anyone know about TTL?

[louislu]

hello...TTL is one of the buffer type.it is a input pin for my chip.but i donno wat is TTL...and what is it used for?do i need to take care of it when connecting my circuit...thanks

 

[tavib]

:lol:
A TTL input is an input compatible with TTL family. A TTL input will consider a "0" logic if voltage on it is in range of 0...0.8V and will consider a "1" logic if voltage on it is in range of 2...5V. If is a real TTL then when is put to "0" by an output this output must be capable to sink at least 1.6mA from TTL input. In "1" the current involved is more small and not need special care. If is a input buffer TTL compatible(used typicaly in case of CHMOS uC for create TTL compatibility) then the current involved is low and not need special care. In this last case you don't have any problem to use a TTL input buffer as any normal input with CMOS or TTL circuits.

 

[louislu]

Thanks for your replies...according to your reply,for voltage below 0.4V will give us low logic and if greater 2.4V is high-logic right? The chip i m using is MCP2120.here i would like to focus on one of the input pin which is belong to TTL buffer type.i m not goin to use this pin but do i need to connect this pin to Vdd or Vss.if i leave the pin without commection would it affect my chip operation...Thanks in advance....

 

[tavib]

:lol:
Is recommended to put every unused input at Vdd or Vss function by circuit need or function by easy pcb connection.

In case of a real TTL the open inputs is consider in logic "1" state, but the open input is very sensitive to noise and can be easy switch to "0" by this noise.
In case of all CMOS families the open input is in unknown state and can damage the IC if a high supply voltage is used.

So, any unused input must be connected at Vdd or Vss directly or through a resistor, for minimize the hazard.