STMicroelectronics L7908CV

Overview

L7908CV from STMicroelectronics is a fixed-output, three-terminal negative linear voltage regulator delivering -8 V at up to 1.5 A output current, featuring thermal overload protection, short-circuit protection, and SOA-controlled output transition. It operates with input voltages down to -35 V (for VO = -5 to -18 V), supports local on-card regulation in split-supply systems, and is widely used in industrial power supplies requiring stable dual-rail ±8 V operation.

For engineers reviewing the L7908CV datasheet, L7908CV pinout, L7908CV application, or L7908CV equivalent, key selection criteria include guaranteed -8 V output tolerance (±5%), dropout voltage of 1.1 V at 1 A, thermal resistance junction-to-case of 5 °C/W (TO-220), load regulation ≤160 mV, and compatibility with standard L78xx positive regulators for symmetrical supply design.

Technical Context

The L7908CV implements a monolithic PNP pass transistor architecture with internal current limiting, thermal shutdown, and safe operating area (SOA) protection-ensuring robustness under transient overloads and sustained short circuits. Its feedback loop maintains output stability with ≥54 dB supply voltage rejection at 120 Hz and ≤175 µV RMS output noise (10 Hz–100 kHz).

Designed for fixed-voltage operation, it accepts input voltages from -11.5 V to -23 V (typical operating range) and delivers regulated -8 V across junction temperatures from 0 °C to 125 °C. Output voltage drift is specified at -0.6 mV/°C, enabling predictable performance in temperature-varying environments without external compensation.

Key Specifications

Pinout & Package

Supplied in TO-220 package with standard 3-pin configuration: Pin 1 = Ground (GND), Pin 2 = Input (IN), Pin 3 = Output (OUT). The metal tab is electrically connected to the GND terminal and serves as thermal interface to heatsink.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM337T and MC7908CT, the L7908CV offers superior thermal resistance (5 °C/W), lower dropout (1.1 V), and tighter load regulation (160 mV), making it optimal for compact, thermally constrained industrial power modules requiring fixed -8 V with minimal external components.

Availability

L7908CV is available at Aetrix Electronics and suitable for industrial control systems, audio equipment, test instrumentation, and embedded power management requiring stable component supply and long-term lifecycle support.

Supply support for L7908CV 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 power regulation in industrial and embedded systems-emphasizing ruggedness, ease of use, and compatibility with the complementary L78xx positive regulator family.

FAQ

What is the minimum input voltage required for the L7908CV to regulate at -8 V?

The L7908CV requires the input voltage to be at least 1.1 V more negative than the output voltage under load. At 1 A output current and 25 °C, the dropout voltage is 1.1 V, so VI must be ≤ -9.1 V. For reliable operation across temperature and load, ST recommends VI ≤ -11.5 V minimum per datasheet conditions.

Can the L7908CV be used without a heatsink?

Yes, but only at very low output currents. With RthJA = 50 °C/W (TO-220), ambient temperature of 25 °C, and junction limit of 125 °C, maximum allowable power dissipation is ~2 W - corresponding to ~250 mA at 8 V drop. For >500 mA, a heatsink is mandatory to prevent thermal shutdown.

Is an input capacitor required for stable operation?

An input capacitor (CI ≥ 2.2 µF solid tantalum) is required if the regulator is located more than a few centimeters from the main power supply filter, per Figure 4 in the datasheet. It reduces high-frequency noise and prevents oscillation caused by trace inductance between bulk capacitance and the regulator input pin.

Does the L7908CV support adjustable output voltages?

While designed as a fixed -8 V regulator, the L7908CV can be configured for adjustable output using external resistors per Figure 6 in the datasheet. However, this modifies regulation accuracy, line/load regulation, and thermal behavior - ST does not characterize or guarantee performance in adjustable mode.