STMicroelectronics L7815CT

Overview

L7815CT from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering +15 V output at up to 1.5 A, featuring thermal overload protection, short-circuit protection, and safe operating area (SOA) protection in a TO-220 package. It operates across an input voltage range of 17.5–30 V, maintains ±2% output tolerance (C-grade), and supports industrial temperature range (0 to 125 °C junction). It is used for local on-card regulation in power supplies for microcontroller-based control systems.

For engineers reviewing the L7815CT datasheet, L7815CT pinout, L7815CT application, or L7815CT equivalent, key selection considerations include dropout voltage (2 V @ 1 A), load regulation (≤300 mV over 5 mA–1.5 A), supply voltage rejection (55 dB @ 120 Hz), quiescent current (8 mA), and thermal resistance (R_thJA = 50 °C/W in TO-220).

Technical Context

The L7815CT implements a monolithic silicon voltage regulator with internal current limiting, thermal shutdown, and SOA protection-enabling robust operation without external protection circuitry. Its architecture relies on a PNP pass transistor controlled by an error amplifier referenced to a precision bandgap voltage source.

It requires minimum 5 mA load current for regulation stability and uses standard decoupling: 0.33 µF at input and 0.1 µF at output. Dropout behavior is defined at 2 V under full 1 A load at 25 °C, and output voltage drift is –1 mV/°C over temperature.

Key Specifications

Pinout & Package

The L7815CT is housed in a TO-220 package with vertical mounting orientation, metal tab electrically connected to the output terminal and thermally coupled to the die for heatsink attachment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7815CD2TR and MC7815CD2TG, the L7815CT offers superior supply rejection (55 dB vs. ≤50 dB), tighter load regulation (≤300 mV vs. ≥400 mV), and higher short-circuit current capability (0.35 A vs. ≤0.25 A), making it preferred for noise-sensitive and reliability-critical analog power domains.

Availability

L7815CT is available at Aetrix Electronics and suitable for industrial PLC power supplies, microcontroller board local regulation, DC motor driver auxiliary rails, and legacy instrumentation power modules requiring stable component supply and long-lifecycle support.

Supply support for L7815CT 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 analog, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The L78 series belongs to ST's legacy linear regulator product line, engineered for ruggedness and simplicity in fixed-voltage local regulation-targeting cost-effective, maintenance-free power conversion in embedded control and instrumentation.

FAQ

What is the minimum required input voltage for stable 15 V output from the L7815CT?

The L7815CT requires a minimum input voltage of 17.5 V DC to maintain regulation under full load (1.5 A) and maximum temperature (125 °C). This accounts for its 2 V dropout voltage and ensures output remains within 14.4–15.6 V tolerance. Below 17.5 V, output drops linearly with input, and regulation is lost.

Can the L7815CT be used without a heatsink?

At ≤100 mA load and ambient temperatures ≤40 °C, the L7815CT may operate without a heatsink in free air due to its TO-220 package R_thJA of 50 °C/W. However, at 1 A load, power dissipation reaches ~17 W (e.g., 24 V_IN → 15 V_OUT), requiring a heatsink to keep junction temperature below 125 °C-otherwise thermal shutdown will activate.

Does the L7815CT require input and output capacitors, and what values are recommended?

Yes-ST specifies a 0.33 µF ceramic capacitor on the input and a 0.1 µF ceramic capacitor on the output, placed as close as possible to the device pins. These prevent oscillation and improve transient response. Larger bulk capacitors (e.g., 10–100 µF electrolytic) may be added upstream/downstream for energy storage and low-frequency filtering, but the minimum ceramics are mandatory for stability.

How does the L7815CT behave during short-circuit conditions?

Under short-circuit, the L7815CT limits output current to ~0.35 A (C grade) and activates thermal shutdown if junction temperature exceeds ~165 °C. It does not latch off-recovery occurs automatically once temperature falls below the hysteresis threshold (~140 °C). Peak short-circuit current reaches 2.2 A briefly before limiting engages, supporting brief fault events without damage.