Answers Database

CPLD: Can the 9500 output buffer drive the load of several 9500s?


Record #3322

Problem Title:
CPLD: Can the 9500 output buffer drive the load of several 9500s?


Problem Description:
KEYWORDS: 9500, CPLD, load, output buffer

URGENCY: Standard

General Description: Can the 9500 output buffer drive the load presented w/3-5 o
ther 9500 outputs (tri-stated) and have an input w/a resistance between 100-200
ohm w/o damaging itself and w/acceptable noise margins?


Solution 1:

The datasheets specify that the output buffers can source 4 mA at Voh = 4.2V and
 can sink 24 mA at Vol = 0.5V.

When the other outputs are tri-stated, you have a
situation of an attached pullup (assume worst case 100 ohms).
When Vol occurs, the pullup will supply (5V-0.5V)/100. This
comes out to roughly 45 mA. It will probably pull up the Voh a
little, but not much.



End of Record #3322