buffer required for general input/output signals cpld ?

[h@ro]

Hi all,

recently I fried a CPLD ($12 epm240 board from ebay) trying to drive the Hin/Lin inputs on an ir2101 high/low side mosfet gate driver. I now have a an internal short between a couple of the pins.
I'm assuming the reason for this was drawing too much current from these 2 outputs. Would a series resistor on the outputs help? I don't think the inputs to the ir2101 would require much current though.

I have read that any signals into or out of the CPLD should have internal input/output buffers connected- Though I haven't been doing this in my other designs which have worked in the past. Is this good practice? Also do all inputs and outputs need to be disconnected from the device before re-programming- even if they are kept the same- i.e. all input and output pins are kept the same?

Thoughts on any of the above questions much appreciated!

 

[not-a-moderator]

It is not absolutely necessary to buffer in/outputs from a CPLD to the outside world but it is definitely good practice to do it.
The same is true for series resistors on the outputs. If you switch the outputs too fast while driving a FET gate the gate capacitance and track inductance will surely mess you around and might even damage the CPLD.