UCC3946: Driving Input with No Applied Supply

Hi Jejomar,

I believe the UCC3946 should be alright. I'll confirm that with the team and get back to you in the morning PT.

Is the costumer planning to start the watchdog pulse as the system is powering up?

Thanks for your patience,

Patrick

Hi Patrick,

Many thanks for looking into this. Our customer's system has a partial power-down mode. In the partial power-down state, the system could supply pulses to the UCC3946 WDI pin when the UCC3946 is not powered. They need to confirm that this will not cause damage to the UCC3946, and that the UCC3946 will function as expected when power is applied even if WDI is "high" at the time power is applied (no latch-up risk).

Please let me know if you need further information about our customer's use case.


Kind Regards,

Jejomar

Hi Jejomar,

Thanks for your patience in this. Has the costumer already designed the UCC3946 into their system? If not, we would strongly recommend them to consider a newer product such as the TPS3851.

Is this feasible for them?

Thanks,

Patrick

Hi Patrick,

Thank you for the recommendation. But on our customer's side unfortunately the hardware is already in mass production using the UCC3946, so using another part wouldn't be an option for them.

They have two follow-up questions:
1. Can any testing be performed by TI to assess the risk?
2. Can you help us check the product design to see if the positive clamp diode mentioned in this FAQ is present?

Kind Regards,

Jejomar

Hi Jejomar,

Thanks for your response. Perhaps they can replace the UCC3946 with the TPS3851 if they plan to do a board spin in the future.

I'll work with our team on testing the UCC3946 under the costumer's conditions and reach out about the clamp diode. I'll respond to this thread when I have that information.

Thanks,

Patrick

Hi Patrick,

I would surely relay your recommendation to the customer. We look forward to hearing back from you on the test results. Many thanks for the help!


Kind Regards,

Jejomar

Hi Jejomar,

Thanks for that. I will provide an update Tuesday Pacific Time at the latest. Unfortunately, since the UCC3946 is an old part, we don't have an evaluation module for testing it. We're looking into solutions considering that.

I'm still in communications regarding the presence of a positive clamp diode on the device.

Thanks for your patience!

Patrick

Hi Jejomar,

Thanks for your patience. Unfortunately, because it is such an old part, we don't have access to the design files. We're still looking into the design resources regarding it, though.

We're also working on obtaining samples for testing. I will update you on the status of both of these processes by Friday, Aug. 19.

Thanks,

Patrick

Hi Patrick,

Many thanks for the update! I'll share this information with the customer accordingly.


Kind Regards,

Jejomar

Thanks for your and the costumer's patience with this! The older parts typically take longer to gather resources and data on.