Texas Instruments UC3544N

Overview

UC3544N 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 peak), programmable time delays, and a 2.5 V ±1% internal reference. It operates from 4.7 V to 40 V input supply and supports industrial temperature range (0°C to 70°C). It is used in regulated DC power supplies for fault-triggered shutdown and system-level protection.

For engineers reviewing the UC3544N datasheet, UC3544N pinout, UC3544N application, or UC3544N equivalent, key selection considerations include its dual-threshold voltage monitoring capability, independent comparator inputs enabling sub-2.5 V U.V. detection via reference division, SCR trigger timing behavior, and compatibility with external compensation for linear current-sense amplifier operation.

Technical Context

The UC3544N implements three independent analog monitoring paths: an over-voltage comparator with latch/reset capability and SCR trigger output; an under-voltage comparator with externally programmable delay; and a current-limit amplifier/comparator with offset adjustment and selectable gain mode. All comparators share the same 2.5 V reference but accept fully uncommitted inputs - enabling flexible threshold configuration using external resistor dividers.

Its SCR driver delivers up to 300 mA peak current with <500 ns propagation delay from O.V. input, while indicator outputs (O.V. Indicate, U.V. Indicate, C.L. Output) are open-collector and wire-or'able. The device supports remote activation and external reset, and its current-limit section can operate as either a high-gain comparator or a compensated linear amplifier with bandwidth of 5 MHz.

Key Specifications

Pinout & Package

UC3544N is packaged in 18-pin plastic dual in-line (PDIP-N) package per JEDEC MS-001, with 0.3-inch body width and through-hole mounting. 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 UC2544N, UC3544N offers lower cost and smaller footprint for commercial-temperature applications but sacrifices extended thermal range; versus TL7705ACD, UC3544N delivers comprehensive triple-monitoring capability at the expense of higher design complexity and BOM count.

Availability

UC3544N is available at Aetrix Electronics and suitable for industrial motor drives, telecom power modules, test equipment power validation, and PLC power supply protection requiring stable component supply across long production lifecycles.

Supply support for UC3544N 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, delivering analog, embedded processing, and digital signal processing technologies since 1930.

The UC3544N belongs to TI's legacy UCx54x family of power supply supervisory ICs, designed specifically for hardware-level fault detection and crowbar protection in regulated DC power systems where firmware-based monitoring is insufficiently robust.

FAQ

What is the maximum input voltage rating for UC3544N?

The UC3544N has an absolute maximum VIN rating of 40 V. Operation above this voltage risks permanent damage to internal circuitry, including the reference generator and SCR driver. For reliable long-term use, the recommended operating range is 4.7 V to 40 V, with derating advised near the upper limit depending on ambient temperature and power dissipation.

Does UC3544N support under-voltage monitoring of input AC lines?

Yes, UC3544N supports input line monitoring via its U.V. inputs. When configured with appropriate resistive divider and rectification, the U.V. comparator can detect AC line sags or brownouts by sampling the rectified and filtered input voltage. Figure 9 in the TI SLUS188A datasheet shows a validated implementation using a diode-capacitor network feeding the U.V. N.I. Input.

Can UC3544N be used to monitor voltages below 2.5 V?

Yes, UC3544N can monitor voltages below 2.5 V using its uncommitted comparator inputs. By connecting a resistor divider between the target sub-2.5 V rail and VREF, the divided voltage is compared against VREF at the O.V. or U.V. inputs - effectively scaling the threshold downward. This technique is explicitly supported in the UC1544/2544/3544 series and documented in the "Uncommitted Comparator Inputs" section of the datasheet.

What is the purpose of the Offset/Comp pin on UC3544N?

The Offset/Comp pin on UC3544N serves two roles: it accepts an external resistor to introduce fixed input offset voltage into the current-limit amplifier, and it provides the compensation node for configuring the amplifier as a stable linear circuit. When used with external RC networks, it enables precise gain setting and phase margin control - critical when implementing analog current limiting rather than simple comparator-based shutdown.

Is UC3544N pin-compatible with UC3543N?

No, UC3544N is not pin-compatible with UC3543N. UC3544N uses an 18-pin PDIP package with dedicated O.V. and U.V. inverting/non-inverting inputs, while UC3543N is a 16-pin variant lacking the uncommitted inputs and using internally connected VREF for one sensing path. Their pin functions differ significantly - for example, pins 15–18 on UC3544N have no counterparts on UC3543N.