[SI-LIST] Interface standards
- From: Canes Venatici <starsilic@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 16 Jan 2007 03:28:28 -0800 (PST)
Hi,
I've a fundamental doubt of whether the i/o drivers (pads) are designed
considering the interface it supports?
Why I'm asking is if suppose a driver operates at an i/o supply of 2.5/3.3v,
with the options of pad supporting
LVTTL(3.3V) or SSTL (2/1.8) interfaces. Actually the driver gives output (no
load) switching between 2.5v/3.3v and 0v,
independent of interfacing standard.
For LVTTL, the driver can directly operate on loads (no series/pullup resistors
at the interface, between pad and load, is mandatory).
For SSTL2 (class-I), by providing, at the output pad, a) series resistor
(25ohms) , b) assuming a transmission line (PCB modelling) of
Z0=50, and c) having a pullup of ref. voltage thro' 50ohms, the interface
becomes SSTL.
I mean the driver design, need not be concerned with the type of interface. Its
basically the type of interface, differentiates it to SSTL/LVTTL.
Probably, in the receiver side the comparator design (diff
amplifier/comparator) differentiates SSTL/LVTTL.
Could anyone comment on my statements....
Regards,
Canes
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