Hi,
My customer has started circuit design and has question about NC pin (#17).
In the datasheet, it's described that NC pin can be either left open or connecting to GND and it's left open in typical application drawing(left).
On the other hand, if I check the schematics of EVM, it's connected to GND.
From performance and/or safety perspective, which is "better" or recommended?
Also, is this pin internally unconnected?
Thank you for your support in advance.
Regards,
Ken
Hi, Ken,
Good to hear from you!
Pin 17 is truly "NC," there is no wire bond inside the device on this pin. For ease of layout, and better thermal performance, best practice is to connect this terminal to the SOURCE pins on the device (which are "ground" on the EVM). If you look at the EVM top copper plane, this makes it very easy - you have one pour for the SOURCE pins 12-16, and 18-23, and tie in pin 17 (as well as pin 24 since the SOURCE is "grounded").
I put "ground" in quotes as the high-side device on the EVM has an isolated ground, which is different than earth ground. It is called "ISO_RET_H" on the schematic. This is actually the switching node of the half-H-bridge output. This is the point called, "VSW" in Figure 1.
I hope this is clear. If not, let me know, and I will try to explain further.
