IO pins : short circuit protection ?

Timo,

If you look in the IBIS models (there are in ASCII), you will find the protection diode IV curves.

As long as you stay within the Absoulte Maximum (Table 1, section 3) limits of the specifications for any currents and voltages, everything will be just fine.

Shorting an IO pin to ground momentarily will not damage the device. Shorting it for months just might damage it.

Shorting more than one pin to ground momentarily will also not damage the device.

Shorting ten or more to ground for a long time just might damage the device.

Driving an output pin with another chip is likely to damage the other chip, not the FPGA.

Aust> Hello

I read the ibis modell for my fpga

Ok, but that doesn't mean any short circuit protection, as 180mOhm isn't that much...

I'm not sure if I understand this : When connecting a 5V voltage source to the fpga-io-pin (as pulldown-output), a current of 0.25A would be fed ?

This is a thing that I can't find in the file spartan2.ibs...

And that is a thing that I want to prevent. So I thought putting a resistor between an A/D-converter and falsely output-switched io-pin to prevent a hughe current. What I simply wanted to ask is, how much current is acceptable ?

Regards, Timo

Timo,

Page 1, Table 1. Look at the allowed voltage. Then use the diode IV table in the IBIS model to find current.

From the file, [POWER_clamp] | voltage I(typ) I(min) I(max) | -3.30 6.17A 6.28A 6.12A -3.20 5.90A 6.01A 5.86A -3.10 5.64A 5.75A 5.60A -3.00 5.38A 5.49A 5.33A -2.90 5.11A 5.23A 5.07A -2.80 4.85A 4.96A 4.80A -2.70 4.59A 4.70A 4.54A -2.60 4.32A 4.44A 4.28A -2.50 4.06A 4.18A 4.01A -2.40 3.80A 3.91A 3.75A -2.30 3.54A 3.65A 3.49A -2.20 3.27A 3.39A 3.23A -2.10 3.01A 3.13A 2.97A -2.00 2.75A 2.87A 2.71A -1.90 2.49A 2.61A 2.44A -1.80 2.23A 2.35A 2.18A -1.70 1.97A 2.10A 1.93A -1.60 1.72A 1.84A 1.67A -1.50 1.46A 1.59A 1.41A -1.40 1.21A 1.33A 1.16A -1.30 0.96A 1.08A 0.91A -1.20 0.71A 0.84A 0.66A -1.10 0.47A 0.60A 0.42A -1.00 0.25A 0.38A 0.21A -0.90 78.20mA 0.18A 53.88mA -0.80 14.96mA 44.93mA 18.61mA -0.70 6.69mA 8.78mA 10.98mA -0.60 2.80mA 2.96mA 5.51mA -0.50 0.68mA 0.83mA 1.82mA -0.40 81.59uA 0.14mA 0.29mA -0.30 5.30uA 14.08uA 20.76uA -0.20 0.23uA 1.07uA 0.81uA -0.10 8.35nA 67.32nA 24.93nA 0.00 1.14nA 6.95nA 4.38nA

So, if -0.5 V is the abs max, then the anything less than 1.82 mA is perfectly safe.

Generally speaking, less than 10 mA will not affect operation, and will not hurt anything. Anything more than that, will probably affect functionality. Damage will occur above ~ 100 mA.

Austin

Timo Dammes wrote:

Thank you