Thermal Management

1
Thermal Management

• Must do thermal management at the device, the
  board, and the box levels
• Device proper package heat sinking
• Thermal vias to Cu planes
• Unobstructed airflow
• Soldering the device thermal pad to the PCB
• Board level
• Heat flow out of the board
• Air flow, PCB card guides, PCB with metal heat
  sinks
• Other Devices
• Other Active parts generate Heat
• Can cause localized hot-spots on PCB
  effectively reducing thermal flow and increasing
  Silicon Temp.

2
Thermal Calculations
TJC Thermal Resistance Junction to Case
(C/W) TCA Thermal Resistance Case to Ambient
(C/W) TJA Thermal Resistance Junction to
Ambient (C/W)
YJT is useful to calculate Junction
Temperature YJT is NOT a true Thermal Resistance
Only used as a Tool
Remember qCA is dependant upon package, PCB
design, and external environment. Thus, qJA can
fluctuate considerably from design to design!!!