onsemi MC7912ACT

Overview

MC7912ACT from onsemi is a fixed-output negative voltage regulator delivering −12 V at up to 1.0 A, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation for rugged operation in industrial power supplies. It requires no external components for basic regulation and maintains output stability across input ripple and load transients.

For engineers reviewing the MC7912ACT datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed −12 V output tolerance (±2%), dropout voltage of 1.3 V at 1.0 A, thermal resistance of 5.0 °C/W (junction-to-case), and TO-220 package compatibility with standard heatsinking solutions.

Technical Context

The MC7912ACT implements a monolithic bipolar pass transistor with integrated protection circuitry: thermal overload detection triggers shutdown before junction temperature exceeds +150 °C, while current limiting caps peak output current under short-circuit conditions. Safe-area compensation dynamically reduces short-circuit current as V_IN−V_OUT increases, preventing secondary breakdown.

Its internal bias network draws 4.4 mA typical input current and delivers ripple rejection of 61 dB at 120 Hz. Output noise is 75 µV_RMS (10 Hz–100 kHz), and line/load regulation are specified at ±240 mV max over full operating conditions - enabling stable dual-rail op-amp supplies and MECL-compatible negative rails.

Key Specifications

Pinout & Package

MC7912ACT is housed in a TO-220 package (Case 221AB), with heatsink surface electrically connected to Pin 2 (Input). The package supports through-hole mounting and direct thermal coupling to external heatsinks.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC7912CTG, MC7912ACT offers tighter 2% output tolerance critical for precision analog rails; versus LM337T, it eliminates resistor selection errors and layout sensitivity while trading off adjustability and ultimate ripple suppression.

Availability

MC7912ACT is available at Aetrix Electronics and suitable for industrial control systems, analog instrumentation, dual-rail op-amp designs, and legacy equipment repair requiring stable component supply and long-term lifecycle support.

Supply support for MC7912ACT 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, and sensor solutions for automotive, industrial, and cloud infrastructure markets.

The MC7900 Series was designed specifically to provide robust, drop-in negative voltage regulation complementary to the MC7800 positive series - targeting reliability-critical analog and mixed-signal power domains.

FAQ

What is the maximum input voltage rating for MC7912ACT?

The MC7912ACT supports a maximum input voltage of −35 V for output voltages between −5.0 V and −18 V, and −40 V for −24 V output variants. For MC7912ACT specifically (−12 V output), the absolute maximum input is −35 V DC. Exceeding this risks permanent device failure due to junction breakdown.

Does MC7912ACT require input and output capacitors for stable operation?

Yes - while the MC7912ACT functions without external capacitors in minimal configurations, onsemi recommends a 0.33 µF input bypass capacitor (tantalum or low-ESR ceramic) and a 1.0 µF output capacitor for stability, especially with long input traces or large load capacitance. These prevent oscillation and improve transient response.

Can MC7912ACT be used in parallel to increase output current?

No - the MC7912ACT is not designed for parallel operation. Its output voltage tolerance and thermal characteristics prevent balanced current sharing. To achieve >1.0 A, use an external boost transistor configuration as shown in Figure 9 of the datasheet, with proper heatsinking and current-limiting resistors.

What is the thermal resistance and power dissipation limit of MC7912ACT?

The MC7912ACT has a junction-to-case thermal resistance (θ_JC) of 5.0 °C/W. With no heatsink, its junction-to-ambient (θ_JA) is 65 °C/W. Maximum power dissipation is internally limited but typically capped at 15 W with appropriate heatsinking - corresponding to ~1.25 A at 12 V differential under +25°C ambient.

Is MC7912ACT pin-compatible with older MC7912 variants?

Yes - MC7912ACT uses the standard TO-220 (Case 221AB) package with identical pinout (Pin 1: Ground, Pin 2: Input, Pin 3: Output) and mechanical footprint as legacy MC7912B, MC7912C, and MC7912T devices. No PCB changes are needed for drop-in replacement in existing designs.