Other Parts Discussed in Thread: TPS54620
Hi,
Posting this q on behalf of my customer. Please follow-up via e-mail for a Webench schematic.
We have an existing design that uses TPS54620. In the latest build we have replaced TPS54620 with TPS54521 since the design was only consuming 3A.
I understand that there is a 5% efficiency penalty and 25oC reduction in Absolute maximum junction temp.
However, out of 3 boards that were tested at 70oC ambient , we found that one was damaged. The HS fet was shorted causing 12V to 3v3 short and taking down rest of the board.
We are investigating what could have caused the issue, and to ensure that the design is still meets the requirements for TPS54521.
Following steps were done
- Thermocouple on the Top case shows at 70C ambient max case temp of 89 oC (Assuming ψJT of 0.5C/W, TJunction = 89+ 0.5*1.5 = 89.75) sluu484
- The SW node voltage looks typical measured at 500MHz bw . We could not see any signs of OV stress
- Minimal overshoot of max14V
- -0.7V undershoot during body diode conduction with HF spike of -1V
When using TPS5421, what is the dead time guaranteed by the chip over temp range?
