SLVS719G June   2008  – January 2015 TL1963A

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Overload Recovery
      2. 9.3.2 Output Voltage Noise
      3. 9.3.3 Protection Features
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Output Capacitance and Transient Response
    2. 10.2 Typical Applications
      1. 10.2.1 Adjustable Output Operation
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Fixed Operation
        3. 10.2.1.3 Application Curve
      2. 10.2.2 Paralleling Regulators for Higher Output Current
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
        3. 10.2.2.3 Application Curve
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Considerations
      1. 12.3.1 Calculating Junction Temperature
  13. 13Device and Documentation Support
    1. 13.1 Related Links
    2. 13.2 Trademarks
    3. 13.3 Electrostatic Discharge Caution
    4. 13.4 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

12 Layout

12.1 Layout Guidelines

  • For best performance, all traces should be as short as possible.
  • Use wide traces for IN, OUT, and GND to minimize the parasitic electrical effects.
  • 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.
  • Place the Output Capacitor as close as possible to the OUT pin of the device.
  • The tab of the DCQ package should be connected to ground.
  • The exposed thermal pad of the KTT package should be connected to a wide ground plane for effective heat dissipation.

12.2 Layout Example

layoutexto263_slvs719.gifFigure 36. TO-263 Layout Example (KTT)
SOT223DCQ2.gifFigure 37. 6SOT-223 Layout Example (DCQ)
layout3_slvs719.gifFigure 38. 4SOT-223 Layout Example (DCY)

12.3 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:

  • Output current multiplied by the input/output voltage differential: IOUT(VIN – VOUT)
  • 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 TL1963A-xx 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.

For surface-mount devices, heat sinking is accomplished by using the heat-spreading capabilities of the PC board and its copper traces. Copper board stiffeners and plated through-holes can also be used to spread the heat generated by power devices.

Table 4 lists thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 1/16" FR-4 board with 1-oz copper.

Table 4. Thermal Data for KTT Package (5-Pin TO-263)

COPPER AREA BOARD AREA THERMAL RESISTANCE
(JUNCTION TO AMBIENT)
TOPSIDE(1) BACKSIDE
2500 mm2 2500 mm2 2500 mm2 23°C/W
1000 mm2 2500 mm2 2500 mm2 25°C/W
125 mm2 2500 mm2 2500 mm2 33°C/W
(1) Device is mounted on topside.

12.3.1 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 14. 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 15. P = 500 mA × (6 V – 3.3 V) + 10 mA × 6 V = 1.41 W

Using a KTT package, the thermal resistance is in the range of 23°C/W to 33°C/W, depending on the copper area. So the junction temperature rise above ambient is approximately equal to:

Equation 16. 1.41 W × 28°C/W = 39.5°C

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

Equation 17. TJ = 50°C + 39.5°C = 89.5°C