Re: Question Vinh/l+, Vinh/l-

Hello Christian:

Some specifications for Schmitt trigger (or hysteresis) inputs
give values in terms of Vt+ for the high threshold value and
Vt- for a low threshold value.

One old example is the 74XXX132 series of devices.

The Texas Instruments TTL Logic data book gives min, typ and
max Vt+ and min, typ, and max Vt- values and defines them as
Positive-Going Threshold Voltage Vt+ and Negative-Going Threshold
Voltage Vt-

From BIRD39 the following diagram illustrates how the hysteresis
subparameters are defined:

         ^
     O | +-------+----<----+--------+------------
     U | ! ! ! !
     T | ! ! ! !
     P | ! ! ! !
     U | ! ! ! !
     T | ! ! ! !
         | v v ^ ^
     V | ! ! ! !
     O | ! ! ! !
     L | ! ! ! !
     T | ! ! ! !
     T | ! ! ! !
     A | ! ! ! !
     G | ! ! ! !
     E | -----------+-------+---->----+--------+
         |_____________________________________________________________>
                     Vinl- Vinl+ Vinh- Vinh+
                           INPUT VOLTAGE

IBIS Version 3.2 relates the Vt+ and Vt- min and max values that may
appear in data books as follows:

| Vinh+ Hysteresis threshold high max Vt+
| Vinh- Hysteresis threshold high min Vt+
| Vinl+ Hysteresis threshold low max Vt-
| Vinl- Hysteresis threshold low min Vt-

Whether or not the data book uses the Vt+ and Vt- terminology, the
hysteresis or Schmitt trigger inputs should be entered consistent
with the figure above.

Best Regards,
Bob Ross
Mentor Graphics

Sporrer cad52 wrote:
>
> Hi,
>
> I am from Infineon Technolgies AG, Munich (former Siemens
> Semiconductor) and responsible for the generation of IBIS
> models for our IO-cell libraries.
>
> For IBIS 3.x I have a problem with the meaning of Vinh+,
> Vinh-, Vinl+ and Vinl- subparameters inside the
> [Model Spec] Keyword.
> What is the difference between Vinh/l+ and Vinh/l- ?
> What is the meaning of Vt+/Vt- ?
>
> Process, temperature and voltage variation is considered
> in the typ, min and max columns. But what kind of
> variation must be done to get different Vin(h+-)/(l+-)
> values?
>
> I hope somebody can help me.
>
> Thanks Christian.
>
> Christian Sporrer
> Infineon Technologies Munich
> Email: Christian.Sporrer@infineon.com
> Tel: +49 89 234 24069
> Fax: +49 89 234 28555
Received on Tue Jun 15 17:58:59 1999