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LM339 vs LM339N:Voltage Comparator IC

Update time : 2025-09-12 14:59:46

Voltage comparators are critical components in analog circuits, designed to compare two input voltages and output a digital signal (high or low) based on which input is larger. Among the most widely used comparators are the LM339 and LM339N, both belonging to Texas Instruments’ (TI) family of quad voltage comparators. While they share core functionality, subtle differences in packaging, specifications, and application suitability make each unique. This article explores their similarities, differences, and practical use cases to help engineers make informed design choices.

What Are LM339 and LM339N?

The LM339 and LM339N are quad voltage comparators, meaning each IC integrates four independent comparators in a single package. They are designed for general-purpose applications, offering low power consumption, wide voltage ranges, and robust performance—traits that have made them staples in consumer electronics, industrial control systems, and automotive circuits.

LM339: A generic designation for the quad comparator IC, available in various package types.
LM339N: A specific variant of the LM339, distinguished primarily by its through-hole DIP (Dual Inline Package)—the "N" suffix indicates a plastic DIP-14 package, a common form factor for through-hole assembly.

Core Similarities

The LM339 and LM339N are functionally nearly identical, sharing key specifications and capabilities that make them interchangeable in most circuits:

1. Quad Comparator Configuration

Both ICs include four independent comparators, each with two input pins (inverting and non-inverting) and one output pin. This allows them to handle multiple comparison tasks simultaneously (e.g., monitoring four different sensor signals in a single circuit).

2. Wide Supply Voltage Range

They operate over a broad supply voltage range, from 2V to 36V for single-supply configurations, or ±1V to ±18V for dual-supply setups. This flexibility makes them suitable for low-voltage battery-powered devices (e.g., 3V sensors) and higher-voltage industrial systems (e.g., 24V control circuits).

3. Open-Collector Outputs

A defining feature of both ICs is their open-collector outputs, which do not include internal pull-up resistors. This design allows:

Flexible output voltage levels (by connecting the output to an external voltage rail via a pull-up resistor).
Wired-OR configurations (multiple outputs can be tied together to create logical OR functions without damaging the ICs).

4. Low Power Consumption

Typical quiescent current is around 2mA (total for all four comparators), making them ideal for low-power applications such as battery-operated devices (e.g., smoke detectors, portable meters).

5. Common-Mode Voltage Range

Their common-mode input range extends from 0V to the positive supply voltage minus 1.5V (in single-supply mode), enabling them to compare signals close to ground—critical for circuits like level shifters or zero-crossing detectors.

6. Temperature Range

Both operate reliably across a commercial temperature range of 0°C to 70°C, suitable for most consumer and industrial environments. Extended-temperature variants (e.g., LM339A) are available for harsh conditions (-40°C to 85°C), but these are distinct from the standard LM339/LM339N.

Key Differences: LM339 vs. LM339N

The primary distinction between the LM339 and LM339N lies in packaging, which influences assembly methods, PCB design, and application suitability:

Feature	LM339	LM339N
Package Type	Available in multiple packages: DIP-14 (plastic/ceramic), SOIC-14 (surface-mount), TSSOP-14, etc.	Exclusively a plastic through-hole DIP-14 package.
Assembly Method	Flexible: through-hole (DIP) or surface-mount (SOIC, TSSOP).	Strictly through-hole (requires soldering to DIP sockets or PCB holes).
Footprint Size	Varies by package; surface-mount versions (e.g., SOIC-14) have smaller footprints (~6mm × 10mm).	Larger footprint (DIP-14: ~19mm × 6.5mm) due to through-hole pins.
Heat Dissipation	Surface-mount packages (e.g., SOIC) offer better thermal conductivity to PCBs.	DIP-14 relies on pin conduction for heat dissipation; less efficient than surface-mount in high-power scenarios.
Cost	Slightly higher for specialized packages (e.g., ceramic DIP).	Generally lower due to standardized plastic DIP-14 production.

Performance Specifications: Are They Identical?

Yes—when comparing the LM339 (in DIP-14 packaging) and LM339N, their electrical specifications are identical. Key parameters include:

Input Offset Voltage: Max 5mV (typical 2mV), ensuring accurate comparison of small voltage differences.
Input Bias Current: Max 250nA, minimizing loading on input signals (critical for high-impedance sources like sensors).
Response Time: Typically 300ns, allowing rapid switching between high/low outputs for fast-changing signals.
Output Sink Current: Up to 16mA, sufficient to drive LEDs, relays, or logic gates (with appropriate pull-up resistors).

These specifications make both ICs suitable for applications like:

Voltage Level Detection: Monitoring battery voltage to trigger low-battery warnings.
Window Comparators: Detecting if a signal falls within a specific voltage range (e.g., over-voltage/under-voltage protection).
Zero-Crossing Detectors: Synchronizing circuits with AC line voltage (e.g., in light dimmers or motor controllers).
Signal Conditioning: Converting analog sensor outputs (e.g., from thermistors or photodiodes) to digital signals for microcontrollers.

Practical Applications: Choosing Between Them

The choice between LM339 and LM339N hinges on packaging needs rather than performance. Here’s how to decide:

Choose LM339 (Non-N Variants) When:

Surface-Mount Assembly is required: Use SOIC-14 or TSSOP-14 packages for compact PCBs (e.g., wearable devices, IoT modules).
Thermal Management is critical: Surface-mount packages dissipate heat more efficiently in high-power circuits (e.g., industrial motor controls).
Special Environments demand ruggedness: Ceramic DIP packages offer better resistance to vibration or extreme temperatures (e.g., automotive under-hood applications).

Choose LM339N When:

Through-Hole Assembly is preferred: Ideal for prototyping, hobby projects, or legacy systems using DIP sockets (easier to replace).
Cost Sensitivity is high: The standardized plastic DIP-14 package is often the most affordable option.
Manual Soldering is required: DIP-14 pins are easier to hand-solder than tiny surface-mount leads.

Common Misconceptions

Myth: "LM339N is a newer or improved version of LM339."
Fact: The "N" denotes packaging (plastic DIP-14), not a performance upgrade. The LM339 family includes the LM339N as a subset.
Myth: "LM339N cannot handle high voltages."
Fact: Like all LM339 variants, the LM339N supports up to 36V, making it suitable for industrial 24V systems.
Myth: "Surface-mount LM339s are more reliable than LM339N."
Fact: Reliability depends on application conditions. Surface-mount is better for vibration-prone environments (e.g., automotive), while DIP-14 (LM339N) excels in prototyping or low-vibration settings.

Conclusion

The LM339 and LM339N are functionally identical quad voltage comparators, differing only in packaging. The LM339 offers flexibility with multiple package options (surface-mount and through-hole), while the LM339N is a cost-effective, through-hole DIP-14 variant.

When selecting between them:

Prioritize LM339 (surface-mount) for compact, high-performance designs or thermal-critical applications.
Choose LM339N for prototyping, through-hole assembly, or cost-sensitive projects.

Both ICs deliver reliable, low-cost performance, solidifying their role as go-to components for voltage comparison in countless electronic systems.

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