Other Parts Discussed in Thread: LMQ61460,
We have a design generating +5V @ 4A and +3.3V @ 4A using two off LMQ61460 over -40'C to +85'C with 10V to 30V input range.
Both supplies were designed using Webbench, running at approximately 600kHz, with turn on being about 9V. They worked fine on PCB. Design(s) stay "cool" even when both supplies are loaded to 4A, no thermal or regulation issues are seen. They are on a 4 layer PCB, with careful layout of high current tracks/planes, almost copying the PCB layout example in the data sheet.
However upon testing at low temperatures less than -20'C (initially with full 4A loads), when input voltage was applied (from a current limited supply) both regulators "blew" and short circuited. This was repeated twice just in case was a fluke.
This has just been repeated, now with virtually zero loading on 5V and 3.3V supplies (30mA odd) and was OK at -20'C with 10V and 30V input, but at -40'C with 30V input both LMQ61460 devices have gone short circuit.
Both regulators have EMI pre-filters, as designed buy webbench, as well as all the relevant smoothing/filter capacitors.
Below is the +5V supply design. 3.3V PSU is similar.
Any thoughts on why these devices (both 5V and 3.V) are "blowing" at low temperature ?