TMP1075: Exposed pad connection of TMP1075DSG package

Murali Malla

Part Number: TMP1075

Hi,

I'm thinking if using TMP1075DSG (2mmx 2mm) package in my design and I have a question regaring its exposed pad conenction.

In my design, TMP1075DSG is used to sense the temperature of a copper plane which is covered with solder mask and the copper plane is not at ground potenetial. The copper plane with solder mask will be between 0.5V to 2.5V.

The datsheet of TMP1075 shows exposed pad conenction to ground plane and ground plane is mentioned as "heat source". This is different from my application where heat source is not ground.

May I know your recommendation on how to connect TMP1075DSG exposed pad in my application? Can I leave it floating or does it need to be grounded? If I leave it floating, would it still sense the underneath copper plane temperature eventhough the copper plane has solder mask?

5 months ago

0 HarryG 5 months ago

TI__Expert 7190 points

Hello Murali,

Connecting the TMP1075's thermal pad to your copper plane could thermally couple the sensor to the board since copper planes tend to absorb heat generated across a PCB. Unless your intention is to use the temperature sensor to monitor the board's temperature, I would recommend leaving the pad floating.

Regards,

Harry

0 Murali Malla 5 months ago in reply to HarryG

Prodigy 10 points

Thanks for your response. Intention here is to sense board temperature. So, connecting the TMP1075's exposed pad to the copper plane on board makes sense. But the concern I have is the copper plane will not be at ground potential; it will be between 0.5V to 2V. Could you confirm if it is ok to connect the TMP1075's exposed pad to positive potential nod instead of ground? If is not allowed (because of ESD structures and other stuff), can I leave it floating?

0 HarryG 5 months ago in reply to Murali Malla

TI__Expert 7190 points

Hello Murali,

I would not recommend soldering to the copper plane if it has an active voltage across it. Is that the only copper plane in the board design or is there another reserved for ground signals?

Regards,

Harry

0 Murali Malla 5 months ago in reply to HarryG

Prodigy 10 points

That is the only copper plane which gets hot and hence I want to measure it with TMP1075.

0 HarryG 5 months ago in reply to Murali Malla

TI__Expert 7190 points

Understood, let me check with our design team if there are any implications with soldering the thermal pad to a plane with some voltage potential and will get back to you tomorrow.

Regards,

Harry

0 Murali Malla 5 months ago in reply to HarryG

Prodigy 10 points

Hi Harry,

May I know if you have any update?

0 HarryG 5 months ago in reply to Murali Malla

TI__Expert 7190 points

Hello Murali,

Thanks for your patience while I looked into this. Based on information from our backend team, it is not recommended to solder the TMP1075 to any copper plane that isn't connected to ground.

Regards,

Harry

0 Murali Malla 5 months ago in reply to HarryG

Prodigy 10 points

May I know the reason? Is exposed pad "shorted" to ground pin internal to the TMP1075 or is there any ESD diode between exposed pad and ground pin?

0 HarryG 4 months ago in reply to Murali Malla

TI__Expert 7190 points

Hello Murali,

It's not recommended to solder the thermal pad to anything but ground because there is a potential conductive path between the thermal pad and the die inside the package.

Regards,

Harry

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TMP1075: Exposed pad connection of TMP1075DSG package