> ... but the customer is very specific about having LVTTL logic 
> thresholds.

I wondered, "Why?"

Which was answered by -

> but customer is insistant on meeting the actual LVTTL levels after 
> problems with another vendors part.

I don't know how savvy the customer is, but it sounds like they are 
falling into the all too common trap of telling you how they want 
something done, rather than specifying what they actually require. In 
this case I suspect that specs of 0.6V or 0.8V are by themselves 
likely to be reasonably meaningless. One would need to ensure these 
were worst case, were over temperature and supply voltage and phase of 
the moon, and more. One man's / supplier's looser apparent spec may be 
a better one if it is actually adhered to and a notionally better one 
isn't.

Anyone system which has problems with levels of eg 0.6V versus 0.8V is 
probably sailing too close to the wind for comfort in any case. When 
reality strikes the system is in risk of doing so too.

I'd suggest that you ask the customer to let you *engineer* / *design* 
the system so that it is guaranteed to work, using whatever parts you 
deem will do the job. What a novel idea :-). The alternative is to 
risk giving them what they ask for but failing to deliver what they 
want. Design may be difficult if the existing system is poorly enough 
specd to not work with all brands of reasonably compatible ICs, but 
finding out what it's limitations are and designing for them is 
superior to follow a recipe book.



        RM


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