TIDT315 December   2022

 

  1.   Description
  2.   Features
  3.   Applications
  4. 1Test Prerequisites
    1. 1.1 Voltage and Current Requirements
    2. 1.2 Considerations
    3. 1.3 Dimensions
  5. 2Testing and Results
    1. 2.1 Efficiency Graphs
    2. 2.2 Load Regulation
    3. 2.3 Thermal Images
      1. 2.3.1 Summary
      2. 2.3.2 Images With Thermal Interface Aluminum Adapter, Then Added Heat Sink to Adapter
      3. 2.3.3 Images Without Thermal Mechanics
      4. 2.3.4 Thermal Mechanics
        1. 2.3.4.1 Summary
        2. 2.3.4.2 Description – Mechanical Setup Needs a Workshop
    4. 2.4 Bode Plot
      1. 2.4.1 Bode Plot Using Quick Start Design Tool
      2. 2.4.2 Bode Plot Using Network Analyzer
  6. 3Waveforms
    1. 3.1 Switching
      1. 3.1.1 Overview of the Four Switching Phases
      2. 3.1.2 Low-Side FET
        1. 3.1.2.1 Switch Node to GND
        2. 3.1.2.2 Low-Side FET Gate to GND
      3. 3.1.3 High-Side FET
        1. 3.1.3.1 Switch Node to VIN
        2. 3.1.3.2 High-Side FET Gate to Switch Node
    2. 3.2 Output Voltage Ripple
    3. 3.3 Input Voltage Ripple
      1. 3.3.1 Power Stage Input
      2. 3.3.2 Board Input
    4. 3.4 Load Transients
      1. 3.4.1 Load Transient 10 A to 50 A
      2. 3.4.2 Load Transient 5 A to 50 A (90 %)
    5. 3.5 Start-Up Sequence
    6. 3.6 Shutdown Sequence
  7.   A Individual Adjusting of the Rising Edge and Falling Edge With LM5143A
    1.     A.1 Both Gate Resistors Before Gate Shorted
    2.     A.2 2 × 3.32-Ω Resistors in Before Gate of the High-Side FET
    3.     A.3 2.21-Ω High and 4.75-Ω Low Resistor in Before Gate of the High-Side FET
  8.   B Thermal Behavior, Prototype in Vertical Position
    1.     B.1 Thermal Summary
    2.     B.2 Thermal Images PCB with Heat Sink and Prototype in the Vertical Position
  9.   C ON Demand – Assembly of Thermal Interface
    1.     C.1 Thermal Interface Example

B.1 Thermal Summary

Table 5-1 Hottest Spot High Side FET Q6, Maximum Temperature, 30 Minutes of Continuous Operation
Output Current Pure PCB,
no Airflow		 Pure PCB,
Airflow >0.5 m/s		 + Adapter,
no Airflow		 + Heat Sink,
Horizontal		 Heat Sink, Vertical Heat Sink,Airflow < 0.5 m/s

10 A

35.3°C

n/a

n/a

n/a

n/a

n/a

20 A

42.8°C

n/a

n/a

n/a

n/a

n/a

30 A

52.4°C

n/a

49.8°C

47.7°C

40.6°C

35.0°C

40 A

65.4°C

n/a

60.4°C

56.1°C

48.9°C

38.6°C

50 A

81.4°C

45.4°C

73.5°C

66.4°C

57.9°C

44.5°C

60 A

n/a

52.5°C

89.6°C

77.6°C

68.5°C

49.8°C
GUID-20221110-SS0I-P5HH-GTLR-GJFQTPW69RB4-low.jpg Figure 5-1 Graphical Presentation of the Hottest Spot High Side FET Q6 Table

Figure 5-1 shows at 50-A output current that any forced cooling helps most. The benefit of the adapter by itself is not significant, the PCB all alone (4 × 105-µm copper) spreads the heat reasonably and the adapter does not increase the surface. Adding the heat sink (or a metal case) increases this surface further, reduces the temperature rise - but the position for best thermal convection is important.