To prevent thermal shutdown, TJ must be less than TABS. If the
output current is very high, the power dissipation can be large. The VQFN package
has good thermal impedance. However, the PCB layout is very important. Good PCB
design can optimize heat transfer, which is absolutely essential for the long-term
reliability of the device.
- Maximize the copper coverage on the PCB to increase the thermal conductivity
of the board. The major heat-flow path from the package to the ambient is
through the copper on the PCB. Maximum copper is extremely important when
there are not any heat sinks attached to the PCB on the other side of the
board opposite the package.
- Add as many thermal vias as possible directly under the package ground pad
to optimize the thermal conductivity of the board
- Plate shut or plug and cap all thermal vias on both sides of the board to
prevent solder voids. To ensure reliability and performance, the solder
coverage must be at least 85%.