onsemi MC79M08CDTG

Overview

MC79M08CDTG from onsemi is a fixed-output negative voltage regulator delivering −8.0 V at up to 500 mA, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation. It operates over 0 °C to +125 °C and uses a DPAK-3 surface-mount package with Pb-free finish, commonly deployed in industrial power supplies and analog circuitry requiring stable negative bias rails.

For engineers reviewing the MC79M08CDTG datasheet, pinout, applications, or equivalent options, key selection considerations include output voltage tolerance (±4.0%), dropout voltage (1.1 V), ripple rejection (63 dB at 120 Hz), thermal resistance (θ_JA = 92 °C/W), and compatibility with standard input/output capacitor values (0.33 µF and 1.0 µF).

Technical Context

The MC79M08CDTG implements a monolithic bipolar linear regulator architecture with integrated pass transistor, error amplifier, reference, and protection circuitry. Its design includes internal current limiting that activates before device damage, thermal shutdown triggered at ~150 °C junction temperature, and safe-area compensation to prevent secondary breakdown during overload.

It requires no external components for basic operation but benefits from input bypassing (0.33 µF) and output stabilization (1.0 µF). The regulator maintains regulation only when input voltage remains ≥1.1 V more negative than output - i.e., VI ≤ −9.1 V under nominal load - and exhibits 0.4 mV/°C average temperature coefficient over 0 °C to 125 °C.

Key Specifications

Pinout & Package

DPAK-3 (Case 369C) surface-mount package with exposed drain pad for thermal conduction; dimensions 6.10 mm × 6.54 mm × 2.28 mm, pitch 2.29 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7908CT and MC79M08BDTRKG, the MC79M08CDTG offers optimized cost and board area for commercial-temperature surface-mount applications, trading extended cold-temperature operation for tighter manufacturing tolerances and Pb-free compliance in a compact DPAK-3 form factor.

Availability

MC79M08CDTG is available at Aetrix Electronics and suitable for industrial power supplies, analog signal conditioning, embedded control systems, and test & measurement equipment requiring stable component supply and RoHS-compliant packaging.

Supply support for MC79M08CDTG 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, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The MC79M00 series was designed as a robust, drop-in negative complement to the MC78M00 positive regulator family, targeting cost-sensitive, high-reliability linear power applications in commercial and industrial environments.

FAQ

What is the maximum input voltage rating for the MC79M08CDTG?

The MC79M08CDTG has an absolute maximum input voltage of −35 V DC. Operation beyond this rating risks permanent damage. For reliable regulation, input must remain at least 1.1 V more negative than the output (i.e., VI ≤ −9.1 V), and typical operating range is −10.5 V to −25 V per datasheet test conditions. Exceeding −35 V violates maximum ratings and voids reliability guarantees.

Does the MC79M08CDTG require external capacitors to function properly?

Yes, the MC79M08CDTG requires an input capacitor (0.33 µF minimum) if located remotely from the main filter, and an output capacitor (1.0 µF minimum) to ensure stability and transient response. These values are specified in the standard application circuit. Omitting them may cause oscillation or poor load regulation, especially under dynamic current changes. Ceramic or tantalum types are acceptable per datasheet recommendations.

What is the thermal resistance and power dissipation limit of the MC79M08CDTG?

The MC79M08CDTG in DPAK-3 package has θ_JA = 92 °C/W and θ_JC = 6.0 °C/W. With internally limited power dissipation, its practical max power depends on ambient temperature and PCB copper area. At T_A = 50 °C, maximum continuous dissipation is ~0.55 W - corresponding to ~69 mA at full 1.1 V dropout or ~500 mA with adequate heatsinking. Derating is required above 50 °C ambient.

How does the MC79M08CDTG compare to the LM7908 in terms of pin compatibility and performance?

The MC79M08CDTG and LM7908 share identical electrical functionality (−8 V, 500 mA, thermal/short-circuit protection) and pinout order (Ground–Input–Output), but differ in package: MC79M08CDTG uses DPAK-3 (surface-mount), while LM7908CT uses TO-220 (through-hole). They are not mechanically interchangeable, though schematic symbols and net connections match. Thermal performance differs significantly due to package θ_JA (92 vs. 65 °C/W).

Is the MC79M08CDTG suitable for automotive applications?

The MC79M08CDTG is rated for 0 °C to +125 °C junction temperature, meeting commercial/industrial requirements but not AEC-Q100 automotive qualification. For automotive use, select the "B" grade variant MC79M08BDTRKG (−40 °C to +125 °C) - which shares identical electrical specs and DPAK-3 footprint - or verify qualification status directly with onsemi for specific vehicle subsystems.