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The text values in the specifications section are always the real specs. Unless otherwise stated (and that's quite rare), graphs are suggested values, typical ranges, variations due to a single va...
Answer
#2: Post edited
by
Olin Lathrop
·
2021-01-12T22:57:38Z (almost 4 years ago)
- The text values in the specifications section are always the real specs. Unless otherwise stated (and that's quite rare), graphs are suggested values, typical ranges, variations due to a single variable, and the like. They are NOT specifications.
- The only accuracy you can count on is what it says in the <i>Static Characteristics</i> section of the datasheet that you quoted: ±1 °C from -25 °C to 100 °C, and ±2 °C from -55 °C to 125 °C. This is over the 2.7 V to 5.5 V supply range.
- Note that there are several variables here effecting the offset of the reading from the true temperature. Three obvious one are part to part variation, temperature, and supply voltage.
- The labeling for the graph you showed could be better, but it seems to be trying to show the <i>typical</i> variation as a function of temperature alone. Remember, THIS IS NOT A SPEC. It's more a rough guidance to give you some feeling for the tradeoffs.
- It is interesting that they show the supply voltage range as 2.8 V to 5.5 V, which eliminates the lowest 100 mV of the recommended supply range. Perhaps the 2.7 to 2.8 V supply range is really pushing the limits, and eliminating that reduces errors as a function of temperature.
- I also interpret that graph as implying that while the supply voltage is somewhere within the stated range, it is held constant for the purpose of the graph.
- <h3>Summary</h3>
- The text gives you the real spec worst case error.
- The one graph you quoted says that
- <b>if</b>:
- 1 - You hold the supply voltage constant somewhere from 2.8 to 5.5 V.
- And
- 2 - For a single part.
- <b>Then</b>
- Here is the <i>typical variation</i> of the error as a function of temperature alone.
- The text values in the specifications section are always the real specs. Unless otherwise stated (and that's quite rare), graphs are suggested values, typical ranges, variations due to a single variable, and the like. They are NOT specifications.
- The only accuracy you can count on is what it says in the <i>Static Characteristics</i> section of the datasheet that you quoted: ±1 °C from -25 °C to 100 °C, and ±2 °C from -55 °C to 125 °C. This is over the 2.7 V to 5.5 V supply range.
- Note that there are several variables here effecting the offset of the reading from the true temperature. Three obvious one are part to part variation, temperature, and supply voltage.
- The labeling for the graph you showed could be better, but it seems to be trying to show the <i>typical</i> variation as a function of temperature alone. Remember, THIS IS NOT A SPEC. It's more a rough guidance to give you some feeling for the tradeoffs.
- It is interesting that they show the supply voltage range as 2.8 V to 5.5 V, which eliminates the lowest 100 mV of the recommended supply range. Perhaps the 2.7 to 2.8 V supply range is really pushing the limits, and eliminating that reduces errors as a function of temperature.
- I also interpret that graph as implying that while the supply voltage is somewhere within the stated range, it is held constant for the purpose of the graph.
- <h3>Summary</h3>
- The text gives you the real spec worst case error.
- The one graph you quoted says that
- <b>if</b>:
- 1 - You hold the supply voltage constant somewhere from 2.8 to 5.5 V.
- And
- 2 - For a single part.
- <b>Then</b>
- Here is the <i>typical variation</i> of the error as a function of temperature alone.
- <hr>
- <blockquote>These answers are to me as unclear as the datasheet is.</blockquote>
- It can seem that way because they contain too much babble. Only the very last sentence matters and clearly states what is going on is:
- <h3>"What you can see in Figure 24 are the typical values, max values can go up to +/-1C range."</h3>
- In other words, ±1 °C is the error you have to design to. Everything else might give you some intuition, but is ultimately irrelevant.
#1: Initial revision
by
Olin Lathrop
·
2021-01-11T14:52:03Z (almost 4 years ago)
The text values in the specifications section are always the real specs. Unless otherwise stated (and that's quite rare), graphs are suggested values, typical ranges, variations due to a single variable, and the like. They are NOT specifications. The only accuracy you can count on is what it says in the <i>Static Characteristics</i> section of the datasheet that you quoted: ±1 °C from -25 °C to 100 °C, and ±2 °C from -55 °C to 125 °C. This is over the 2.7 V to 5.5 V supply range. Note that there are several variables here effecting the offset of the reading from the true temperature. Three obvious one are part to part variation, temperature, and supply voltage. The labeling for the graph you showed could be better, but it seems to be trying to show the <i>typical</i> variation as a function of temperature alone. Remember, THIS IS NOT A SPEC. It's more a rough guidance to give you some feeling for the tradeoffs. It is interesting that they show the supply voltage range as 2.8 V to 5.5 V, which eliminates the lowest 100 mV of the recommended supply range. Perhaps the 2.7 to 2.8 V supply range is really pushing the limits, and eliminating that reduces errors as a function of temperature. I also interpret that graph as implying that while the supply voltage is somewhere within the stated range, it is held constant for the purpose of the graph. <h3>Summary</h3> The text gives you the real spec worst case error. The one graph you quoted says that <b>if</b>: 1 - You hold the supply voltage constant somewhere from 2.8 to 5.5 V. And 2 - For a single part. <b>Then</b> Here is the <i>typical variation</i> of the error as a function of temperature alone.