Texas Instruments LM361M

Overview

LM361M from Texas Instruments (formerly National Semiconductor) is a high-speed differential voltage comparator with complementary TTL outputs, 20 ns max propagation delay, ±15 V dual-supply operation, and 1 mV typical input offset voltage. It serves as a pin-for-pin replacement for SE529/NE529 in zero-crossing detection and flash analog-to-digital converter front-ends.

For engineers reviewing the LM361M datasheet, LM361M pinout, LM361M application, or LM361M equivalent, key selection criteria include guaranteed 20 ns max delay, tight output skew (≤5 ns), strobe-controlled output enable/disable, ±6 V common-mode input range, and compatibility with op-amp supply rails.

Technical Context

The LM361M implements a bipolar differential pair input stage optimized for speed and low input offset, with separate V+, V−, and VCC supplies enabling independent analog reference and TTL logic domain control. Its strobe input allows synchronous output gating without affecting internal comparator dynamics.

Complementary TTL outputs (OUTA and OUTB) are actively driven with matched propagation delays (tpd(0) and tpd(1) both ≤20 ns), and delay skew between outputs is specified at ≤5 ns over temperature. The device operates across 0°C to +70°C and supports ±5 V differential input swing within ±6 V common-mode range.

Key Specifications

Pinout & Package

LM361M is supplied in a 14-pin molded Dual-In-Line Package (NS Package Number M14A), 0.300-inch wide body, with standard through-hole mounting footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed differential comparator applications.

Compared with LM361N and LM161H, the LM361M offers commercial-temperature performance in a space-saving 0.300-inch DIP package-ideal for cost-sensitive, volume production of disk drive controllers and industrial data acquisition systems where military specs are unnecessary.

Availability

LM361M is available at Aetrix Electronics and suitable for disk drive servo systems, flash ADC subsystems, high-speed PWM controllers, and industrial motor phase detection requiring stable component supply and long-term obsolescence management.

Supply support for LM361M 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 acquired National Semiconductor in 2011 and maintains its high-performance analog product lines, including legacy comparators, with full datasheet, reliability, and cross-reference support.

The LM361M belongs to National Semiconductor's high-speed comparator family, designed specifically for timing-critical analog-to-digital conversion, zero-crossing detection, and strobed decision circuitry in storage and instrumentation systems.

FAQ

What is the maximum operating temperature range for the LM361M?

The LM361M is rated for 0°C to +70°C ambient operation, per its commercial-grade specification. This distinguishes it from the LM161 (−55°C to +125°C) and LM361H (−55°C to +125°C, military). For designs requiring extended temperature capability, LM361M is not suitable; consider LM161H instead. All thermal limits assume proper PCB copper area and airflow per National Semiconductor AN-450 guidelines. LM361M remains fully functional within its specified range without derating.

Does the LM361M require external pull-up resistors on its TTL outputs?

No, the LM361M features actively driven complementary TTL outputs (OUTA and OUTB) that source ≥2.4 V at −0.5 mA and sink ≤0.4 V at 6.4 mA-fully compliant with standard TTL logic levels without external pull-ups. This eliminates board space and timing uncertainty associated with passive termination. The outputs are designed for direct connection to 74LS or 74F-series inputs. LM361M's output drive strength is verified across temperature and supply variations per DS005708 Section 2.

Can the LM361M operate from a single +5 V supply?

No, the LM361M requires three independent supply connections: V+ (positive analog), V− (negative analog), and VCC (TTL logic). It cannot function on a single +5 V rail. Minimum valid configuration is V+ = +5 V, V− = −6 V, VCC = 4.75 V. Attempting single-supply operation will result in undefined output states and potential damage if input common-mode exceeds V− + 0.3 V. LM361M's architecture is inherently dual-supply; no internal charge pump or level-shifter is provided.

What is the purpose of the strobe input on the LM361M?

The strobe input (Pin 3) enables synchronous gating of LM361M's outputs: when strobe is low (<0.8 V), both OUTA and OUTB are forced low regardless of input state; when high (>2.0 V), normal comparator operation resumes. This allows precise timing control-e.g., aligning decisions to system clocks or blanking during transient events. Strobe draws −1.6 mA when low, permitting direct drive from microcontroller GPIO pins without buffering. LM361M's strobe delay is 8 ns, ensuring minimal added latency.

Is the LM361M pin-compatible with the SE529/NE529 comparator?

Yes, the LM361M is explicitly specified as a pin-for-pin replacement for the SE529 and NE529 comparators, sharing identical pinout, supply connections, and output behavior. Key improvements include lower input offset voltage (1–5 mV vs up to 10 mV), tighter delay matching (≤5 ns skew vs unspecified), and guaranteed 20 ns max propagation delay. No PCB changes are required when upgrading from SE529/NE529 to LM361M, and all existing schematics and layouts remain valid.