onsemi MC7924BT

Overview

MC7924BT from onsemi is a fixed-output negative voltage regulator delivering −24 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 stable output under input ripple up to −38 V with ≥2.0 V headroom.

For engineers reviewing the MC7924BT datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage (1.3 V at 1.0 A), output voltage tolerance (±4%), thermal resistance (θ_JC = 5.0 °C/W), ripple rejection (56 dB at 120 Hz), and TO−220 package compatibility with standard heatsinks.

Technical Context

The MC7924BT implements a monolithic bipolar pass transistor with integrated protection circuitry: thermal overload detection triggers shutdown at +150 °C, while current limiting caps output at ~1.8 A under short-circuit conditions. Safe-area compensation dynamically reduces short-circuit current as V_IN−V_OUT increases, preventing second breakdown.

Its internal bias network draws 4.6 mA typical input current and exhibits −1.0 mV/°C temperature coefficient over 0°C to +125°C. Output noise is 170 µV_RMS (10 Hz–100 kHz), and line/load regulation are specified across −27 V to −38 V input range and 5 mA–1.5 A load range.

Key Specifications

Pinout & Package

MC7924BT uses the TO−220 package (Case 221AB), with heatsink surface electrically connected to Pin 2 (Input). The package is lead-free (G-suffix compliant) and rated for infinite heatsink mounting or free-air operation with θ_JA = 65 °C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC7924CTG, MC7924BT provides guaranteed operation down to −40°C - critical for outdoor telecom or automotive engine-control modules. Versus LM337T, MC7924BT eliminates resistor networks and delivers better thermal performance (5.0 vs. 6.5 °C/W θ_JC) at fixed −24 V.

Availability

MC7924BT is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, legacy telecom line card bias, and operational amplifier dual supply applications requiring stable component supply with long lifecycle support.

Supply support for MC7924BT 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 manufacturer specializing in energy-efficient power management, analog, and sensing solutions for automotive, industrial, and cloud infrastructure markets.

The MC7900 series - including MC7924BT - was designed as a rugged, drop-in complement to the MC7800 positive regulator family, targeting industrial power supplies, analog instrumentation, and legacy logic systems requiring fixed negative rails.

FAQ

What is the maximum input voltage rating for the MC7924BT?

The MC7924BT supports a maximum input voltage of −40 V DC under all operating conditions. This rating is defined in the Absolute Maximum Ratings table and applies across the full −40°C to +125°C junction temperature range. Exceeding −40 V risks permanent damage to the internal pass transistor and protection circuitry.

Does the MC7924BT require input and output capacitors for stable operation?

Yes - while the MC7924BT operates without external components in ideal lab conditions, onsemi recommends a 0.33 µF input capacitor (tantalum or low-ESR ceramic) and a 1.0 µF output capacitor (tantalum or aluminum electrolytic) for production designs. These capacitors suppress high-frequency instability and improve transient response, especially with long PCB traces or large load capacitance.

How does the MC7924BT handle short-circuit conditions?

The MC7924BT employs internal short-circuit current limiting that restricts output current to approximately 1.8 A during sustained output shorts. Combined with thermal shutdown at +150°C junction temperature, this dual-protection scheme prevents device destruction and allows automatic recovery once the fault is removed and temperature drops below the hysteresis threshold.

Can the MC7924BT be used in parallel to increase output current?

No - the MC7924BT is not designed for parallel operation. Its output voltage tolerance (±4%) and lack of current-sharing features mean paralleling units will cause unequal current distribution, thermal runaway, and premature failure. For >1.0 A requirements, use a single higher-current regulator or add an external pass transistor per Figure 9 in the datasheet.

What is the purpose of the heatsink connection on Pin 2 of the MC7924BT?

Pin 2 (Input) of the MC7924BT is internally connected to the metal tab/heatsink surface. This design allows direct mechanical and thermal attachment to a heatsink while electrically referencing the input rail. When mounting, ensure electrical isolation (e.g., mica washer + thermal paste) if the heatsink is grounded or at a different potential than the input supply.