What is the output of PADs resistor?

[kinysh]

pad output resistance

when using a PAD, the lib usually give you driving strength.
such as 12mA.

but in the high speed design, the calculation always use driving resistor.

does anyone konws the output pad's resistor?
that should have something to do with the driving strength.

Bests
kinysh

 

[sandusty]

pad output resistance

If there is a resistance value on the output pad, how can you put down the resistances behind it? Wiring from pad to lead fram, pin/ball soldering, resistance on the board... not to mention about the capacitance

With the pad resistance, you still can do nothing

V = IR, if you know the pad supplied voltage and driving strength.... what do you guess next???
8)

 

[sunjimmy]

pad output resistance

As far as i know, the output pad impedance should match the impedance outside the chip to prevent signal reflection during high speed design. But usually the driving strength of IO pad (~12mA) is measured when VOL=0.4v or VOH=2.4v under DC condition. If you want to know the impedance of PMOS/NMOS inside IO pad, you must take a look at the IO pad layout to figure out the device dimension, then do some spice simulation to see what impedance it is.