SLVS074I January   1983  – July 2022 TL494


  1. Features
  2. Applications
  3. Description
  4. Simplified Block Diagram
  5. Revision History
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics, Reference Section
    6. 7.6  Electrical Characteristics, Oscillator Section
    7. 7.7  Electrical Characteristics, Error-Amplifier Section
    8. 7.8  Electrical Characteristics, Output Section
    9. 7.9  Electrical Characteristics, Dead-Time Control Section
    10. 7.10 Electrical Characteristics, PWM Comparator Section
    11. 7.11 Electrical Characteristics, Total Device
    12. 7.12 Switching Characteristics
    13. 7.13 Typical Characteristics
  8. Parameter Measurement Information
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 5-V Reference Regulator
      2. 9.3.2 Oscillator
      3. 9.3.3 Dead-time Control
      4. 9.3.4 Comparator
      5. 9.3.5 Pulse-Width Modulation (PWM)
      6. 9.3.6 Error Amplifiers
      7. 9.3.7 Output-Control Input
      8. 9.3.8 Output Transistors
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. Input Power Source
        2. Control Circuits
          1. Oscillator
          2. Error Amplifier
          3. Current-Limiting Amplifier
          4. Soft Start and Dead Time
        3. Inductor Calculations
        4. Output Capacitance Calculations
        5. Transistor Power-Switch Calculations
      3. 10.2.3 Application Curves for Output Characteristics
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Feedback Traces
      2. 12.1.2 Input/Output Capacitors
      3. 12.1.3 Compensation Components
      4. 12.1.4 Traces and Ground Planes
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Trademarks
    2. 13.2 Electrostatic Discharge Caution
    3. 13.3 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Traces and Ground Planes

  • Make all of the power (high current) traces as short, direct, and thick as possible. It is good practice on a standard PCB board to make the traces an absolute minimum of 15 mils (0.381 mm) per Ampere.
  • The inductor, output capacitors, and output diode should be as close to each other possible. This helps reduce the EMI radiated by the power traces due to the high switching currents through them. This will also reduce lead inductance and resistance as well, which in turn reduces noise spikes, ringing, and resistive losses that produce voltage errors.
  • The grounds of the IC, input capacitors, output capacitors, and output diode (if applicable) should be connected close together directly to a ground plane. It would also be a good idea to have a ground plane on both sides of the PCB. This will reduce noise as well by reducing ground loop errors as well as by absorbing more of the EMI radiated by the inductor.
  • For multi-layer boards with more than two layers, a ground plane can be used to separate the power plane (where the power traces and components are) and the signal plane (where the feedback and compensation and components are) for improved performance.
  • On multi-layer boards the use of vias will be required to connect traces and different planes.
  • It is good practice to use one standard via per 200 mA of current if the trace will need to conduct a significant amount of current from one plane to the other.
  • Arrange the components so that the switching current loops curl in the same direction. Due to the way switching regulators operate, there are two power states. One state when the switch is on and one when the switch is off. During each state there will be a current loop made by the power components that are currently conducting. Place the power components so that during each of the two states the current loop is conducting in the same direction. This prevents magnetic field reversal caused by the traces between the two half-cycles and reduces radiated EMI.