Schottky Diode terminator SIP packages

Howard W. Johnson (howiej@olympic-tech.com)
Sat, 8 Jun 1996 13:41:55 -0700 (PDT)

Just a quick idea here. To avoid cross-coupling
effects between the lines of your bus, the schottky
diodes may likely have to be packaged in a SIP that
has separate VCC/GND connections for each diode
(see quantitative details of a the use of SIPS for
resistive terminations on p. 247 of High-Speed
Digital Design, Prentice-Hall, 1993). If the SIP
is wired to let the diodes share common VCC and
GND pins, the effective inductance in series with each
diode will be too great. You aren't likely to meet your
1.5 nS switching time requirement.

Of course, the problem with individual VCC/GND pins for
each diode is that you will need 3 pins per terminated
bus line. That's not very good density, and you
indicated that you had little room to spare.

Here's a thought: you could try using the protection
diodes already built into some other existing part to solve
your problem. Try using a multiple-input
device (like a multiplexor) that has multiple
VCC and GND pins, or is packaged in a much smaller
package than a SIP, and has good protection diodes.
Just connect it in parallel with your bad receiver.
A multiplexor part has a lot of inputs and wastes only
one pin as an output.

>Errors-To: si-admin@silab.Eng.Sun.COM
>Errors-To: si-admin@silab.Eng.Sun.COM
>Date: Fri, 7 Jun 96 13:44 PDT
>From: scottmc@icx.com (Scott McMorrow)
>To: si-list@silab.Eng.Sun.COM
>Subject: Schottky Diode terminator SIP packages
>
>Hello all,
>
>I'm looking for schottky diode terminators to solve
>a signal integrity problem on a current system add-in
>board. Because of space requirements, the terminators
>need to be in a sip package.
>
>Is anyone aware of, or had experiences with, sip diode
>terminators that are currently available from any
>vendor. These diodes need to have a low input
>capacitance < 3pF and fast turn-on time < 1.5 ns
>to compensate for poor CMOS ESD protection diodes in
>an existing device.
>
>Any help someone can provide will be appreciated.
>
>regards,
>
>--scott
>
>
_________________________________________________
Howard W. Johnson, Olympic Technology Group, Inc.
U.S. tel (206) 556 0800 // fax 206 881 1491 // email howiej@olympic-tech.com