MAX7456EUI Achieves Integrated Decoding and Display

 

 

 

^{October 19, 2025 — With the continuous growth in demand for video overlay functions in drone flight control systems and industrial monitoring equipment, highly integrated OSD (On-Screen Display) chips are becoming core components of video processing systems. The widely adopted industry-standard MAX7456EUI single-channel OSD generator, with its high integration and automatic NTSC/PAL detection capabilities, provides a reliable character overlay solution for drone FPV systems, industrial monitoring equipment, and automotive video systems.}

 

 

^{I. Chip Introduction: MAX7456EUI}

 

^{The MAX7456EUI is a single-channel on-screen display (OSD) generator with integrated EEPROM, packaged in a 28-pin TSSOP. This device features high integration, low power consumption, and automatic sync detection, enabling direct overlay of character graphics onto NTSC or PAL composite video signals.}

 

^{Core Features and Advantages:}

^{Highly Integrated Design: Built-in EEPROM for storing user-defined characters}

^{Automatic Format Detection: Supports automatic NTSC/PAL standard recognition}

^{Single Supply Operation: 3.0V to 3.6V operating voltage range}

^{Low Power Performance: Typical operating current of 4mA}

^{Extensive Character Set: 256 built-in user-programmable characters}

 

^{Typical Application Fields:}

^{Drone FPV video systems}

^{Industrial monitoring equipment}

^{Automotive video displays}

^{Security surveillance systems}

 

 

^{II. Simplified Functional Block Diagram Analysis}

 

^{Core Architecture Overview
The MAX7456EUI adopts a highly integrated video processing architecture, comprising four main functional modules: video processing, character generation, storage management, and control interface, enabling complete on-screen display (OSD) functionality.}

 

 

 

^{Detailed Module Function Analysis}

 

^{1. Video Processing Module}

^{Sync Separator:}

^{Extracts horizontal sync (HSYNC) and vertical sync (VSYNC) from video signals}

^{Automatically identifies NTSC/PAL standards}

^{Generates precise timing reference signals}

 

^{Clamp Circuit (CLAMP):}

^{Stabilizes video DC level}

^{Eliminates signal drift effects}

^{Maintains signal consistency}

 

 

^{2. Clock and Timing Module}

^{Crystal Oscillator (OSCILLATOR):}

^{External crystal provides reference clock}

^{Supports multiple frequency configurations}

^{Ensures system clock stability}

 

^{Timing Generator (TIMING GENERATOR):}

^{Generates display timing control signals}

^{Coordinates working rhythm of all modules}

^{Guarantees precise character overlay positioning}

 

^{3. Character Generation and Storage Module}

^{Display Memory (RAM):}

^{Stores current screen display content}

^{Capacity supports multi-page display}

^{Real-time display data updating}

 

^{Character Memory (ROM):}

^{256 built-in character templates}

^{Supports user-defined characters}

^{Provides multiple font options}

 

^{OSD Generator:}

^{Converts character codes into pixel data}

^{Implements character scaling and special effects}

^{Controls display attributes}

 

^{4. Control Interface Module}

^{SPI Serial Interface:}

^{Communicates with external microcontroller}

^{Supports configuration parameter writing}

^{Implements display data updates}

 

^{Control Logic:}

^{Parses external control commands}

^{Manages system operating status}

^{Handles reset and power management}

 

^{Signal Flow Analysis}

 

^{Video Processing Path}

^{Video Input → Clamp Circuit → Sync Separation → Timing Generation → Mixed Output ↓ Character Overlay Control ↓ OSD Generator → DAC → Video Output}

 

^{Data Processing Path}

^{SPI Interface → Control Logic → Display Memory → Character Memory ↓ OSD Generator → Pixel Output}

 

^{Control Flow Path}

^{External Control → SPI Interface → Configuration Registers → Functional Modules ↓ Status Monitoring → Output Feedback}

 

 

^{Key Features Detailed Explanation}

 

^{Intelligent Sync Processing}

^{Automatically adapts to different video standards}

^{Real-time tracking of signal timing changes}

^{Ensures character display stability}

 

^{Flexible Display Control}

^{Programmable display positions}

^{Multiple background display modes}

^{Supports transparent and semi-transparent effects}

 

^{Efficient Storage Management}

^{Layered storage architecture}

^{Fast character retrieval}

^{Supports dynamic updates}

 

^{System Integration Advantages}

 

^{Simplified Design}

^{Single chip implements complete OSD functionality}

^{Reduces number of external components}

^{Lowers system complexity}

 

^{Performance Optimization}

^{Low-power operation modes}

^{Fast response display updates}

^{High-reliability design}

 

^{This functional block diagram analysis reveals the core technical advantages of the MAX7456EUI as a high-performance OSD chip, providing comprehensive technical reference for the design and optimization of video overlay systems.}

 

 

 

^{III. Standard Test Circuit Analysis}

 

 

^{Input Test Circuit Analysis}

^{Circuit Structure}

^{Signal Generator → 75Ω Matching Resistor → 0.1μF Coupling Capacitor → VIN Pin │ │ │ 75Ω 0.1μF MAX7456 │ │ │ GND GND GND}

 

 

^{Design Points Analysis}

 

^{Impedance Matching Network}

^{75Ω standard impedance: Precisely matches video cable characteristic impedance}

^{Signal integrity: Prevents ghosting and ringing caused by signal reflection}

^{Industry standard: Complies with 75Ω industry specification for video transmission}

 

 

^{AC Coupling Design}

^{DC blocking capacitor: 0.1μF capacitor blocks DC component}

^{Signal transmission: Ensures pure AC video signal passes through}

^{Level adaptation: Eliminates DC bias differences between different devices}

 

 

^{Video Load Test Circuit Analysis}

 

^{Circuit Structure}

^{MAX7456 Output → 75Ω Load Resistor → Video Monitoring Equipment │ │ VOUT 75Ω │ │ GND GND}

 

^{Design Points Analysis}

 

^{Standard Video Load}

^{75Ω termination resistor: Simulates real video display equipment input impedance}

^{Power matching: Ensures correct signal power transmission}

^{Signal quality: Maintains proper signal level and waveform}

 

^{DC Coupling Characteristics}

^{Direct coupling: Preserves DC component of video signal}

^{Sync preservation: Ensures synchronization pulse integrity}

^{Level accuracy: Maintains precise video signal amplitude}

 

^{Test Circuit Function Details}

 

^{Performance Verification Items}

^{Input sensitivity test: Verify minimum recognizable video signal level}

^{Impedance matching verification: Ensure reflection-free signal transmission}

^{Frequency response test: Check flatness within video bandwidth}

^{Sync separation performance: Verify horizontal/vertical sync extraction accuracy}

 

^{Key Test Parameters}

^{Input signal amplitude: 1.0Vp-p standard video level}

^{Input impedance: 75Ω±5%}

^{Coupling capacitor: 0.1μF±10%}

^{Termination resistor: 75Ω±1%}

 

^{Application Design Guide}

^{PCB Layout Recommendations}

^{Place input circuits close to chip pins}

^{Maintain impedance-controlled transmission line design}

^{Minimize lead inductance of coupling capacitors}

 

^{Testing Considerations}

^{Use high-quality 75Ω coaxial cables for connections}

^{Ensure proper impedance matching settings on test equipment}

^{Pay attention to signal interference caused by ground loops}

 

^{This standard test circuit provides a reliable technical foundation for performance verification of the MAX7456EUI, ensuring optimal signal quality and display performance in video applications.}

 

 

^{IV. Analysis of Typical Operating Circuit}

 

^{Digital Power Supply Design}

^{DVDD Pin: 3.3V digital power supply input}

^{Decoupling Configuration: 0.1μF ceramic capacitor placed close to the pin}

^{Grounding Strategy: DGND digital ground connected via separate pin}

 

 

 

^{Mixed-Signal Power Architecture}

^{3.3V Main Power → 0.1μF Decoupling → DVDD (Pin 4) → 0.1μF Decoupling → Analog Circuits}

 

^{Clock Circuit Module}

^{Crystal Oscillator Configuration}

^{External crystal: Connected between CLKIN (Pin 6) and CLKOUT (Pin 8)}

^{Load capacitors: Matched to crystal's required load parameters}

^{Feedback resistor: XFB pin ensures oscillation stability}

 

^{Clock Network Features}

^{Provides system master clock reference}

^{Supports multiple crystal frequencies}

^{Guarantees character display synchronization accuracy}

 

^{Video Input Interface}

^{Composite Video Input → 0.1μF Coupling → VIN (Pin 28) → 75Ω Matching → Source Impedance}

 

^{Video Output Interface}

^{VOUT Pin: Directly drives 75Ω video load}

^{DC Coupling: Maintains video signal integrity}

^{Output Buffer: Built-in driver amplifier}

 

^{SPI Communication Interface}

^{CS (Pin 9) → Chip Select Signal SDIN (Pin 10) → Serial Data Input SCLK (Pin 11) → Serial Clock SDOUT (Pin 12) → Serial Data Output}

 

^{Control Signals}

^{LOS (Pin 13): Signal Loss Detection Output}

^{Synchronization Signals: HS (Horizontal Sync), VS (Vertical Sync)}

 

^{Signal Integrity Design}

^{Power Supply Decoupling Strategy}

^{Independent 0.1μF decoupling capacitor for each power pin}

^{High-frequency noise suppression}

^{Voltage ripple control}

 

^{Impedance Matching Design}

^{75Ω termination matching for video input}

^{Transmission line characteristic impedance control}

^{Reflection minimization}

 

^{Special Pin Handling}

^{Unconnected Pins}

^{N.C. pins remain floating}

^{Avoid external connection interference}

^{Reserved Test Points}

 

^{Synchronization Signal Processing}

^{Direct input of horizontal and vertical sync signals}

^{Automatic video standard detection}

^{Timing calibration function}

 

^{Typical Performance Parameters}

^{Operating Conditions}

^{Supply voltage: 3.3V±10%}

^{Operating temperature: -40℃ to +85℃}

^{Video standard: NTSC/PAL auto-adaptation}

 

^{Signal Characteristics}

^{Video bandwidth: >5MHz}

^{Character resolution: 12×18 pixels}

^{Display colors: Monochrome (white/black/transparent)}

 

^{Application Design Guidelines}

 

^{PCB Layout Recommendations}

^{Route video signals away from digital noise sources}

^{Place clock circuits close to chip pins}

^{Maintain clear power supply partitioning}

 

^{Thermal Management Considerations}

^{Implement TSSOP package heat dissipation design}

^{Apply derating for high-temperature environments}

^{Provide adequate copper heat dissipation area}

 

^{This typical operating circuit provides a complete application solution for the MAX7456EUI, ensuring stable and reliable character overlay functionality in various video systems, particularly suitable for space-constrained embedded video application scenarios.}

 

 

^{V. Composite Video Signal Terminology Definition Analysis}

 

 

 

Composite Video Signal Key Level Analysis

 

 

^{Core Parameter Details}

^{1. White Level}

^{Definition: The brightest luminance level in the video signal}

^{Standard Value: 100 IRE units (714mV)}

^{Function: Defines the maximum brightness output of the display}

^{MAX7456 Processing: Displays white characters in this level region}

 

^{2. Black Level}

^{Definition: The reference luminance level in the video signal}

^{Standard Values:}

^{NTSC: 7.5 IRE (54mV)}

^{PAL: 0 IRE (0mV)}

^{Function: Defines the black reference level of the display}

^{MAX7456 Processing: Displays black characters in this level region}

 

 

^{3. Sync Tip Level}

^{Definition: The lowest level of synchronization pulses}

^{Standard Value: -40 IRE (-286mV)}

^{Function: Provides timing reference for horizontal and vertical synchronization}

^{MAX7456 Processing: Used for sync separation and timing lock}

 

^{4. Color Burst Signal}

^{Position: Located on the back porch, following the sync pulse}

^{Frequency: 3.58MHz (NTSC) / 4.43MHz (PAL)}

^{Amplitude: 20 IRE (140mV)}

^{Function: Provides reference phase for color demodulation}

^{MAX7456 Processing: Detects video standard and maintains color synchronization}

 

 

^{Sync Separation Mechanism}

^{Composite Video Signal → Clamp Circuit → Sync Separation ↓ Horizontal Sync Identification ↓ Vertical Sync Identification ↓ Display Timing Generation}

 

^{OSD Overlay Principle}

• ^{White characters: Correspond to white level region}

• ^{Black characters: Correspond to black level region}

• ^{Transparent background: Maintains original video signal}

• ^{Sync preservation: Does not interfere with original sync signals}

^{Signal Amplitude Requirements}

^{Input amplitude: 1.0Vp-p standard video signal}

^{Sync amplitude: -286mV to +714mV}

^{Character overlay amplitude: Complies with white/black level standards}

 

^{Timing Characteristics}

^{Line period:}

^{NTSC: 63.5μs}

^{PAL: 64μs}

^{Field period:}

^{NTSC: 16.7ms (60Hz)}

^{PAL: 20ms (50Hz)}

 

^{Signal Integrity Assurance}

^{Maintain correct signal amplitude ratios}

^{Ensure synchronization pulse integrity}

^{Preserve color burst signal accuracy}

 

^{OSD Display Optimization}

^{Match character brightness with background contrast}

^{Avoid interference with original video content}

^{Ensure compatibility across different video standards}

 

^{This video signal terminology definition provides crucial technical benchmarks for the MAX7456EUI's application design, guaranteeing accurate and reliable character overlay display performance in various video systems.}

 

 

 

^{VI. External Synchronization Mode Timing Analysis}

 

Basic Timing Structure

Field Sync (VSYNC) → Line Sync (HSYNC) → Active Video Output (VOUT) ↓ Odd/Even Field Identification ↓ Display Cycle Control

 

 

 

^{Key Timing Parameter Details}

 

^{Vertical Sync Timing (VSYNC)}

^{Period: 16.67ms (corresponding to 60Hz field frequency)}

^{Pulse width: Typically 3H (3 line periods)}

^{Odd/Even field identification:}

^{Odd field: Starts at VSYNC falling edge}

^{Even field: Starts at VSYNC rising edge}

 

^{Horizontal Sync Timing (HSYNC)}

^{Period: 63.56μs (NTSC standard)}

^{Pulse width: 4.7μs typical value}

^{Front porch position: From sync pulse end to active video start}

 

^{Vertical Sync Period}

^{VSYNC Active Period → Multiple HSYNC Pulses → Vertical Blanking Interval ↓ Field Sync Lock ↓ Odd/Even Field Identification}

 

^{Horizontal Sync Period}

^{HSYNC Falling Edge → Line Sync Start → Color Burst Pulse → Active Video Data ↓ Line Cycle Timing ↓ OSD Position Control}

 

^{NTSC Specific Parameters}

^{Field Structure Characteristics}

^{Total lines: 525 lines/frame}

^{Active lines: 480 lines/frame}

^{Vertical blanking: 45 lines (including VSYNC period)}

 

^{External Synchronization Mode Features}

 

^{Synchronization Signal Requirements}

^{VSYNC input: Must comply with NTSC field timing}

^{HSYNC input: Must comply with NTSC line timing}

^{Phase relationship: Strictly maintain specified timing relationships}

 

^{Locking Mechanism}

^{External VSYNC → Field Timing Lock → Odd/Even Field Identification
External HSYNC → Line Timing Lock → Pixel Position Calibration}

 

^{OSD Overlay Timing Control}

^{Character Position Determination}

^{Vertical position: Based on line count after VSYNC}

^{Horizontal position: Based on pixel count after HSYNC}

^{Display window: Overlay during active video period}

 

^{Synchronization Retention Characteristics}

^{Does not alter input synchronization timing}

^{Maintains output synchronization consistent with input}

^{Ensures video signal integrity}

 

^{Design Verification Points}

^{Timing Measurement Key Points}

^{VSYNC to First HSYNC delay}

^{HSYNC to Active Video start}

^{Timing accuracy of odd/even field switching points}

 

Signal Quality Requirements

^{Sync pulse amplitude: -286mV ±10%}

^{Rise/Fall time: <100ns}

^{Timing jitter: <50ns}

 

^{This timing analysis provides accurate technical basis for the system design of MAX7456EUI in NTSC external synchronization mode, ensuring stable OSD character display and correct video signal processing.}

 

 

 

 

^{VII. 16-Bit Operation Mode Serial Communication Timing Analysis}

 

^{Communication Protocol Overview
The MAX7456EUI utilizes a standard SPI interface for 16-bit data read/write operations, supporting simultaneous access to character addresses and attribute bytes.}

 

 

 

^{Timing Signal Details}

^{Chip Select (CS)}

^{Active level: Low level enables communication}

^{Setup time: Remains stable before SCLK operation}

^{Hold time: Released after data transmission completion}

 

^{Clock Signal (SCLK)}

^{Operating mode: Data sampled on rising edge}

^{Clock frequency: Maximum 10MHz}

^{Duty cycle: 40%-60% ensures reliable sampling}

 

^{Data Input (SDIN)}

^{Transmission format: 16-bit data with MSB first}

^{Data composition:}

^{Upper 8 bits: Character address (CA7-CA0)}

^{Lower 8 bits: Character attribute control bits}

 

^{16-Bit Data Frame Structure}

^{Character Address Field (CA7-CA0)}

CA7 │ CA6 │ CA5 │ CA4 │ CA3 │ CA2 │ CA1 │ CA0
 

^{Address range: 00h-FFh (256 characters)}

^{Function: Selects specific character in character memory}

 

 

^{Character Attribute Field}

^{LB7 │ LB6 │ LB5 │ LB4 │ LBC │ LK │ BLN │ Reserved}

 

^{Key Control Bits:}

^{LBC: Local Background Control}

^{LK: Character Blink Enable}

^{BLN: Character Blanking Control}

 

 

^{Read Operation Flow}

 

^{Phase 1: Command Transmission}

^{CS falling edge → 16-bit command word → SCLK synchronization → Data transfer}

 

^{Phase 2: Data Reading}

^{Command transmission completed → SDOUT enabled → 16-bit data output → CS released}

 

^{Key Timing Parameters}

^{Setup Time Requirements}

^{CS to first SCLK rising edge: ≥50ns}

^{SDIN to SCLK rising edge: ≥30ns}

 

^{Hold Time Requirements}

^{SDIN hold after SCLK falling edge: ≥30ns}

^{Last SCLK to CS rising edge: ≥50ns}

 

^{Operating Mode Characteristics}

^{16-Bit Operation Advantages}

^{Single transfer completes address and attribute read/write}

^{Reduces communication overhead, improves efficiency}

^{Simplifies microcontroller programming logic}

 

^{Data Output Characteristics}

^{SDOUT remains in high-impedance state during non-transmission periods}

^{Output data aligned with SCLK falling edge}

^{Supports continuous read operations}

 

^{Application Design Guidelines}

^{Microcontroller Interface Recommendations}

^{Configure SPI in master mode with CPOL=0, CPHA=0}

^{Ensure 16-bit data frame length setting}

^{Implement precise timing control for chip select signals}

 

^{Error Prevention Measures}

^{Avoid changing CS state during transmission}

^{Ensure SCLK frequency remains within rated range}

^{Address communication lockout during power-up sequences}

 

^{This timing analysis provides comprehensive technical reference for MAX7456EUI's SPI interface programming, ensuring reliable character data read/write operations in embedded systems.}