Type of I/O standard in ASIC

[sivarajm]

Hello,

We know der are many types of I/O standards like
1.LVCOMS
2.LVTTL
3.LVDS
4.SSTL I & II
5.HSTL I & II etc...

Usually what type of I/O will be used in chip, to say more clearly
1. if a chip I/O voltage is 2.5V, what type I/O standard will be preferred and why?
2. This will be decided by whom?

 

[mikersia]

1. I/O type is specified in IC design spec by customer. Type is defined by periphery, that should be connected to this I/O.
For 2.5V supply voltage exist a lot of I/O types, e.g. LVCMOS, LVTTL, ... See correspondent JEDEC standards for clear definition. It should be noted, that IC core and periphery supply voltages could be different, and suitable I/O subset, incorporating level converters, should used.
2. Customer and/or IC designer should define a concrete I/O type.