OPA551: Question about OPA551 thermal information of section 6.4

Kazuya Nakai59

Guru 21705 points

Part Number: OPA551

Hello guys,

One of my customers is considering using OPA551 for their new products.

They have a few questions about OPA551 as the follows. Could you please give me your reply?

Q1. The device datasheet (Version SBOS100B) says that RthetaJA of KTW(DDPAK/TO-263) is 22.7 degree /W in section 6.4.

Also it says that RthetaJA of KTW(DDPAK/TO-263) is 65 degree /W in section 10.3 . power dissipation.

Which is thermal information correct?

Q2. In 10.2 Layout Example section, PDIP-8 NC pins are connected to GND.

Is this no problem? Is this correct?

Your reply would be much appreciated.

Best regards,

Kazuya.

over 4 years ago

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi Kazuya,

I think the lower value is valid with heatsinking and the higher value without heatsinking. See figure 38 of datasheet.

"NC" means "no internal connection". Connecting "NC" pins as shown could slightly enhance the cooling.

Kai

0 Raymond Zhang1 over 4 years ago in reply to kai klaas69

TI__Guru* 77541 points

Hi Kazuya-san

Q1: Which is thermal information correct?

Both figures are likely to be correct.

I am attaching an application report regarding on the topic. Your application is likely using heat sink in this part, so it is recommended to use 34.7C/W from RthetaJC(top) figure from the section 6.4, see the attached image.

https://www.ti.com/lit/an/slua844b/slua844b.pdf?ts=1619201274318&ref_url=https%253A%252F%252Fwww.google.com%252F

Q2. In 10.2 Layout Example section, PDIP-8 NC pins are connected to GND.

NC pin may be connected to ground as Kai suggested or you can be left floating. I would connect it to ground.

Best,

Raymond

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OPA551: Question about OPA551 thermal information of section 6.4