UCC20225: PCB Layout Questions

Hi Jun,

Thank you for your interest in our devices.

Jun Sheng Ow said:

Q1. Should I have a connect the separated ground from primary and secondary side using a net tie so they have a common reference? If yes, will the noise couple into the primary side?

The primary and secondary side should have separate grounds to avoid any compromise of the driver's isolation.

Jun Sheng Ow said:

I'm using INA241A1 as the current sense device in my design at the same time. I dragged the differential input voltage through a slit from MCU ground to gate driver secondary ground (Motor Driver ground).
Q2. Should I avoid doing this kind of practice? or should I use isolated current sense?

I would recommend an isolated current sense to keep the MCU ground and gate driver secondary ground fully isolated. 

Regards,

Hiroki

Hi Hiroki Honda, thanks for your reply.

What if I really have to cross the differential input for current sense amplifier, does make the differential input as differential pair better than single-ended?

Hey Jun,

Our team is out of the office for the U.S. Holiday on 2/17/25. Please expect delayed responses.

Thank you,

William Moore

Hi Jun,

This connection between the primary and secondary side would compromise the isolation specifications of the device.

What bus voltage will the system's power stage have?

Regards,

Hiroki

Hi Hiroki,

The primary voltage for the gate driver is 3.3V, while the secondary voltage is 12V, as shown in the figure.

Apologies if my previous question was unclear. What I meant to ask is: Would a differential pair for the differential input voltage of the CSA be preferable to a single-ended input, considering that it has to cross the slit?

Reference article: Split Planes and What Happens When Microstrip Signals Cross Them | 2018-01-16 | Signal Integrity Journal

Thank you.

Hello Jun,

Hiroki is away from his office at the moment, he will respond within the next business day.

Regards,

Hi Jun,

Thanks for sharing the details.

The concern here is the connection between the MCU ground and the power ground.

Please correct me if I am misunderstanding the question but this connection is not recommended unless you have an isolated current sense.

Regards,

Hiroki

Hi Hiroki,

If I am not using the isolated current sense amplifier because of certain reason. Is it reasonable that I'm using differential pair rather than single-ended?

Regards,

Jun Sheng

Hi Hiroki,

Thank you for the confirmation. By the way, is there any isolated current sense amplifier having similar specification with INA241?

Thank you.

Regards,

Jun Sheng