MC33078: MC33078DR burn issue

Hello William,

I don't see any obvious problems in the schematic. Do you have the reel packaging label? 

Attached photo

William,

I will forward this to quality. I should have a reply by end of this week.

What stress is used as a part of the "burn in" process?

Hi Ron, 

The burn in process only turn on power , input music  , check sound out normal then let it sit for 8 hours.

I measured the waveforms of every point and found that there was "over shooting" reaching 8V on net#+5VA during power on.as below photo

When I remove the protect diode(D14/D19/D17/D22/D26/D40/D38/D41), the over shooting disappeared.

The stress seems to be generated by #MC33078
I can't understand how this over shooting came about? I don't know if it is related to the #MC33078 burned?

William,

I expect that +12V precedes the -12V and op amp outputs initially go high. This is due to supply voltages and input common mode range during the power up.

The 5V overshoot is not a problem for MC33078, but it may be a problem for computer U3.

William,

How many samples have failed like this?

Hi Ron,

There are two samples have failed.

William,

If you believe this may be a MC33078 related issue, you can follow the path below. Always refence a data sheet specification, ICC supply current is the obvious one.  

• For requests concerning suspect non-conforming TI material to visit TI portal for Customer Product Return (CPR): www.ti.com/support-quality/resources/customer-returns.html and to follow TI guidelines for returns www.ti.com/lit/sprac01.