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amusin
amusin
Associate
October 5, 2008
Question

Input level voltage

  • October 5, 2008
  • 6 replies
  • 1258 views
Posted on October 05, 2008 at 11:05

Input level voltage

    This topic has been closed for replies.

    6 replies

    amusin
    amusinAuthor
    Associate
    May 17, 2011
    Posted on May 17, 2011 at 12:41

    Hi,

    There are two pairs of V_IH, V_IL defined in the datasheet on F103x6/8/B MCUs (section 5.3.12) under conditions 'TTL ports'/'CMOS ports'.

    Before I expected the only one pair V_IH/V_IL must be defined.

    Which values need to be used in different circuits?

    Thanks,

    Alex.

    lanchon
    lanchon
    Associate III
    May 17, 2011
    Posted on May 17, 2011 at 12:41

    I asked about this before and got no answer.

    amusin
    amusinAuthor
    Associate
    May 17, 2011
    Posted on May 17, 2011 at 12:41

    ST support service kept silent until I directly contacted their Russian division.

    Citing:

    First of all you don't set by SW if the pin is TTL or CMOS. On the STM32, the standard inputs are CMOS but they are TTL compliant in term of voltage threshold. Standard inputs are the pins supporting a maximum voltage of VDD+0.5V, so those which are not 5V tolerant. The FT inputs are TTL but CMOS compliant without any software configuration. So all the 5V tolerant IOs are TTL, all non 5V IOs are CMOS. However in terms of voltage tresholds(up to 3.6V for standart inpouts ) all the pins are TTL/CMOS compliant

    amusin
    amusinAuthor
    Associate
    May 17, 2011
    Posted on May 17, 2011 at 12:41

    Hi all,

    I have noticed by email (many respects to ST folks) about changes in the latest revision of the datasheet.

    So, 5.3.12 section:

    â—� For VIH:

    – if VDD is in the [2.00 V - 3.08 V] range: CMOS characteristics but TTL included

    – if VDD is in the [3.08 V - 3.60 V] range: TTL characteristics but CMOS included

    â—� For VIL:

    – if VDD is in the [2.00 V - 2.28 V] range: TTL characteristics but CMOS included

    – if VDD is in the [2.28 V - 3.60 V] range: CMOS characteristics but TTL included

    peterwrigley9
    peterwrigley9
    Associate II
    May 17, 2011
    Posted on May 17, 2011 at 12:41

    Pins with analogue alternate function are CMOS, pins without analogue alternate function are TTL.

    16-32micros
    16-32micros
    Associate III
    May 17, 2011
    Posted on May 17, 2011 at 12:41

    Hi Amusin,

    Yes, This was added in all our data-sheets to make TTL and CMOS of our I/O clear for all. Thank you for your valuable inputs ( much appreciated).

    Cheers,

    STOne-32.

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