FDA802A PIN33 NC connected to GND

[Lucas Sun]

Hi friends from ST,

Is there any description or comment for FDA802A PIN33, I found this pin doesn’t connect to GND like other NC PINs.

I am analyzing FDA802A-VYT VCC PIN damaged on China local AMP, and found PIN33 was connected to GND by the previous engineer. (But this pin is float in ST application.)

Can this PIN connect to GND cause this damage issue? I have contacted the local FAE from ST in Shanghai, and they knew nothing.

 

[Peter BENSCH]

Welcome ​@Lucas Sun, to the community!

The FDA802A is a two-channel Class-D amp and the little brother of the four-channel FDA801/FDA801B. The latter has on pin 33 one of the two positive output pins of the third channel, which is not present on the FDA802A. Otherwise, the pin layout is largely pin-compatible, so in principle, depending on the requirements, both amplifier variants can be implemented with the same layout.

DB4820 lists pin 33 as N.C. = Not Connected, so you can assume that the pin on the FDA802A is indeed unconnected and that you can also tie it to GND. You are welcome to verify this for safety, though, and try measuring a simple diode path between pin 33 and one of the GND and VCC pins with both polarities, which should not produce any result in any case. However, in connecting pin 33 to GND you lose the option of also fitting an FDA801/B to the same layout.

Hope that helps?

Regards
/Peter

[Lucas Sun]

Hi Peter,

Thanks for your reply.

I have a call with China local FAE today and they told me PIN33 is internal used pin that can’t not connect to GND .

But in your comment, PIN33 can be float according to ST application or connected to GND, right? In ST application, PIN33 is float, so I think there is special function for FDA802A.

[Peter BENSCH]

Since my Chinese colleague is more deeply knowledgeable in the subject and is certainly right, you should probably leave pin 33 floating and connect it to nothing.

Regards
/Peter