[SI-LIST] : Is a magnetic field influenced by trace width?

About this list Date view Thread view Subject view Author view

From: Patrick Lawler ([email protected])
Date: Thu May 03 2001 - 14:53:18 PDT


I have a question concerning the magnetic field generated by
switching currents in a pair of PWB traces.

The situation arises when our PWB designers make traces in our
switch-mode power supply extra wide. I'm concerned that the extra
trace area is generating a larger magnetic field, helping to
couple pulse currents into other parts of the circuit, causing
EMI problems.

Given conditions:
1) A trace pair is on one layer of a PWB.
2) A trace pair carries both outgoing and return currents.
3) The traces carry only DC voltage - there are no switching
voltages.
4) The currents are typical of switch-mode power supplies: a
100kHz fundamental of 0-6Apk, with rise & fall times of 100ns.
5) The air gap between the two traces in each configuration is
the same - only the trace width is different.

Will Configuration 1 generate a larger magnetic field than
Configuration 2?

Configuration 1:
----------------------------
copper copper copper copper
copper copper copper copper
copper copper copper copper
----------------------------
          gap
----------------------------
copper copper copper copper
copper copper copper copper
copper copper copper copper
----------------------------

Configuration 2:
----------------------------
copper copper copper copper
----------------------------
          gap
----------------------------
copper copper copper copper
----------------------------

**** To unsubscribe from si-list or si-list-digest: send e-mail to
[email protected]. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Jun 21 2001 - 10:11:50 PDT