DRV8350: Capacitor on VGLS pin

Hey Brian,

Brian Wang0928 said:

Customer found that when capacitor on the VGLS pin is changed from 1uF to 4.7uF. That VGLS pin can be damaged. There're two failure units after operating with 4.7uF at VGLS pin in customer side. It looks it's 100% fail with this 4.7uF cap setting. 

Was anything else changed/were there damages even before this? This seems unlikely that just changing local bulk will haer this effect/ VGLS is the supply for the low side gates.

Does the customer have waveforms of VM, GLx, SHx, VGLS before and after the change?

Brian Wang0928 said:

The reason behind why customer use 4.7uF at VGLS pin, because it could keep the Vvcp > 10V.  

So the issue is with VCP voltage not VGLS? VGLS is LS supply VCP is HS supply so if there is issue with VCP then we should focus on that one not VGLS. Please confirm.

Best,

Akshay

Hello Akshay,

Previously, when using the DRV8350S with a 4.7µF capacitor on VGLS while outputting current, a "VGS_LB" error was triggered. At that time, the measured VGLS voltage level was abnormal (only around 2 to 3V). Please refer to the waveform below.
What could be the possible causes for damage to VGLS? Thanks

Hey Ke,

Previously, when using the DRV8350S with a 4.7µF capacitor on VGLS while outputting current, a "VGS_LB" error was triggered

What was the reason for moving to 4.7uf? It seems the damage only happened after moving to 4.7uF based on the statements above. It this correct? Or were there other issues before moving to 4.7uF?

If you do an ABA swap with a new DRV IC will the problem go away? I am more likely to suspect a switching transient on SHx, GLX, or SLx coupling to VGLS damage or VM transient coupling to VGLS. But I need more info on the history of what was observed before the VGLS damage to think of potential causes for damage.

Did you notice any transients/abs max violations on the signals mentioned above when collecting switching waveforms?

Best,

Akshay