Microchip Technology LDTS24A

Overview

LDTS24A from Microsemi is a unidirectional heavy-duty transient voltage suppressor (TVS) designed for automotive load-dump protection in 24 V systems capable of withstanding double-voltage jump-start conditions. It features a 24.0 V reverse standoff voltage (V_WM), 26.5 V minimum breakdown voltage (V_BR @ 20 mA), 39.0 V maximum clamping voltage (V_C @ 77.0 A), 3000 W peak pulse power (50 ms), and operates from –50 °C to +175 °C - deployed across alternator-regulated vehicle power rails.

For engineers reviewing the LDTS24A datasheet, LDTS24A pinout, LDTS24A application, or LDTS24A equivalent, key selection criteria include its TO-3 hermetic package thermal performance (R_θJC < 1 °C/W), low clamping ratio (V_C/V_BR ≈ 1.47), polarity-specific anode-to-case configuration, and compliance with SAE J1128 and ISO 7637-2 load-dump waveform requirements.

Technical Context

The LDTS24A is engineered specifically for sustained high-energy transients arising from battery disconnection during alternator operation - a condition generating up to 120 V/100 ms pulses per ISO 7637-2 Pulse 5a. Its design prioritizes thermal robustness over fast response, leveraging bulk silicon geometry and hermetic TO-3 packaging to dissipate 50 W steady-state power at T_C = 25 °C and survive repeated 77 A, 8.3 ms surges.

Unlike standard TVS diodes rated for 1 kW/10/1000 µs waveforms, the LDTS24A's 3000 W rating applies to a 50 ms pulse width (Figure 1), reflecting its role in absorbing prolonged field-decay energy. Its anode-to-case polarity mandates mechanical mounting to chassis ground, and its 100 µA max reverse leakage at V_WM ensures minimal quiescent current draw in always-on vehicle modules.

Key Specifications

Pinout & Package

Hermetically sealed TO-3 (TO-204AD) package with two .052 inch diameter axial leads: anode connected internally to the metal case, cathode as the isolated lead. Mounting requires insulating hardware if case cannot be grounded.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar heavy-duty automotive transient suppression applications.

Compared with SMCJ24A, LDTS24A delivers superior thermal management and 50 ms pulse compliance essential for primary load-dump defense; versus LDTS24, it provides a 4.0 V lower clamping voltage at rated current - a critical margin improvement for 36 V-rated power stages.

Availability

LDTS24A is available at Aetrix Electronics and suitable for automotive ECU protection, commercial vehicle telematics, off-highway equipment power conditioning, and industrial battery-backed control systems requiring stable component supply across extended product lifecycles.

Supply support for LDTS24A 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

Microsemi (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability analog, RF, and radiation-hardened components for aerospace, defense, and automotive markets.

The LDTS series was developed by Microsemi's Scottsdale Division specifically for automotive load-dump and field-decay transient suppression in harsh under-hood environments - emphasizing hermetic packaging, extreme temperature resilience, and sustained high-power dissipation.

FAQ

What is the clamping voltage of LDTS24A at its rated surge current?

The LDTS24A has a maximum clamping voltage (V_C) of 39.0 V when subjected to its rated 77.0 A surge current (8.3 ms waveform). This value is measured per Figure 2 test conditions and reflects the peak voltage seen by downstream circuitry during worst-case load-dump events. The 39.0 V clamping enables safe operation of 36 V-tolerant power management ICs without additional series impedance or staged protection.

Is LDTS24A compatible with ISO 7637-2 Pulse 5a testing?

Yes, LDTS24A is explicitly designed for ISO 7637-2 Pulse 5a (load-dump) compliance. Its 3000 W rating at 50 ms pulse width aligns with the energy profile of this standardized 120 V/100 ms transient. Microsemi's datasheet confirms validation against this waveform, and the device's thermal design supports repeated exposure without parameter shift - making LDTS24A suitable as a primary protection element in certified automotive modules.

How should LDTS24A be mounted mechanically for optimal performance?

LDTS24A must be mounted with its metal case (anode) directly to a clean, unpainted chassis ground plane using appropriate hardware. This establishes the lowest possible inductance path for surge current and maximizes thermal transfer. Insulating washers or sleeves are required only if electrical isolation from chassis is mandated elsewhere in the system. The cathode lead connects to the protected 24 V line, and routing should minimize loop area to reduce EMI coupling.

What is the difference between LDTS24A and LDTS24?

The LDTS24A and LDTS24 share identical V_WM (24.0 V) and V_BR (26.5 V), but differ in clamping performance: LDTS24A clamps at 39.0 V @ 77.0 A, while LDTS24 clamps at 43.0 V @ 70.0 A. This 4.0 V reduction improves system margin for 36 V-rated components. Both use the same TO-3 package and thermal specs, and both are rated for 3000 W/50 ms - making LDTS24A the preferred choice where tighter voltage control is critical.

Does LDTS24A require a heatsink beyond the chassis mount?

No additional heatsink is required for LDTS24A when mounted to a thermally adequate chassis surface. Its junction-to-case thermal resistance is <1 °C/W, and its 50 W steady-state power dissipation rating assumes case temperature (T_C) is maintained at 25 °C via chassis conduction. In practice, mounting to ≥100 cm² of 2 mm thick aluminum or steel provides sufficient thermal mass for continuous operation - verified in Microsemi's thermal characterization (Figure 3).