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REG1117: expected temperature drift and comparable parts

Part Number: REG1117
Other Parts Discussed in Thread: LM1117, , REF3030

Hi there,

i have questions regarding comparing temperature drifts (expectation due to datasheet Infos) of different fixed 3.3V linear Regulators.

My main Parameters are Iout= 25mA, Vin= 6V

The first one basically is, is the temperature drift which is to be expected in the range of ~0°C to 80°C better, worse or the same for RE1117-3.3 compared to LM1117IMPX-3.3?

The initial accuracy is not so important, due to the fact that it is calibrated away at first (when units are shipped out), for me the intereting part is the change from/of that value.

If there is by design a difference, what's the explanation behind, the Technology which is used?

As i understand it the LM1117 is a zener trimmed bandgap reference, according to the firstpage of the datasheet.

The REG1117 doesn't say this "by text", but if i compare the functional block diagrams there are a lot of similarities.

When i compare via the Price i can see that LM1117IMPX-3.3 costs on ti.com 0.38, compared to 0.92 for REG1117-3.3 (same package).

Where does the price difference come from, the trimming of REG1117?

Does this trimmming influence the voltage drift?

Does figure 6 of LM1117 datasheet Show "the same thing" as REG1117 datasheet page 7 bottom left graph?

Is there something like an overview/comparison of different Regulators (preferably fixed 3.3V) which is showing (initial) accuracy, temperature influence and such?

Many questions, i know, but if anybody can shine a light on at least some aspects, that would be great.

Have a nice day. BR Michael

  • Please excuse a delay in response due to the US Holiday.

    Very Respectfully,
    Ryan
  • No worries,

    happy 4th of july.

    BR Michael

  • Hi Michael,

    These particular regulators were originally designed by different companies which have since been acquired by TI. As shown in the REG1117 datasheet it was originally released by Burr-Brown. LM1117 was originally released by National Semiconductor. The temperature drift for REG1117 is slightly better over 0 to 80C. This information is shown in figure 6 of LM1117 and the bottom left curve of REG1117. The REG1117 also has a better transient response.

    Very Respectfully,
    Ryan
  • Hi Ryan,

    yes, that's all clear to me as i basically wrote all this in my initial post.
    I don't want to sound to harsh, i know i somethimes do, additionally as i'm new in this Forum to, but that's not an answer i'm happy with to be honest.

    I really need to know more on this whole temperature drift topic and understand more on how to "read" the datasheets information regarding it. What can i expect from the graphs, which technology should be used/preferred, which technology does provide the smallest spread (drift wise) by design, etc.

    I really hope somebody can help me on this questions because i need to be sure (as close as i can get) how much the actual parts deviate from the typical value. That's my goal at the end, to really estimate what the spread will be and not only typically.

    I believe it's not easy to say, but i guess there is information which will help me to come closer to the truth and not just expect that each part manufactured follows the typical value.

    Thanks anyway for your reply,
    Best regards,
    Michael
  • Hi again,

    hmmm, so it seems nobody is abler to help me on that.

    Beside that, can somebody at least help me on that question, it arised when i searched the forums a Little:

    See thread: REF3030: temperature drift correlation

    I wrote there

    Dear Diego,

    sorry for highjacking this topic/discussion, but may i ask you on this:

    The temperature coefficient is determined using a box method, therefore the max could appear at any temperature.

    While most parts will have a similar shape, we do not guarantee that the max will be at any specific temperature.


    Is this true for temperature drift information of LDOs too? I mean the background to it beeing the method used?

    And additionally, is it true for basically all temperature drift data f.e. for amplifiers also?

    Thanks in advance, best regards

    Michael

    And got that answer:

    Hi Michael,

    I'll answer this in place for Diego. From my understanding that is true because if it's not a EC spec then its typical and not guaranteed. But for more accurate answer or confirmation, I would suggest you to ask this in the LDO subforum.

    -MZ

    ----------------

    So, i'm asking for an statement regarding the underlined sentence and additionally why that is the case, in easy words.

    I hope somebody is able to answer me that.

    Best regards Michael

  • Hi Michael,

    Something very similar to the box method is used for most LDO testing and as MZ in the other forum mentioned it doesn't guarantee that the maximum or minimum will occur at any specific temperature. Now, that being said most LDO's use a bandgap reference and have a Vout drift that looks like a parabola which is pointing down, y=-(x^2), and peaks somewhere around 60C and 85C. However, there are some older devices which use a Zener reference and the temp drift on those tends to look more like a sine wave (starts low, increases, decreases, and then increases)

    As MZ alluded to the devices in a particular family will have a very similar shape however, we don't test parts in such a way that can guarantee the shape or where the maximums/minimums occur. In general since our LDOs are power management products they are usually used in applications where accuracy over all conditions is more important than the accuracy at any specific point (Temp, Vin, Iout, etc...) so our tests are directed at overall accuracy. 

    As for the applicability of this to other products, the references should have similar drift shapes if we are talking about parts that use the same type of reference (bandgap, Zener, etc...). However, they may have different tests or data that is available since the use cases for the products are so different. 

    I hope that helps you understand the factors involved a bit more. 

    -Kyle

  • Hi Kyle,

    thanks for your answer as well.

    Best regards Michael