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勝後藤.1
勝後藤.1
Associate II
March 12, 2021
Solved

About I / O static characteristics of STM32F746

  • March 12, 2021
  • 1 reply
  • 886 views

Hello,

​

All I / Os are CMOS and TTL compliant (no software configuration required).

For example, as shown in the attached document, the VOH in Table 57 has a different Min value depending on whether it is a CMOS port(a side) or a TTL port(b side).

When and which one should I choose?

​

Goto​

This topic has been closed for replies.
Best answer by waclawek.jan

It's a slightly confusing way to tell, "don't worry, no matter if you connect this output to either CMOS or TTL-level input, both will work".

At VDD=3.3V, it's guaranteed the output will be above 2.9V, which is also above 2.4V.

The numbers in that table are chose so that if you look into the respective tables for the TTL or CMOS inputs, you will see something very similar. Most users don't really think about what does that mean, what's the technology behind; they just want to see similar numbers. The output circuit is most probably better than both those values.

JW

1 reply

waclawek.jan
waclawek.janBest answer
Super User
March 12, 2021

It's a slightly confusing way to tell, "don't worry, no matter if you connect this output to either CMOS or TTL-level input, both will work".

At VDD=3.3V, it's guaranteed the output will be above 2.9V, which is also above 2.4V.

The numbers in that table are chose so that if you look into the respective tables for the TTL or CMOS inputs, you will see something very similar. Most users don't really think about what does that mean, what's the technology behind; they just want to see similar numbers. The output circuit is most probably better than both those values.

JW

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