This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Issue with old Stellaris LM3S1968-IQC design

Other Parts Discussed in Thread: LM3S1968

Hi,

I have been asked to post here in an email from the support email asktexas@ti.com - please move/advise if there is a better place to ask this question. It's about a NRND Stellaris MCU.

I have recently inherited a design at a new company and there is an issue I'm debugging where a LM3S1968-IQC sometimes fails (goes to an almost dead short and starts to draw 0.5A on the 3V3 rail, never to work again) on power-up. I think I have tracked this down to an incorrect capacitor value used in the design, but wanted to check if my reasoning seemed valid.
The capacitor in question is the bulk decoupling for the core voltage provided by the internal LDO. The application note/datasheet suggest between 1 and 3uF but a 10uF Tantalum capacitor was used instead. Taking into account the tolerance of the capacitor, this could, on some boards, lead to about 10x the charge that was specified - on start-up this might well overload the LDO. Could this potentially be causing the failure we see?

Many thanks

Charlie