SLVS915C February   2010  – July 2015 TPS73801

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Adjustable Operation
      2. 7.3.2 Fixed Operation
      3. 7.3.3 Overload Recovery
      4. 7.3.4 Output Voltage Noise
      5. 7.3.5 Protection Features
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Output Capacitance and Transient Response
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
      1. 10.3.1 Calculating Junction Temperature
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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10 Layout

10.1 Layout Guidelines

  1. For best performance, all traces should be as short as possible.
  2. Use wide traces for IN, OUT, and GND to minimize the parasitic electrical effects.
  3. A minimum output capacitor of 10 μF with an ESR of 3 Ω or less is recommended to prevent oscillations. X5R and X7R dielectrics are preferred.
  4. Place the Output Capacitor as close as possible to the OUT pin of the device.
  5. The tab of the DCQ package should be connected to ground.

10.2 Layout Example

TPS73801 layex1_slvs915.gifFigure 28. SOT-223 Layout Example (DCQ)

10.3 Thermal Considerations

The power handling capability of the device is limited by the recommended maximum operating junction temperature (125 °C). The power dissipated by the device is made up of two components:

  1. Output current multiplied by the input/output voltage differential: IOUT(VIN – VOUT)
  2. GND pin current multiplied by the input voltage: IGNDVIN

The GND pin current can be found using the GND Pin Current graphs in Typical Characteristics. Power dissipation is equal to the sum of the two components listed above.

The TPS73801 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions, the recommended maximum operating junction temperature is 125 °C. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered.

10.3.1 Calculating Junction Temperature

Example: Given an output voltage of 3.3 V, an input voltage range of 4 V to 6 V, an output current range of 0 mA to 500 mA, and a maximum ambient temperature of 50°C, what is the operating junction temperature?

The power dissipated by the device is equal to:

Equation 10. IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX))

where

  • IOUT(MAX) = 500 mA
  • VIN(MAX) = 6 V
  • IGND at (IOUT = 500 mA, VIN = 6 V) = 10 mA

So,

Equation 11. P = 500 mA × (6 V – 3.3 V) + 10 mA × 6 V = 1.41 W

The thermal resistance of the DCQ package is 50.5°C/W. So the junction temperature rise above ambient is approximately equal to:

Equation 12. 1.41W × 50.5°C/W = 71.2°C

The junction temperature rise can then be added to the maximum ambient temperature to find the operating junction temperature (TJ):

Equation 13. TJ = 50°C + 71.2°C = 121.2°C