RE: [SI-LIST] : Schottky diode termination

Bob Davis (bob@scsi.com)
Fri, 30 Oct 1998 11:40:54 -0800

Rich,

This problem is caused by the storage of the charge in/on the input caused
by the charge from the negative overshoot into the area around the input.
The recovery time is based on the amount of charge injected and the
resistance/capacitance of the area that determines the discharge rate. This
problem will vary from none to severe and from vendor to vendor and is best
avoided through proper termination.

Please also see Jay Shenoy's excellent response.

Bob Davis
Summit Computer Systems, Inc
Signal Integrity Specialists - High Speed, Critical PCB Design
408-353-2706
bob@scsi.com , www.scsi.com

-----Original Message-----
From: owner-si-list@silab.Eng.Sun.COM
[mailto:owner-si-list@silab.Eng.Sun.COM] On Behalf Of Rich.EVANS@st.com
Sent: Thursday, October 29, 1998 5:33 AM
Cc: si-list@silab.Eng.Sun.COM
Subject: RE: [SI-LIST] : Schottky diode termination

Overdriving an IC's input can also cause timing specs
to be violated. I have seen situations where a memory chip's
access time increased significantly when the address inputs were
allowed to overshoot. (I think they were overshooting on H-L, so
they were going below Vss) The memory chips were never damaged,
but apparently they took a while to recover from the "bad"
input signal.

/Rich

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