In-depth Analysis of LM393P Layout and Soldering Process

 

^{October 15, —2025 With the continuous growth in demand for cost-sensitive applications in industrial control and consumer electronics, high-performance yet economical voltage comparators are becoming core components in fundamental circuit design. The widely adopted industry-standard LM393P dual differential comparator, with its wide voltage range (2V to 36V) and open-collector output characteristics, provides an economical and reliable voltage comparison solution for motor control, level detection, and sensor interface circuits.}

 

^{I. Chip Introduction}

 

 

^{The LM393P is a monolithic integrated circuit that integrates two independent voltage comparators. This device features a standard DIP-8 package, offering low power consumption, high precision, and a wide power supply voltage range, and is directly compatible with TTL, CMOS, and MOS logic interfaces.}

 

^{Core Features and Advantages:}

^{Wide operating voltage range: Single supply 2V to 36V, dual supply ±1V to ±18V}

^{Low input bias current: Typically 25nA}

^{Low input offset voltage: Typically ±2mV}

^{Open-collector output: Supports flexible output level configuration}

^{Low-power design: Quiescent current only 0.4mA per comparator (at Vcc=5V)}

 

 

^{II. Pin Configuration and Functional Analysis}

 

 

^{Package Type Overview}

^{Standard 8-pin packages: Includes multiple package formats such as DIP-8, SOIC-8, and TSSOP-8}

^{Thermally enhanced packages: Selected models feature exposed thermal pads at the bottom for improved heat dissipation performance}

 

^{Pin Function Definitions:}

 

^{1. Channel 1 Related Pins}

^{Pin 1 (1OUT): Comparator A Output}

^{Open-collector output structure}

^{Requires external pull-up resistor}

^{Pin 2 (1IN-): Comparator A Inverting Input
Pin 3 (1IN+): Comparator A Non-inverting Input}

 

^{2. Channel 2 Related Pins}

^{Pin 7 (2OUT): Comparator B Output
Also features open-collector output structure}

^{Pin 6 (2IN-): Comparator B Inverting Input}

^{Pin 5 (2IN+): Comparator B Non-inverting Input}

 

 

^{Thermal Pad Design Essentials:}

^{Must be directly connected to the GND pin (Pin 4)}

^{Provides an optimal heat dissipation path}

^{PCB design should include ample copper pouring and thermal vias}

 

^{Key Design Considerations}

 

^{1. Output Configuration Requirements}

^{All outputs feature open-collector structure}

^{External pull-up resistors to positive supply are mandatory}

^{Select pull-up resistor values based on load and speed requirements (typical range: 1kΩ to 10kΩ)}

 

^{2. Power Supply Decoupling Design}

^{Place 0.1μF ceramic capacitor close to Vcc pin}

^{For high-frequency applications, additional parallel 10μF electrolytic capacitor is recommended}

 

^{3. Input Protection Measures}

^{Input voltage should not exceed power supply voltage range}

^{For sensitive applications, series current-limiting resistors can be added at inputs}

 

^{This pin configuration analysis provides comprehensive technical guidance for the circuit design and PCB layout of the LM393P, ensuring stable and reliable performance across various application scenarios.}

 

 

^{III. Analysis of Single Comparator Functional Block Diagram}

 

^{Core Architecture Overview
The LM393P employs a classic bipolar transistor differential input architecture, where each comparator comprises a complete input stage, gain stage, and output stage circuit, ensuring stable comparison functionality across a wide voltage range.}

 

 

^{Analysis of Main Functional Modules}

 

^{1. Input Differential Amplifier Stage}

^{Core Structure: Q1 and Q2 form a PNP differential input pair}

^{Bias Circuit: Q15 constitutes a tail current source (Itail), providing stable operating current}

^{Protection Design:}

^{D3 and D4 implement input clamp protection}

^{VCM Clamp provides common-mode voltage limitation}

 

^{Technical Characteristics:}

^{High input impedance supporting weak signal detection}

^{Wide common-mode input range (including ground potential)}

^{Low input bias current (typically 25nA)}

 

^{2. Bias and Reference Network}

^{Bias Generation: Q9-Q12 and Q14 form a precision current mirror}

^{Level Shifting: D1 and D2 provide stable voltage biasing}

^{Temperature Compensation: Built-in compensation ensures full-temperature-range stability}

 

^{3. Intermediate Gain Stage}

^{Amplification Structure: Q3, Q4, etc. form a common-emitter amplifier circuit}

^{Functional Roles:}

^{Provides primary voltage gain}

^{Implements differential-to-single-ended signal conversion}

^{Drives the output stage operation}

 

^{4. Output Driver Stage}

^{Output Structure: Q13 serves as open-collector output transistor}

^{ESD Protection: Integrated electrostatic discharge protection circuit}

^{Key Features:}

^{Compatible with TTL/CMOS logic levels}

^{Low output saturation voltage (typically 130mV)}

^{Requires external pull-up resistor}

 

Signal Path Analysis

Positive Input → Q2 → Level Shifting → Gain Stage → Output Driver Negative Input → Q1 → Level Shifting → Gain Stage → Output Driver

 

 

^{Key Performance Characteristics}

 

^{Precision Specifications}

^{Input offset voltage: Maximum ±2mV}

^{Input bias current: Typically 25nA}

^{Voltage gain: Typically 200V/mV}

 

^{Speed Performance}

^{Response time: Typically 1.3μs}

^{Propagation delay: Meets requirements for most applications}

 

^{Reliability Design}

^{ESD Protection: Enhanced anti-static capability}

^{Input Protection: Prevents overvoltage damage}

^{Thermal Stability: Consistent performance across full temperature range}

 

 

^{Design Advantages Summary}

^{This architecture embodies the design philosophy of classic analog integrated circuits, achieving the following while ensuring performance:}

^{High Reliability: Comprehensive built-in protection mechanisms}

^{Wide Voltage Operation: Supports 2V to 36V supply range}

^{Low Power Consumption: Quiescent current of only ~0.4mA per comparator}

^{Temperature Stability: Maintains performance across industrial temperature ranges}

 

^{This functional block diagram analysis provides crucial technical reference for in-depth understanding and application design of the LM393P, particularly suitable for industrial control and consumer electronics applications requiring high-precision voltage comparison.}

 

 

IV. Analysis of Typical Application Circuits

 

 

Single-Ended Comparator Configuration

 

 

 

Differential Comparator Configuration

 

^{Comparison Logic:}

^{When Vin+ > Vin-: Output low level}

^{When Vin+ < Vin-: Output high-impedance state}

 

^{Application Scenarios:}

^{Signal difference detection}

^{Window comparator}

^{Zero-crossing detection circuit}

 

^{Core Design Parameters}

 

^{1. Power Supply Configuration}

^{Operating Voltage Range: 2V to 36V (Single Supply)}

^{Dual Supply Mode: ±1V to ±18V}

^{Quiescent Current: Approximately 0.4mA per comparator (Vcc=5V)}

 

^{2. Output Characteristics}

^{Open-collector output: Requires pull-up resistor}

^{Output saturation voltage: Typically 130mV (at Isink=4mA)}

^{Logic compatibility: Supports TTL/CMOS levels}

 

^{3. Performance Parameters}

^{Response time: Typically 1.3μs}

^{Input bias current: Maximum 50nA}

^{Input offset voltage: Maximum ±2mV}

 

 

^{4.Typical Application Scenarios}

^{Voltage Monitoring}

^{Battery level detection}

^{Power supply voltage monitoring}

^{Overvoltage/undervoltage protection}

 

^{Signal Conditioning}

^{Square wave generator}

^{Pulse width detection}

^{Analog-to-digital conversion interface}

 

^{Control Applications}

^{Temperature control switch}

^{Motor control circuit}

^{Photoelectric sensor interface}

 

 

5.Design Considerations

 

Pull-up Resistor Selection

Calculation formula: Rpullup = (Vlogic - Vol) / Iol_sink Recommended range: 1kΩ to 10kΩ Trade-off factors: Power consumption vs switching speed
 

^{Noise Suppression Measures}

^{Add RC filtering at inputs}

^{Implement local decoupling at power pins}

^{Apply shielding protection for sensitive signal lines}

 

^{Layout Considerations}

^{Route input signals away from output traces}

^{Maintain continuous ground plane to reduce noise}

^{Thermal pads (if present) must be grounded}

 

^{These application circuits demonstrate the flexibility and reliability of the LM393P as a classic voltage comparator. With simple configuration, it can meet various voltage detection and signal processing requirements, making it particularly suitable for cost-sensitive industrial control and consumer electronics applications.}

 

 

V. PCB Layout Design Guide

 

 

^{Layout Core Principles}

^{Input Signal Processing}

^{Input resistors placed close to device: Reduces noise coupling and signal reflection}

^{Sensitive signal isolation: Input traces routed away from output and power lines}

^{Symmetrical layout: Differential input signals use equal-length traces}

 

 

^{Power Supply Decoupling Design}

^{Vcc pin → 0.1μF ceramic capacitor → GND}

^{Decoupling capacitors placed adjacent to power pins}

^{Use short and wide connection traces}

^{Add 10μF electrolytic capacitor for high-frequency applications}

 

^{Layout Optimization Strategies}
 

^{1. Component Zoning Layout}

[Input Zone] → [LM393P Chip] → [Output Zone]
↓ ↓ ↓
Input Resistors Core Comparator Pull-up Resistors
Signal Filtering Decoupling Caps Load Drive

 

^{2. Grounding Techniques}

^{Single-point Grounding: Separate analog ground from digital ground}

^{Ground Plane: Provides stable reference ground potential}

^{Thermal Pad Connection: Directly connected to GND pin}

 

^{Key Layout Details}

^{Input Section Layout}

^{Input resistors placed <5mm from chip pins}

^{Avoid parallel routing of input and output signal lines}

^{Shield sensitive input signals with ground traces}

 

^{Power Supply Section Layout}

^{Power trace width ≥0.5mm (for 1A current)}

^{Place decoupling capacitors on the same layer as the chip}

^{Power filtering sequence: large capacitors before small capacitors}

 

^{Output Section Layout}

^{Place pull-up resistors close to output pins}

^{Determine output trace width based on load current}

^{Prevent output signals from causing crosstalk to inputs}

 

^{Anti-Interference Measures}

 

^{1. Noise Suppression}

^{Parallel small capacitors at input pins for filtering (optional)}

^{Surround critical signals with ground planes}

^{Avoid routing under crystals or switching power supplies}

 

^{2. Thermal Management}

^{Fully utilize thermal pad for heat dissipation}

^{Add thermal vias for high-power applications}

^{Maintain airflow around components}

 

^{Manufacturing Design Considerations}

^{Manufacturability}

^{Component spacing meets soldering requirements}

^{Test points accessible for in-circuit testing}

^{Clear silkscreen labeling for critical signals}

 

^{Reliability Assurance}

^{Pad dimensions comply with IPC standards}

^{Avoid acute angle traces}

^{Ensure sufficient trace spacing}

 

^{This layout solution ensures optimal performance of the LM393P across various application scenarios by optimizing signal integrity, power integrity, and thermal management, making it particularly suitable for noise-sensitive high-precision measurement circuits.}

 

 

VI. PCB Pad Layout and Solder Mask Design Guide

 

 

 

^{Key Pad Layout Specifications}

^{Basic Dimension Parameters}

^{Number of pins: 8-pin standard layout}

^{Pin pitch: 1.27mm (0.050 inch)}

^{Pin width: 0.6mm (0.024 inch)}

^{Pad length: 1.55mm (0.061 inch)}

 

^{Symmetry Requirements}

^{Fully symmetrical layout based on centerline}

^{All dimensional tolerances: ±0.05mm (0.002 inch)}

^{Overall span: 5.4mm (0.213 inch)}

 

^{Solder Mask Design Specifications}

^{Non-Solder Mask Defined (NSMD) - Recommended Solution
Pad structure: Metal pad fully exposed Aperture size: Solder mask opening 0.07mm larger than pad (per side) Advantages: Reduces stress concentration, improves soldering reliability}

 

^{Solder Mask Key Parameters}

^{Aperture tolerance: Maximum 0.07mm (all directions)}

^{Metal coverage: Metal extends ≥0.07mm under solder mask}

^{Alignment accuracy: Ensures complete pad exposure}

 

^{Metallization Requirements}

^{Pad Metal Structure}

^{Base material: PCB copper foil (recommended 1oz thickness)}

^{Surface finish: ENIG/Immersion Gold/Immersion Silver (selected per application)}

^{Pad shape: Rectangular with 0.05mm corner radius}

 

^{Aperture Size Optimization}

^{Width: 90-100% of pin width}

^{Length: Equal to or slightly shorter than pad length}

^{Stencil thickness: 0.1-0.15mm (4-6mil)}

 

^{Process Parameters}

^{Solder paste type: Type III fine grain lead-free solder paste}

^{Printing accuracy: ±0.05mm alignment tolerance}

^{Reflow profile: Standard SMT reflow process}

 

^{Design Verification Points}

^{Manufacturability Check}

^{Pad spacing meets minimum electrical clearance requirements}

^{Solder mask bridge width ≥0.1mm to ensure insulation reliability}

^{Clear silkscreen markings without pad coverage}

 

^{Reliability Verification}

^{Thermal cycle testing: Certified to JEDEC standards}

^{Mechanical strength: Pin pull-off force complies with IPC standards}

^{Solder quality: Solder joints meet IPC-A-610 Class 2/3 requirements}

 

^{Application Considerations}

^{High-Density Routing}

^{NSMD design recommended for fine trace routing}

^{Allows one 0.15mm signal trace between pins}

^{Maintain minimum 0.2mm trace spacing}

 

^{Thermal Enhancement}

^{Add 0.3mm diameter thermal vias in thermal pad area}

^{Expand heat dissipation area with backside copper pour}

^{Consider CTE matching for high-temperature applications}

 

^{This design guide provides complete pad layout and solder mask technical specifications for the LM393P, ensuring high yield rates in mass production and long-term reliability, making it particularly suitable for automated SMT production processes.}

 

 

^{VII. PCB Layout and Stencil Aperture Design Guide}

 

 

^{Pad Layout Specifications}

^{Basic Dimension Parameters}

^{Pin pitch: 6×1.27mm standard spacing}

^{Pad width: 0.55mm (meets pin contact requirements)}

^{Pad length: 1.80mm (provides sufficient soldering area)}

^{Overall span: 7.40mm (total package width)}

 

^{Geometric Feature Requirements}

^{Maintain 0.60mm clearance between pad edges}

^{Implement rounded corners to avoid stress concentration at sharp angles}

^{Ensure symmetrical layout for uniform soldering}

 

Stencil Aperture Dimension Specifications

 

Stencil aperture length: 1.75mm Stencil aperture width: 0.55mm Aperture-to-pad ratio: 1:1 correspondence

^{Process Parameter Configuration}

^{Stencil Thickness: Recommended 0.10-0.15mm}

^{Aperture Tolerance: ±0.05mm}

^{Solder Paste Release: Ensure >90% transfer efficiency}

 

^{Solder Mask Design Key Points}

 

^{Non-Solder Mask Defined (NSMD)}

^{Solder mask opening 0.07mm larger than pad (uniform on all sides)}

^{Metal pads fully exposed without solder mask coverage}

^{Reduces stress concentration and improves soldering reliability}

 

^{Alignment Accuracy Requirements}

^{Solder mask to pad center offset ≤0.05mm}

^{Solder mask bridge width ≥0.15mm, ensuring insulation reliability}

 

^{Manufacturing Process Control}

 

^{Printing Process Parameters}

^{Solder paste type: Type III fine grain lead-free}

^{Squeegee pressure: 4-6kgf, 45-60° angle}

^{Printing speed: 20-40mm/s uniform motion}

 

^{Quality Control Standards}

 

^{Acceptance Criteria}

^{Solder joint fill rate ≥75%}

^{No bridging or cold solder defects}

^{Pin-to-pad alignment tolerance ±0.1mm}

 

^{Inspection Methods}

^{2D/3D Solder Paste Inspection (SPI)}

^{X-ray solder joint quality analysis}

^{Automated Optical Inspection (AOI)}

 

^{This design guide provides complete process parameters and quality control standards for mass production of the LM393P, ensuring stable soldering quality and excellent long-term reliability in high-speed}

^{SMT manufacturing.}

 

 

VIII. PCB Pad Layout and Solder Mask Design Analysis

 

Core Parameters of Pad Layout

 

 

 

 

^{Basic Dimension Specifications}

^{Number of Pins: 8-pin standard configuration}

^{Pad Width: 0.45mm (meets standard pin contact requirements)}

^{Pad Length: 1.5mm (provides sufficient soldering area)}

^{Pin Pitch: 0.65mm (standard pitch design)}

^{Package Span: 5.8mm (overall symmetrical layout)}

 

^{Symmetry Design Requirements}

^{Fully symmetrical layout based on centerline}

^{Maintain strict proportional relationships for all dimensions}

^{Ensure uniform heat distribution during soldering}

 

^{Solder Mask Design Standards
Non-Solder Mask Defined (NSMD) - Recommended Solution}

^{Structural Features:}

^{Metal pads fully exposed}

^{Solder mask openings larger than pad dimensions}

^{Metal extends beneath the solder mask layer}

 

^{Solder Mask Defined (SMD) - Alternative Solution}

^{Solder mask openings precisely match pad dimensions}

^{Suitable for high-density routing designs}

^{Requires stricter process control}

 

^{Manufacturing Process Key Points
Stencil Design Recommendations}

^{Aperture size: 1:1 ratio to pad dimensions}

^{Stencil thickness: 0.10-0.15mm standard range}

^{Aperture accuracy: ±0.02mm tolerance control}

 

^{Welding Quality Assurance}

^{Use Type III fine-grained solder paste}

^{Recommended reflow peak temperature 245-255°C}

^{Cooling rate controlled at 2-4°C/second}

 

^{Design Verification Standards}

^{Manufacturability Check}

^{Pad spacing meets minimum electrical clearance requirements}

^{Solder mask bridge width ≥0.1mm ensures insulation reliability}

^{Silkscreen markings are clear and do not cover pads}

 

^{Reliability Verification}

^{Thermal cycle testing complies with JEDEC standards}

^{Solder joint strength passes IPC pull tests}

^{Visual inspection meets IPC-A-610 Class 2/3 requirements}

 

^{This design guide provides complete pad layout and solder mask technical specifications for the LM393P, ensuring high yield rates in mass production and long-term reliability, making it particularly suitable for automated SMT production process requirements.}