LMR36503-Q1: FMD Clarification

Andy Snawerdt

Intellectual 1780 points

Part Number: LMR36503-Q1
Other Parts Discussed in Thread: LMR36506

Hi Team,

My customer has a couple of questions about some of the failure modes for this device.

For the "Gate driver stuck on failure mode". Is this stating that the device cannot switch and there will be no regulated output? Since the GD is stuck on, would we just expect to see Vout = ~Vin under this failure mode?
Will a short between "BOOT" and "VCC" cause a thermal event? The pin FMA below states that damage will occur. Would like to better understand what kind of damage could occur as thermal events are a sever issue based on our safety goals.

Thanks!

Andy

over 2 years ago

+1 Andrew Kutzler over 2 years ago

TI__Genius 15380 points

Hi Andy,

For #1, your assumption is correct. Vout = Vin, as the high side FET cannot turn itself off. You could run into some thermal event issues depending on how the output load behaves when Vout is too high, and the FET is forced to output current.

For #2, The VCC LDO will pop causing the device to most likely not function. It could potentially heat up, but these newer devices like LMR36506 are quite good at turning themselves off before any crazy damage occurs. The device even has it's own shutdown mechanism if it heats up too much.