[SI-LIST] Re: Crowbar current in push-pull drivers
- From: Robert Kezer <Robert.Kezer@xxxxxxxxxxxxx>
- To: "'fasig.jonathan@xxxxxxxx'" <fasig.jonathan@xxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Fri, 29 Aug 2003 12:01:25 -0400
It depends on who designed the driver. I have seen designs that
bootstrap the input to the output transistors and it creates this high
crowbar current you are seeing. It is kind of like adding pre-emphasis
in a crude way.
I have also seen designs that do not
do this and the crowbar current is less, but still greater than
8mA for an HSTL Class I device.
Depends on the bandwidth you want out of the buffer and the media
you are going to drive. Since we are driving nothing more than
a circuit board, we have opted for a slower, less robust design.
Jonathan, tell Barry Gilbert and Dan Schwabb I said hi.
Regrads,
Bob Kezer
-----Original Message-----
From: Fasig, Jonathan L. [mailto:fasig.jonathan@xxxxxxxx]
Sent: Friday, August 29, 2003 11:51 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Crowbar current in push-pull drivers
Does anybody have a feel for how much crowbar current
(aka shoot-thru current) one should expect to see from a
"well-behaved" HSTL-Class-1 or SSTL-18 driver? I am seeing
43ma and 23ma transients (respectively, per driver) on the
I/O supply when my drivers are switching. These transients
are two hundred to three hundred picoseconds in duration.
Are these switching transients typical?
---------------------------------------------------------------
Jonathan Fasig Email: fasig.jonathan@xxxxxxxx
Mayo Foundation
4001 41st Street NW
MSC Sn 2-132 Phone: (507) 538-5464
Rochester, MN 55901 Fax: (507) 284-9171
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