Protection diodes

Created Wed, 27 Jul 2011 11:02:00 +0000 by svofski

svofski

Wed, 27 Jul 2011 11:02:00 +0000

Is there a part number, reference, datasheet on the protection diodes used on I/O lines, D3 etc? I'm particularly interested in their junction capacitance. I suspect that they, together with 200ohm resistors, make a great lowpass filter.

svofski

Wed, 27 Jul 2011 12:16:42 +0000

Actually, nevermind. I estimate the max diode capacitance together with pin capacitance to be about 20pF, 30pF if things are really really bad (they are, long wires and stuff) and with 200ohm resistor that makes Fc to be about 26MHz. And I'm having a problem with 12MHz pulses.

The real issue seems to be with the builtin comparator, which has a typical response time of 150ns, worst case 400ns. 12MHz == 83ns pulses, the retarded comparator just can't notice as they pass through. Feh Microchip, you never cease to disappoint.

GeneApperson

Wed, 27 Jul 2011 16:21:52 +0000

In case you're still interested:

The clamp diodes are BAV99W-7 from Diodes Inc. The ESD zener diodes are NSQA6V8AW5T2 from On Semiconductor.

Gene Apperson Digilent

KM6VV

Wed, 27 Jul 2011 18:24:21 +0000

I am!

Thanks!

Alan KM6VV

svofski

Thu, 28 Jul 2011 10:57:08 +0000

In case you're still interested: The clamp diodes are BAV99W-7 from Diodes Inc. The ESD zener diodes are NSQA6V8AW5T2 from On Semiconductor.

Yes, I am. Thank you! I will remember these for future reference.