Is there a Schmitt trigger in ST7Lite19??

marcosarti29 · ‎2005-10-19

Posted on October 19, 2005 at 10:46

marcosarti29 · ‎2005-10-19

Posted on October 19, 2005 at 09:25

Hi,

i use ST7Lite19F in my application.

The pins of PortB are in floating input with RC (filtre) very high: 47K x 47pF beacause there is a lot of noise in the room..

Question: the ST7Lite19F have a Schmitt trigger in input? What's maximun value of my RC that i can use it?

Is there an application note with specification?

Thanks.

marcosarti29 · ‎2005-10-19

Posted on October 19, 2005 at 10:16

Sorry,

47nF not 47pF!

laurent239955_stm1 · ‎2005-10-19

Posted on October 19, 2005 at 10:44

Hi,

There is a schmitt trigger on each I/O pin (cf fig 30 in datasheet).

There is no recommendations about RC value, but take care that your filter introduces a delay.

Hope this help.

Laurent

fggnrc · ‎2005-10-19

Posted on October 19, 2005 at 10:46

According to the datasheet (page 105 - 13.8.1 General characteristics), the Schmitt trigger hysteresis is tipically 400 mV.

As for the maximum RC value, you have to consider the input current leakage which can be 200 uA if the input is floating.

Bye

EtaPhi