TVS3300: Thermal Pad Connection

Kua Cha

Prodigy 50 points

Part Number: TVS3300
Other Parts Discussed in Thread: LMR51450

Dear TI Support Engineer,

I want to connect two TVS3300 back-to-back to make a bidirectional TVS. My questions are:

Can I leave the thermal pads floating?
Can I not connect the two thermal pads together? See attachment for diagram
If I also want to connect a ferrite bead to my DC line, do I place the ferrite bead before or after the TVS? See attachment for diagram

Please note that V_out in the diagram goes to the input of the buck converter LMR51450.

Thank you for your help.

Best regards,

Kua Cha

6 days ago

0 Bryan Rodriguez de San Miguel 6 days ago

TI__Expert 6940 points

Hi Kua,

Please use TVS diodes before FB. FB can sometimes raise the voltage in the line and potentially damage the diode. Electrically, you should not see any problems with leaving pad7 floating but having it connected helps spreading the transient heat. I don't see problems with connecting the gnd pins.

Best,

Bryan

0 Kua Cha 6 days ago

Prodigy 50 points

Ryan,
I am not sure if my replied email went through.

Does the answer below mean that I connect the two thermal pads together and leave them floating?

Thank you for your help.
Best regards,
Kua

0 Bryan Rodriguez de San Miguel 6 days ago in reply to Kua Cha

TI__Expert 6940 points

Hi Kua,

Why would you connect the thermal pads and then leave them floating?

Best,

Bryan

0 Kua Cha 6 days ago in reply to Bryan Rodriguez de San Miguel

Prodigy 50 points

Bryan,

I think I am a little confused. Please see my diagram and provide me feedback whether I got it right or wrong. Please note that I am trying to use two TVS3300 (unidirectional) to make a single bidirectional TVS. My question is, can I connect the thermal pad of the first TVS3300 diode to the thermal pad of the second TVS3300 diode, and then do not connect them to ground?

Again, thank you for your help.

Best regards,

Kua

0 Bryan Rodriguez de San Miguel 6 days ago in reply to Kua Cha

TI__Expert 6940 points

Hi Kua,

Please follow this app note that goes over this: link. Yes you will not see any electrical problems with not connecting the thermal pads to ground.

Best,

Bryan

0 Kua Cha 4 days ago in reply to Bryan Rodriguez de San Miguel

Prodigy 50 points

Bryan,

I have the App Note. The reason I am asking for clarification is that the App Note only shows the WCSP (BGA) version; this version does not have the thermal pad. My question is about the thermal pad. Does the thermal pad connect to GND pins (pins 1, 2, 3) internally?

0 Bryan Rodriguez de San Miguel 3 days ago in reply to Kua Cha

TI__Expert 6940 points

Hi Kua,

The thermal pad is not connected to the GND pins internally. Does this help?

Best,

Bryan

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TVS3300: Thermal Pad Connection