EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: robert67 on June 13, 2017, 08:06:20 am
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Hi,
in the L200 datasheet "Absolute Maximum Ratings" section there is a
- delta Vi-o Dropout Voltage 32V
listed.
My interpretation of this: The voltage drop between input (pin 1) and output (pin 5) shall never exceed 32V.
Example:
- If the minimal output voltage is 2.85V (reference pin 4 connected to output pin 5), then the absolute maximum input voltage is 34.85V (2.85V + 32V).
- Assuming a ripple of 5V (max. 34.85V, min. 29.85V) at a given current on the input voltage, ...
- ... and a minimum dropout voltage of 2 V across the L200 between input (pin 1) and output (pin 5) ...
- ... then the maximum achievable regulated output voltage (with a voltage divider between pins 4/5) is 27.85V (29.85V - 2V).
However, there are designs using the L200 out there that seem to violate that absolute maximum rating, at least by a few volts.
So my question is: How "serious" is that absolute maximum rating? Or is my interpretation wrong?
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Dropout voltage is always the minimal input to output voltage that a regulator will operate remaining in spec.
The spec shown near the top of the first page of ST L200 datasheet is Abs. Max = 32V. This is a typo and should be read as 3.2V.
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What data sheet are you reading? Like any other linear regulator, the drop-out voltage depends on the junction temperature and current.
http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf (http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf)
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Dropout voltage is always the minimal input to output voltage that a regulator will operate remaining in spec.
The spec shown near the top of the first page of ST L200 datasheet is Abs. Max = 32V. This is a typo and should be read as 3.2V.
That explains it! A typo in the datasheet! Though I knew what the "dropout voltage" of a regulator normally is, I was convinced that they (ST) must mean something else. I couldn't fathom a "dropout voltage" of 32V.
Thank you very much!
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What data sheet are you reading? Like any other linear regulator, the drop-out voltage depends on the junction temperature and current.
http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf (http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf)
I'm reading exactly the datasheet you've linked. And on the very first page, under "Absolute Maximum Ratings", it says "Dropout Voltage" 32V!
Either that's not the "like any other" "Dropout Voltage", which I initially (and falsely) assumed (otherwise the maximum output voltage of an L200 would be 8V, with its maximum input voltage being 40V).
Or it's simply a typo in the datasheet (which Paul Price pointed out so nicely in the first reply to my post - thank you again Paul). The "like any other" "Dropout Voltage" in fact being 3.2V.
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What data sheet are you reading? Like any other linear regulator, the drop-out voltage depends on the junction temperature and current.
http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf (http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf)
I'm reading exactly the datasheet you've linked. And on the very first page, under "Absolute Maximum Ratings", it says "Dropout Voltage" 32V!
Either that's not the "like any other" "Dropout Voltage", which I initially (and falsely) assumed (otherwise the maximum output voltage of an L200 would be 8V, with its maximum input voltage being 40V).
Or it's simply a typo in the datasheet (which Paul Price pointed out so nicely in the first reply to my post - thank you again Paul). The "like any other" "Dropout Voltage" in fact being 3.2V.
Yes, it's a typo. I didn't even notice it! :palm:
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What data sheet are you reading? Like any other linear regulator, the drop-out voltage depends on the junction temperature and current.
http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf (http://www.st.com/content/ccc/resource/technical/document/datasheet/04/2c/9f/b5/65/15/49/ac/CD00000053.pdf/files/CD00000053.pdf/jcr:content/translations/en.CD00000053.pdf)
I'm reading exactly the datasheet you've linked. And on the very first page, under "Absolute Maximum Ratings", it says "Dropout Voltage" 32V!
Either that's not the "like any other" "Dropout Voltage", which I initially (and falsely) assumed (otherwise the maximum output voltage of an L200 would be 8V, with its maximum input voltage being 40V).
Or it's simply a typo in the datasheet (which Paul Price pointed out so nicely in the first reply to my post - thank you again Paul). The "like any other" "Dropout Voltage" in fact being 3.2V.
Yes, it's a typo. I didn't even notice it! :palm:
Don't worry ;D I didn't realize that either, and was going down the rabbit hole redefining "Dropout Voltage" |O