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UC1846-SP: Questions relating to Fabrication Process and Radiation & SEE performance.

Ashley Foxcroft71
Prodigy 35 points
Part Number: UC1846-SP
Other Parts Discussed in Thread: UC3846, , UC2846, UC1856-SP, UC1846, UC1843A-SP, UC1843B-SP, UC1843, UC1856

Hello, and before I go on, Thank you for considering the following questions:

  1. Are the UC1846-SP and UC1856-SP fabricated using any special process for radiation hardening such as SOI. Aside from the obvious packaging differences, is the Die the same as the standard versions UC2846, UC3846 etc? i.e. same Mask, same fabrication process. If not the same, then please could you explain the differences.
  2. Are the UC1846-SP and UC1856-SP recommended for new designs; how long does TI intend to continue manufacture? I can see the status is Active, but I’m looking for an answer in Years if possible.
  3. Based on the radiation performance, would TI recommend using either of these devices with a 28V Input, 5V, 1A Output?
  4. For missions that are short duration, where SEE are the main concern. Do you have any information/experience with SEE (latch-up and destructive effects) at different input voltages up to the maximum rated voltage of 40V? Is there a de-rated input voltage for a given radiation performance?
  5. Does TI plan to develop any new Radiation Tolerant step-down regulators or PWM controllers that may be a better alternative to the UC1846-SP / UC1856-SP

I look forward to your response.

  • 0
    TI__Mastermind 26055 points
    Hey Ashley,

    1. I need to gather more information. I should get a more solid answer on this monday.
    2. We don't have any plans to stop manufacturing. I don't have an answer in years, but generally as long as the product is bought we will offer it.
    3. Either of the devices will work for 28 V Input, 5V/1A output, but often why you pick a controller is based on topology. Is there a topology preference?
    4. All radiation data that we have in compiled in the Radiation and Reliability reports in the technical documents section.
    5. We have a plan to make new radiation tolerant PWM controllers, but again that will be dependent on topology.

    Thanks,
    Daniel
  • 0 in reply to Daniel Hartung
    Prodigy 35 points
    Hi Daniel

    I do not have a strong preference for topology and isolation is not a requirement. The main reason for selecting the UC1846 is the 40V Abs Max I/P which seemed like a sensible choice for a 28V +/-6V Input. I am working on a UC1846 based Buck converter; I wanted to avoid a custom transformer. I would consider other typologies depending on the new RT PWM controller (Re: Point 5).

    Best regards. Ashley
  • 0 in reply to Ashley Foxcroft71
    TI__Mastermind 26055 points
    Hey Ashley,

    We have a UC1843B-SP coming out that will be similar to the UC1843A-SP but with higher radiation performance. You will need a discrete high side driver, but you would need one for the UC1846-SP anyway. The Abs max of the UC1843A-SP is 30 V, but this is only from a low impedance source. A resistor that will limit the current will work as there is a Zener Diode that will limit the voltage.

    Did you pick the UC1846-SP for the fact it has two outputs or is one output fine?
    The UC1843A-SP will only have one output.

    Thanks,
    Daniel
  • 0 in reply to Daniel Hartung
    Prodigy 35 points

    Hi Daniel

    For the UC1846, I am only using one output (B) and so I am not using a high side driver. So, one output is fine.

    If you accept my 'friend request' (lol, what is this, Facebook!) I could send you a schematic, but I unfortunately I cannot post this publicly, against company policy. 

    I see how the UC1843 can be used for high input voltages (so thanks for the suggestion), but it still requires a transformer with Aux winding to provide Vcc. Since my application requires a 28V (nominal) dc input with some small variation due to surge conditions, for a 30V max Vcc, I would consider using a separate discrete linear regulator to regulate Vcc to around 24V. For a number of reasons, I'm trying to avoid using a transformer. 

    I think the UC1846 or UC1856 is still a good choice even if i'm only using one output for a Buck converter. The 40V Abs Max Input should be adequate given that we will have input filtering and transient protection. 

    Thanks again, Ashley

  • 0 in reply to Ashley Foxcroft71
    TI__Mastermind 26055 points

    Hey Ashley,

    Generally when you guys send stuff to us we do it through email then.

    It is important to note while the UC1843 does not actually require an Aux winding it will be more efficient with one.

    The Aux winding is generally just used for efficiency reasons.

    If you don't need improved radiation with the B version we will come out with, the UC1846 sounds like the best option for you.

    Thanks,

    Daniel

    P.S. if you will want to talk about it and send me the schematic I can contact you through email.