At 10:24 AM 3/5/98 -0700, D. C. Sessions wrote:
>Mark Nass wrote:
>> Can someone explain to me what driver strength means?
>That's a good question with no good answer.
>> a driver is spec'd by an ASIC vendor as a 12ma, 6ma, etc what does
>> that mean
>Pretty much whatever the vendor wants it to. In some cases the
>number is more-or-less worst case, sometimes typical, sometimes
>at useful voltages, sometimes not. At VLSI in our 350nm library
>the Iol is measured at near-worst-case and 350mv, while the
>Ioh is measured at 2450mv. Notice that the pullups are weaker
>than then pulldowns. In our 200nm libraries the numbers are at
>350mv from the rail for both pullup and pulldown.
>> as far as its expected VI curve
>Anybody's guess. Process variables, predriver supplies,
>possibly architecture, all influence the shape of the V/I
>curve. About all you can count on is the slope near the rail.
>> and how many loads
>> I can expect it to drive?
>Welcome to the world of signal integrity. You aren't driving
>the loads, you're driving the wires. If you're willing to wait
>long enough there's almost no limit on the number of loads even
>a weak driver can manage.
>D. C. Sessions