Texas Instruments UC3543N

Overview

UC3543N from Texas Instruments is a monolithic power supply supervisory IC integrating over-voltage (O.V.), under-voltage (U.V.), and current-limit (C.L.) sensing circuits with open-collector indicator outputs, SCR crowbar drive (300 mA), and an internal 2.5 V ±1% reference. It operates from 4.7 V to 40 V input, supports programmable time delays via external capacitors, and is rated for 0°C to 70°C ambient operation in PDIP-16 packaging. It is used in regulated DC power supplies to initiate fault shutdown before damage occurs.

For engineers reviewing the UC3543N datasheet, UC3543N pinout, UC3543N application, or UC3543N equivalent, key selection considerations include its dual-threshold voltage monitoring capability, independent open-collector outputs for O.V./U.V./C.L., SCR trigger timing behavior, remote activation/reset interface, and compatibility with 2.5 V reference-based sensing networks.

Technical Context

The UC3543N implements three independent comparator channels - one for over-voltage (non-inverting input tied to VREF), one for under-voltage (inverting input tied to VREF), and one for current limiting (fully uncommitted op-amp/comparator) - each with externally programmable delay via capacitor-to-ground connections. All comparators feature 25 mV hysteresis and operate with input bias currents below 1 µA.

Its SCR trigger output delivers up to –300 mA peak sink current at VIN = 5 V with <500 ns propagation delay from O.V. input transition; the trigger may be activated by any comparator output or external signal. The internal 2.5 V reference exhibits ±1% initial accuracy, 50 ppm/°C temperature stability, and supports load currents up to 10 mA without external trimming.

Key Specifications

Pinout & Package

UC3543N is supplied in a 16-pin plastic dual in-line package (PDIP-16), with 0.3-inch body width and standard through-hole footprint compatible with JEDEC MS-001. Pin 1 is bottom-left corner when notch faces up.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power supply supervisory applications.

Compared with UC2543N and TL7705ACD, the UC3543N uniquely combines triple-fault supervision, 0–40 V input flexibility, and integrated SCR drive in a single PDIP-16 package-making it irreplaceable in designs requiring coordinated O.V./U.V./C.L. response with hardware-level crowbar protection.

Availability

UC3543N is available at Aetrix Electronics and suitable for industrial motor drives, telecom line cards, medical diagnostic equipment, and DC power supply protection requiring stable component supply across long production lifecycles.

Supply support for UC3543N 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 company headquartered in Dallas, Texas, designing and manufacturing analog, embedded processing, and digital signal processing technologies since 1930.

The UC3543N belongs to TI's UCx54x family of monolithic power supply supervisory circuits, developed specifically for hardware-level fault detection and crowbar-triggered shutdown in regulated DC power systems.

FAQ

What is the maximum input voltage the UC3543N can withstand on its VIN pin?

The UC3543N has an absolute maximum VIN rating of 40 V. Operation beyond this voltage risks permanent damage to internal circuitry, including the reference generator and comparator input stages. For reliable long-term use, design should maintain VIN ≤ 40 V with appropriate derating for transients and ripple, especially when driving the SCR trigger output at high current.

Can the UC3543N monitor voltages below 2.5 V without external components?

No - the UC3543N does not support sub-2.5 V monitoring natively. Unlike the UC3544 variant, the UC3543N lacks uncommitted comparator inputs; its O.V. and U.V. comparators are hardwired to the internal 2.5 V reference. To monitor voltages below 2.5 V, external resistor dividers must scale the target voltage upward to match the 2.5 V threshold.

Does the UC3543N provide latch functionality for over-voltage faults?

Yes - the UC3543N includes optional over-voltage latching. When enabled via external RC network on the O.V. DELAY pin and proper configuration of the RESET pin, the O.V. IND output remains asserted after fault clearance until an active-low pulse is applied to the RESET terminal, ensuring persistent fault indication until deliberate system reset.

What is the purpose of the OFFSET/COMP pin on the UC3543N?

OFFSET/COMP serves two roles: (1) it adjusts input offset voltage of the current-limit amplifier to compensate for shunt resistor tolerance and PCB layout errors; (2) it provides a compensation node for stabilizing the C.L. amplifier when used in linear mode, preventing oscillation by allowing external capacitor placement between this pin and ground or output.

Is the UC3543N pin-compatible with the UC3544N?

No - the UC3543N (16-pin PDIP) is not pin-compatible with the UC3544N (18-pin PDIP). The UC3544N adds two dedicated uncommitted comparator inputs (U.V. N.I. IN and U.V. INV. IN) and reassigns several pins, resulting in different pin counts and incompatible layouts. Migration requires PCB redesign and updated schematic connectivity.