Texas Instruments LM239AD

Overview

LM239AD from STMicroelectronics is a low-power quad voltage comparator designed for precision threshold detection in industrial and embedded systems. It operates from single supplies (2–36 V) or dual supplies (±1 V to ±18 V), features ±1 mV typical input offset voltage, 25 nA typical input bias current, and rail-to-rail input common-mode range including ground - enabling direct sensing of signals referenced to system ground. It drives TTL, CMOS, and MOS logic loads with 250 mV typical output saturation voltage at 4 mA sink current.

For engineers reviewing the LM239AD datasheet, LM239AD pinout, LM239AD application, or LM239AD equivalent, key selection considerations include its guaranteed operation over –40 °C to +105 °C, low 1.1 mA supply current independent of supply voltage, compatibility with legacy SO14 PCB footprints, and absence of internal pull-ups requiring external termination for open-collector outputs.

Technical Context

The LM239AD uses a PNP-input stage enabling input common-mode voltage down to ground on single-supply operation - a critical feature for sensor interface and battery-monitoring circuits where reference points are grounded. Its open-collector outputs require external pull-up resistors and support mixed-voltage interfacing across TTL, CMOS, ECL, and MOS families.

It delivers 1.3 μs typical response time with 100 mV input step and 5 mV overdrive, and maintains stable performance across supply voltages from 2 V to 30 V without supply-current drift. Input offset voltage remains ≤2 mV maximum across temperature for the 'A' grade, supporting precision window and zero-crossing detection.

Key Specifications

Pinout & Package

LM239AD is packaged in SO14 (plastic micropackage), a 14-lead small outline integrated circuit with 1.27 mm pitch, compliant with JEDEC MS-012 and ECOPACK® environmental standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM339DR, LM239AD offers tighter offset and extended temperature range for harsh environments; compared with TLV339IPW, it supports higher supply voltages and legacy SO14 footprints but consumes more current - making LM239AD optimal for industrial 24 V systems needing proven reliability and layout continuity.

Availability

LM239AD is available at Aetrix Electronics and suitable for industrial motor control, automotive body electronics, and programmable logic controller (PLC) I/O modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM239AD 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, specializing in automotive, industrial, and power management ICs with vertical manufacturing and broad analog portfolio coverage.

The LM239AD belongs to ST's legacy precision analog comparator family, engineered for robust performance in industrial automation, power conversion, and safety-critical monitoring where long-term parametric stability and wide supply tolerance are mandatory.

FAQ

Does LM239AD support dual-supply operation?

Yes, LM239AD operates from dual supplies ranging from ±1 V to ±18 V. The device's input common-mode range extends to within 1.5 V of either rail, and its PNP input stage allows proper function with negative references. GND pin serves as the reference node, not a mandatory ground connection - enabling true split-rail configuration with VCC connected to V+ and GND tied to V−.

What is the maximum sink current per output, and is it safe to short-circuit to ground?

Each LM239AD output can safely sink up to 16 mA continuously, with absolute maximum rating of ~20 mA. Short-circuiting an output to ground is permitted per datasheet, but sustained short-circuit operation causes junction heating - thermal resistance (R_thJA) is 105 °C/W in SO14, so continuous 16 mA at 30 V supply would exceed safe junction temperature without heatsinking. Use current-limiting resistors or intermittent duty cycles for robust design.

Can LM239AD drive CMOS logic directly without a pull-up resistor?

No - LM239AD has open-collector outputs and cannot source current. A pull-up resistor to VCC (or another logic rail) is mandatory to establish a valid high logic level. Typical values range from 1 kΩ (for fast rise time with heavy loads) to 10 kΩ (for low power with light CMOS loads). Pull-up voltage may differ from VCC (e.g., 3.3 V pull-up with 5 V VCC), enabling mixed-voltage interfacing.

How does input bias current direction affect circuit design?

LM239AD's PNP input stage draws bias current *out* of both inputs (25 nA typ), meaning external resistors feeding the inputs must sink this current. This avoids loading errors in high-impedance voltage dividers and eliminates the need for balancing resistors - unlike NPN-input comparators where bias current flows *into* inputs and requires matched impedances to cancel offset. Designers should ensure source impedance is ≤100 kΩ to limit voltage error to <2.5 mV.