UCC14241-Q1: VEEA Routing and Connection to the General VEE Plane

Kartavya Agarwal

Part Number: UCC14241-Q1

Tool/software:

Hi,

I have a question regarding the routing of the VEEA node (pin 35) relative to the general VEE plane.

Under Section 12.5.1 in the datasheet (page 46), it is recommended that "VEEA (pin 35) should be isolated through all PCB layers, from the VEE plane as shown in the red box below."

Does this mean that we should avoid any connection between VEEA and the VEE plane on the PCB? This would mean that there is no single point conenction between VEE and VEEA on the PCB (external to the IC)?

Is this because VEEA is internally connected to VEE within the IC?

We are a bit confused by the conflicting recommendation in this section and the pin configuration table. Could you please provide any advice or tips on managing this aspect of the design?

4 months ago

+1 Steven Mappus1 4 months ago

TI__Mastermind 32975 points

Yes, you should make a direct connection between the lower FBVDD/FBVEE resistors/capacitors and this is because the internal FB comparators are referenced to VEEA and we want to avoid coupling VEE switching noise into the FB comparators in order to maintain a high degree of voltage regulation accuracy. Pin 36 is VEE and pin 35 is VEEA and from the Figure 12-20 in the UCC14241 data sheet you can see that the external, single point connection is made by connecting pin 35 to pin 36, which are still connected into the VEE plane but also somewhat "isolated" by the single via shown in the red outline. That single via doesn't connect to any of the internal or bottom side VEE planes but only connects to a track that makes a direct route to the lower FB resistors/capacitors so that the lower FB resistors/capacitors are not thoughtlessly connected into the large VEE plane.