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5V 1.5A Voltage Regulator Through Hole

5V 1.5A Voltage Regulator Through Hole

Regular price $1.50 USD
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The 7805 is a popular member of the 78xx linear voltage regulator family. It provides a fixed +5V DC output voltage and is widely used in electronic circuits for stable power supply applications.

Key Specifications:

  • Input Voltage Range: 7V to 35V DC
  • Output Voltage: +5V DC (±4% tolerance)
  • Maximum Output Current: 1A
  • Dropout Voltage: Typically 2V
  • Line Regulation: Typically 0.01% per volt
  • Load Regulation: Typically 15mV maximum
  • Output Noise Voltage: 40μV/V
  • Operating Temperature Range: 0°C to +125°C
  • Short Circuit Protection: Built-in
  • Thermal Overload Protection: Built-in

Physical Characteristics:

  • Available in multiple packages:
    • TO-220 (most common)
    • TO-252 (surface mount)
    • TO-263 (surface mount)
  • For TO-220 package:
    • Pin 1: Input
    • Pin 2: Ground
    • Pin 3: Output

Thermal Considerations:

  • Maximum Junction Temperature: 125°C
  • Thermal Resistance (Junction to Case): 5°C/W
  • Power Dissipation: Depends on package and heat sinking
  • Heat sink often required for currents above 500mA

Application Notes:

  1. Input and output capacitors recommended:
    • 0.33μF input capacitor
    • 0.1μF output capacitor
  2. Minimum 2V headroom required between input and output
  3. Power dissipation (W) = (Vin - Vout) × Output Current

Detailed Operating Principles:

  1. Linear Regulation Method
  • Uses a series-pass transistor operating in its linear region
  • Internal error amplifier continuously monitors output voltage
  • Feedback system adjusts series transistor conductivity to maintain 5V output
  • Internal voltage reference (typically bandgap) provides stable reference point
  • Operates as a closed-loop negative feedback system

Internal Protection Features:

  1. Thermal Shutdown
  • Activates at junction temperatures around 150°C
  • Gradually reduces output current as temperature rises
  • Automatically recovers when temperature drops
  • Hysteresis prevents oscillation during thermal events
  1. Short Circuit Protection
  • Current limiting typically triggers at 1.2A to 1.5A
  • Foldback current limiting reduces power dissipation during shorts
  • Safe operating area protection for internal transistors
  • Auto-recovery when short is removed
  1. Safe Operating Area (SOA) Protection
  • Prevents simultaneous high-voltage and high-current operation
  • Protects internal pass transistor from secondary breakdown
  • Monitors and limits power dissipation dynamically

Expanded Electrical Characteristics:

  1. DC Parameters
  • Quiescent current: typically 4-8mA
  • Minimum load current: 5mA for proper regulation
  • Peak current capability: 2.2A (absolute maximum)
  • Temperature coefficient: typically 0.6mV/°C
  • Long-term stability: approximately 25mV/1000hr
  1. AC Parameters
  • Ripple rejection: 80dB typical at 120Hz
  • Turn-on delay: approximately 50μs
  • Output impedance: 0.018Ω typical
  • Bandwidth: approximately 1MHz

Thermal Management Details:

  1. Heat Dissipation
  • Power dissipation = (Vin - 5V) × Iout
  • Maximum junction temperature = Ambient temp + (Power × θJA)
  • θJA varies by package and heatsink:
    • TO-220 without heatsink: ~65°C/W
    • TO-220 with basic heatsink: ~15-30°C/W
    • TO-220 with large heatsink and fan: ~5°C/W
  1. Heatsink Selection Guide:
  • Required thermal resistance = (TJmax - Tambient) / Power - θJC
  • Recommended safety margin: 20% additional cooling capacity
  • Surface preparation important: thermal compound recommended
  • Mounting torque typically 0.4-0.6 N·m

Application Design Considerations:

  1. Input Protection
  • Reverse polarity protection diode recommended
  • Input surge protection using TVS diode advised
  • LC filter for noisy input sources
  • Bulk capacitor sizing: minimum 10μF per amp of load
  1. Output Stability
  • Minimum output capacitor: 0.1μF ceramic
  • Recommended output capacitor: 1-10μF for better transient response
  • Low ESR capacitors improve ripple rejection
  • Keep capacitor leads short to prevent oscillation
  1. PCB Layout Guidelines
  • Wide traces for power paths (minimum 0.050" for 1A)
  • Separate ground paths for power and signal
  • Input/output capacitors close to device pins
  • Kelvin ground connection for better regulation
  • Thermal relief pads for easier soldering

Common Applications:

  1. Fixed Power Supplies
  • Converting 9V/12V to 5V for digital circuits
  • USB power supply (with current limiting)
  • Microcontroller power supplies
  • Sensor power supplies
  1. Special Applications
  • Post-regulation for switching supplies
  • Battery-powered equipment
  • Vehicle accessories (with proper input protection)
  • Laboratory power supplies

Troubleshooting Guide:

  1. Common Issues
  • Output voltage low: check input voltage headroom
  • Excessive heating: verify power dissipation calculations
  • Oscillation: check capacitor placement and values
  • Poor regulation: verify ground connections
  • Noise on output: improve filtering and layout
  1. Performance Optimization
  • Use ground plane for better heat distribution
  • Add input filter for noisy environments
  • Consider pre-regulator for high voltage differences
  • Use parallel regulators for higher current

 

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