kHz) in D²PAK package - used for local regulation in split-supply industrial power rails and analog subsystems.

For engineers reviewing the L7905CD2T-TR datasheet, L7905CD2T-TR pinout, L7905CD2T-TR application, or L7905CD2T-TR equivalent, key selection criteria include dropout voltage (1.4 V @ 1 A), supply voltage rejection (54–60 dB @ 120 Hz), junction-to-case thermal resistance (3 °C/W), and compatibility with solid tantalum output capacitors per ST's stability requirements.

Technical Context

The L7905CD2T-TR implements a monolithic PNP-based series pass architecture with internal current limiting, thermal shutdown, and safe operating area (SOA) protection on the output transistor. Its feedback loop is internally compensated for stable operation with ≥1 µF solid tantalum output capacitance.

It functions as a standalone negative rail generator requiring no external components for basic operation, but supports adjustable output configurations via external resistive dividers. The device is specified for 0–125 °C junction temperature and requires heatsinking to sustain >1 A continuous output current.

Key Specifications

Pinout & Package

Package: D²PAK (TO-263), surface-mount, thermally enhanced plastic package with exposed drain pad for PCB heat transfer.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7905CT and MC7905BD2TG, the L7905CD2T-TR uniquely combines D²PAK thermal efficiency (3 °C/W R_thJC), integrated SOA protection, and ST's proven reliability in industrial ambient conditions - making it optimal for compact, high-reliability negative rail designs.

Availability

L7905CD2T-TR is available at Aetrix Electronics and suitable for industrial sensor conditioning, PLC analog I/O modules, legacy power retrofit, and embedded control board local regulation requiring stable component supply, long-lifecycle assurance, and RoHS-compliant packaging.

Supply support for L7905CD2T-TR 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 power management applications.

The L79xxC series was developed specifically for robust, cost-effective negative voltage regulation in industrial and embedded systems - emphasizing thermal resilience, fault protection, and compatibility with standard positive-regulator counterparts like the L78xx family.

FAQ

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

The L7905CD2T-TR requires a minimum input-to-output differential of 1.4 V (dropout voltage) to maintain regulation. For a -5 V output, this means the input must be ≤ -6.4 V DC. Absolute maximum input is -35 V, but practical design uses -7 V to -12 V to balance efficiency and ripple rejection.

Can aluminum electrolytic capacitors replace the recommended solid tantalum output capacitor?

Yes, but ST specifies that aluminum electrolytic capacitors must be at least ten times the value of the recommended solid tantalum capacitor (≥10 µF instead of ≥1 µF) and placed directly at the output pin. This compensates for higher ESR, which otherwise risks instability and oscillation in the feedback loop.

Does the L7905CD2T-TR require an input bypass capacitor?

Yes - an input capacitor (CI ≥ 2.2 µF solid tantalum) is required if the regulator is located more than ~2 inches from the main power supply filter. This prevents high-frequency noise injection and improves transient response during load steps, especially in distributed power architectures.

How does thermal performance differ between D²PAK and TO-220 packages for this regulator?

The D²PAK package offers R_thJC = 3 °C/W versus 5 °C/W for TO-220, enabling ~40% higher power dissipation before reaching thermal shutdown at the same heatsink temperature. This translates to sustained 1.5 A output in compact SMT layouts where TO-220 would require oversized external heatsinks.