STMicroelectronics LM339QT

Overview

LM339QT from STMicroelectronics is a low-power quad voltage comparator in QFN16 3×3 mm package, designed for single-supply operation from +2 V to +36 V (or ±1 V to ±18 V dual supply), with ±1 mV typical input offset voltage, 25 nA typical input bias current, and 250 mV typical low-level output saturation voltage at 4 mA sink current - used in precision threshold detection, window comparators, and analog-to-digital interface circuits.

For engineers reviewing the LM339QT datasheet, LM339QT pinout, LM339QT application, or LM339QT equivalent, key selection considerations include input common-mode range extending to ground on single supply, TTL/CMOS-compatible open-collector outputs, 1.3 µs typical response time, and thermal resistance of 45 °C/W (junction-to-ambient) in QFN16 packaging.

Technical Context

The LM339QT integrates four independent PNP-input comparators with rail-to-rail differential input voltage capability up to ±36 V and common-mode input range from 0 V to (V_CC − 1.5 V), enabling direct ground-referenced sensing without level-shifting. Its open-collector outputs support wired-OR logic and mixed-voltage interfacing.

Designed for industrial and consumer systems requiring stable DC thresholds, it delivers 1.1 mA total supply current independent of V_CC, supports sink currents up to 16 mA per output, and maintains performance across 0 °C to +70 °C ambient temperature.

Key Specifications

Pinout & Package

LM339QT uses a 16-pin QFN (3 mm × 3 mm, 0.5 mm pitch) with exposed thermal pad (EP) for enhanced thermal dissipation. Pin 1 marked via top-side dot; pins numbered counterclockwise.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad voltage comparator applications.

Compared with LM339DT and TLV339IPW, the LM339QT offers optimal balance of wide supply range (+2 V to +36 V), compact QFN16 footprint, and industry-standard thermal performance - making it ideal for space-constrained industrial controls and multi-rail embedded systems where both voltage flexibility and board area matter.

Availability

LM339QT is available at Aetrix Electronics and suitable for overvoltage protection circuits, zero-crossing detection, temperature threshold alarms, and transducer signal conditioning requiring stable component supply across automotive, industrial control, and test equipment programs.

Supply support for LM339QT 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering intelligent power, sensing, connectivity, and microcontroller solutions for industrial, automotive, and consumer markets.

The LM339 series belongs to ST's precision analog comparators product line, engineered for robust DC threshold detection in harsh environments - emphasizing input accuracy, supply flexibility, and long-term stability over speed-optimized architectures.

FAQ

What is the maximum sink current per output of the LM339QT?

The LM339QT supports up to 16 mA sink current per output channel at V_O = 1.5 V and differential input voltage of 1 V, as specified in Table 3 of the datasheet. This rating holds across the full operating temperature range (0 °C to +70 °C) and enables direct driving of LEDs, relays, or logic inputs without external buffers.

Does the LM339QT require a negative supply to sense signals near ground?

No. The LM339QT's input common-mode voltage range includes 0 V on single supply, allowing direct connection of either input to ground or near-ground signals without level-shifting circuitry. This is enabled by its PNP input stage and is confirmed in Table 2 (VICM = 0 V minimum) and Figure 1 pin diagram.

Can the LM339QT outputs be wire-OR'd together?

Yes. All four outputs are open-collector NPN structures, enabling direct wired-OR connection to a shared pull-up resistor. This supports logic functions such as "any-of-four" alarm triggering or priority encoding without additional discrete components - verified in the Functional Description section and Typical Applications (Figures 8–21).

Is the exposed thermal pad (EP) of the QFN16 package electrically connected?

Yes. Pins 14, 15, and 16 of the LM339QT are internally shorted to the exposed thermal pad and substrate ground. The pad must be soldered to a PCB ground plane to meet thermal specifications (θ_JA = 45 °C/W) and ensure reliable operation - as documented in Section 6.3 and Figure 24 mechanical drawing.