STMicroelectronics LM239QT

Overview

LM239QT 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), featuring ±1 mV typical input offset voltage, 25 nA typical input bias current, and 250 mV typical 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 LM239QT datasheet, LM239QT pinout, LM239QT application, or LM239QT equivalent, key selection considerations include input common-mode range extending to ground on single supply, TTL/CMOS-compatible open-collector outputs, thermal resistance of 45 °C/W (junction-to-ambient), and guaranteed operation from –40 °C to +105 °C.

Technical Context

The LM239QT implements four independent PNP-input comparators with rail-to-rail differential input voltage capability up to ±36 V and common-mode input range from ground to (V_CC+ – 1.5 V). Its input stage draws constant reverse-biased current, eliminating reference-line loading effects.

Each comparator delivers open-collector output capable of sinking ≥6 mA at 1.5 V output, with 1.3 μs typical response time (100 mV step, 5 mV overdrive) and <300 ns large-signal propagation delay under TTL-level conditions. Supply current remains stable at 1.1 mA across full voltage range.

Key Specifications

Pinout & Package

LM239QT uses a 16-pin QFN (3 mm × 3 mm, 0.5 mm pitch) with exposed thermal pad (EP) for enhanced thermal performance. Pin 1 marked by dot; pins numbered counterclockwise from top-left corner when viewed top-down.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM239QT, TLV331QPWR offers 94% lower quiescent current but lacks integrated quad functionality and thermal performance; LM339DT provides identical electrical behavior but sacrifices thermal efficiency and extended temperature support-making LM239QT optimal for space-constrained, high-reliability industrial designs.

Availability

LM239QT is available at Aetrix Electronics and suitable for overvoltage protection circuits, temperature threshold monitors, zero-crossing detectors, and sensor signal validation systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM239QT 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, and control solutions for automotive, industrial, and consumer markets.

The LM239QT belongs to ST's precision analog comparator family, engineered for robust performance in harsh industrial environments where ground-referenced sensing, wide supply tolerance, and long-term stability are critical.

FAQ

Can LM239QT operate from a single 3.3 V supply?

Yes. The LM239QT supports single-supply operation from +2 V to +36 V. At 3.3 V, it maintains full functionality: input common-mode range spans 0 V to 1.8 V, output sink current remains ≥4 mA, and propagation delay increases only marginally to ~1.8 μs-verified per Table 3 and Figure 7 in the official datasheet.

Is the exposed thermal pad (EP) electrically connected internally?

Yes. The exposed pad (pins 15–16) is internally connected to GND. ST's datasheet (Section 6.3, page 15) specifies that the EP must be soldered to a PCB GND plane to achieve the rated θ_JA of 45 °C/W; leaving it floating degrades thermal performance by >30 °C/W and risks parametric drift.

Does LM239QT support dual-supply operation with ±15 V?

Yes. Absolute maximum ratings specify ±18 V dual supply, and electrical characteristics (Table 2) confirm operation at ±1 V to ±16 V. With ±15 V, input common-mode range extends from –16.5 V to +13.5 V, and output saturation voltage remains ≤700 mV at 4 mA sink-enabling bipolar signal comparison in test equipment and audio level detectors.

What is the maximum capacitive load the output can drive without oscillation?

The LM239QT output is not internally compensated for capacitive loads. Datasheet Figure 5 shows stable operation up to 100 pF with 5.1 kΩ pull-up; beyond that, ringing occurs. For >100 pF (e.g., long traces or optocoupler inputs), add a 100 Ω series resistor adjacent to the output pin to isolate capacitance and maintain monotonic switching.