Re: [SI-LIST] : Decoupling:routing

Jay Diepenbrock (jaydiep@us.ibm.com)
Wed, 6 May 1998 09:18:41 -0400

Regarding Tom Zimmerman's posting about the same subject, our experience is
similar for mixed-signal designs. We have found that both noise within the
system and EMI are improved by providing the best possible common Ground for
all subsystems. Problems with digital noise getting into the analog circuitry
were solved by generous use of ferrite beads and decoupling on local power
supply connections, but we had to add local voltage regulators on the analog
power supply lines in some cases because the noise generator (it was an
intentional transmitter) was just so strong that filtering wasn't sufficient to
keep it out. Splitting the Ground plane with common attachment back at the
power supply was the initial approach, but the Ground noise in the analog circui
try with that arrangement was too high.

Jay Diepenbrock

Advisory Engineer
Interconnect Technology & Qualification
IBM Global Procurement, B8UA/061, RTP, NC
Phone: 919-543-8804 Fax: 919-543-3642
Email: jaydiep@us.ibm.com