Texas Instruments LM2578AMX/NOPB

Overview

LM2578AMX/NOPB from Texas Instruments is a monolithic switching regulator controller IC featuring an internal NPN output transistor, dual comparator inputs (inverting and non-inverting), 1.0 V reference, and oscillator programmable up to 100 kHz via single external capacitor. It supports buck, boost, and inverting DC-DC topologies with up to 750 mA output current, <0.9 V collector saturation voltage, and operates from 2 V to 40 V input supply. Used in industrial power supplies requiring compact, low-component-count voltage conversion.

For engineers reviewing the LM2578AMX/NOPB datasheet, LM2578AMX/NOPB pinout, LM2578AMX/NOPB application, or LM2578AMX/NOPB equivalent, key selection criteria include its 1.0 V reference accuracy, ground- or VIN-referenced current limit sensing, 90% max duty cycle, thermal shutdown, and SOIC-8 package compatibility with legacy LM2578A designs.

Technical Context

The LM2578AMX/NOPB integrates a precision 1.0 V reference into both comparator inputs, enabling direct feedback without external op-amps in inverting configurations. Its oscillator uses a single timing capacitor (e.g., 3900 pF for ~20 kHz) and includes blanking to enforce ≤90% duty cycle.

Current limiting operates cycle-by-cycle with 110 mV sense threshold referenced either to ground or VIN; emitter output must not fall below −1 V (−0.6 V at TJ ≥100°C), constraining negative-output designs to external transistor use. The output NPN transistor delivers up to 750 mA with VC(sat) ≤0.9 V at 750 mA pulsed and VE(sat) ≤2.0 V at 80 mA.

Key Specifications

Pinout & Package

LM2578AMX/NOPB is housed in an 8-pin SOIC package (Package Number D0008A), with exposed pad omitted. Thermal resistance θJA = 150°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar switching regulator controller applications.

Compared with LM2578AMX/NOPB, LM2578ADRE4 offers identical performance in alternate packaging, while UC3843BD1R2G trades integrated comparator flexibility for higher current drive and precision reference-making it preferable only where external compensation is acceptable and 1.0 V reference is not required.

Availability

LM2578AMX/NOPB is available at Aetrix Electronics and suitable for industrial DC power supplies, battery-powered boost converters, inverting polarity converters, and motor speed control drivers requiring stable component supply and long-term manufacturability.

Supply support for LM2578AMX/NOPB 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

Texas Instruments is a global semiconductor leader delivering analog, embedded processing, and logic solutions with emphasis on reliability, longevity, and industrial-grade qualification.

The LM2578A product line was designed as a cost-optimized, easy-to-use switching regulator controller for medium-power DC-DC conversion in industrial, instrumentation, and telecom infrastructure applications.

FAQ

What is the maximum allowable emitter voltage swing below ground for LM2578AMX/NOPB?

The LM2578AMX/NOPB emitter output must not be driven more than −1 V below ground at TJ < 100°C, and no more than −0.6 V below ground when junction temperature reaches or exceeds 100°C. Exceeding this violates absolute maximum ratings and risks unintended turn-on of the internal NPN transistor. For negative-output designs, an external PNP transistor is required to isolate the emitter node, as documented in TI's Figure 29 and Application Note SNVS767E.

Does LM2578AMX/NOPB support synchronization of multiple units?

Yes, LM2578AMX/NOPB supports external synchronization: applying a 1.5–2.0 V pulse waveform (≥2 μs width) to the oscillator timing pin (Pin 4) synchronizes multiple devices. Each unit requires its own timing capacitor, sized ~20% slower than the sync frequency. The sync signal source must drive capacitive loads and deliver up to 500 μA per LM2578AMX/NOPB, as specified in the Synchronizing Devices section of the SNVS767E datasheet.

What is the typical oscillator frequency for LM2578AMX/NOPB with a 3900 pF timing capacitor?

With a 3900 pF timing capacitor, LM2578AMX/NOPB achieves a typical oscillator frequency of 20 kHz, with a guaranteed range of 16–24 kHz across temperature and process variation. This value derives from the formula fOSC = 8×10⁻⁵ / CT (Hz), where CT is in farads. At 25°C, measured units center near 20 kHz; frequency drift is −0.13%/°C, resulting in ±1.3 kHz variation over −40°C to +85°C ambient.

Can LM2578AMX/NOPB be used in a buck-boost configuration?

No, LM2578AMX/NOPB is not suitable for true buck-boost (four-switch or SEPIC) topologies. It supports only buck, boost, and inverting configurations due to its single-NPN output stage and fixed internal logic. While the inverting configuration produces negative output from positive input, it lacks the dual-switch control needed for non-inverting buck-boost. For buck-boost applications, TI recommends alternatives such as the LM2596 or TPS5430, which provide dedicated control architectures.

What is the purpose of the dual comparator inputs (Pins 1 and 7) on LM2578AMX/NOPB?

The dual comparator inputs (Pin 1: inverting, Pin 7: non-inverting) on LM2578AMX/NOPB each feature an internal 1.0 V reference, enabling direct connection of feedback networks without external op-amps. This architecture simplifies inverting regulator designs-where output polarity reversal is inherent-and allows flexible error-sensing arrangements. Both inputs sink negligible current (<0.5 μA), preserving accuracy in high-impedance divider networks, as confirmed in the Electrical Characteristics table of SNVS767E.