Texas Instruments LM3578AN/NOPB

Overview

LM3578AN/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 a 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. It is used in industrial power supplies requiring stable mid-current regulation at 0°C to +70°C ambient.

For engineers reviewing the LM3578AN/NOPB datasheet, LM3578AN/NOPB pinout, LM3578AN/NOPB application, or LM3578AN/NOPB equivalent, key selection criteria include its ground- or VIN-referenced current limit sense (110 mV threshold), duty cycle adjustability up to 90%, thermal shutdown, and compatibility with discrete external pass transistors for higher output current.

Technical Context

The LM3578AN/NOPB integrates a precision 1.0 V reference applied independently to both comparator inputs, enabling direct feedback without external op-amps in inverting configurations. Its oscillator uses a single timing capacitor (CT) to set frequency from <1 Hz to 100 kHz, with built-in blanking to enforce ≤90% maximum duty cycle.

The output stage is a high-voltage NPN transistor with collector-emitter sustaining voltage of 60 V and emitter swing limited to −1 V (−0.6 V above 100°C junction). Current limiting operates cycle-by-cycle using a 110 mV sense threshold referenced either to ground or VIN, with bias currents of 4.0 μA (VIN-referenced) or 0.4 μA (ground-referenced).

Key Specifications

Pinout & Package

LM3578AN/NOPB is housed in an 8-pin plastic DIP (PDIP) package (Package Number P0008E), with through-hole mounting and 0.3-inch body width. Thermal resistance is 95°C/W (junction-to-ambient).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3578AN/NOPB, LM2578AN/NOPB offers broader temperature capability and higher voltage ratings for harsher environments, while MC34063AP trades topology flexibility for integration density and lower BOM count in basic DC-DC applications.

Availability

LM3578AN/NOPB is available at Aetrix Electronics and suitable for industrial power supplies, sensor interface circuits, and embedded motor control systems requiring stable component supply and long-term manufacturability.

Supply support for LM3578AN/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 specializing in analog, embedded processing, and power management technologies, with decades of heritage in high-reliability power IC design.

The LM3578A series was developed as a flexible, topology-agnostic switching regulator controller targeting cost-effective, discrete-based DC-DC solutions for commercial industrial equipment where programmability and dual feedback inputs add design value.

FAQ

What is the maximum allowable emitter voltage swing below ground for LM3578AN/NOPB?

The LM3578AN/NOPB emitter output must not fall more than −1 V below ground at any time. At junction temperatures ≥100°C, this limit tightens to −0.6 V to prevent unintended turn-on of the internal NPN transistor. Exceeding these limits risks latch-up or excessive power dissipation in the output stage. Always verify emitter voltage during startup, transient load steps, and discontinuous conduction mode operation in inverting or buck configurations.

Can LM3578AN/NOPB be used in a synchronous rectifier configuration?

No, LM3578AN/NOPB does not support synchronous rectification. It features a single NPN output transistor with collector and emitter terminals exposed for external switching, but lacks complementary drive outputs, dead-time control, or gate-drive capability required for synchronous FETs. For synchronous designs, consider dedicated controllers like the TPS40200 or LM5116. LM3578AN/NOPB requires external Schottky or fast-recovery diodes in buck/boost/inverting topologies.

How is the oscillator frequency set for LM3578AN/NOPB, and what is the recommended capacitor tolerance?

The LM3578AN/NOPB oscillator frequency is set by a single external capacitor (CT) connected between Pin 4 and ground, following fOSC ≈ 8×10⁻⁵/CT (Hz). For example, 3900 pF yields ~20.5 kHz. TI recommends ±5% tolerance NP0/C0G ceramic capacitors to maintain frequency stability over temperature and voltage. Avoid X7R or Y5V types due to capacitance drift, which directly impacts regulation accuracy and EMI profile.

Does LM3578AN/NOPB support remote shutdown, and how is it implemented?

Yes, LM3578AN/NOPB supports remote shutdown by sinking additional current from the non-inverting input (Pin 7) relative to the inverting input (Pin 1). When the current into Pin 7 exceeds that into Pin 1 by >0.5 μA, the output disables. A common method uses a transistor switch pulling Pin 7 to ground through a 10 kΩ resistor. This feature enables system-level power sequencing and fault interlocks without modifying the main feedback loop of the LM3578AN/NOPB.

What is the purpose of the dual comparator inputs (Pins 1 and 7) on LM3578AN/NOPB?

The dual comparator inputs (Pin 1: inverting, Pin 7: non-inverting) each have an internal 1.0 V reference, enabling direct connection of feedback dividers without level-shifting op-amps. This architecture allows native implementation of inverting regulators (using Pin 6 as output emitter), buck-boost topologies, and differential sensing schemes. Unlike single-input controllers, LM3578AN/NOPB eliminates external amplifiers in polarity-inverting applications - reducing component count, board space, and potential error sources in the feedback path.