Vega Customer Applications Manual
Section 4 - Output Ripple and Noise
Rev. A3: October 2003
Page 19 of 48
Minimising System noise.
The application note "Vega Connection" gives information on basic connection of Vega and good wiring practice. This
includes using twisted pairs for cabling and de-coupling at loads. This will help minimize noise in a system designed
using Vega power supplies.
There is also an Application note "EMC Installation Notes" in Section 8 which gives more detailed information on
installation to improve EMC performance and reduce system noise.
During system design, if there are any noise problems encountered, there are a number of common causes:
1) No (or insufficient) de-coupling on the PCB and/or at the load.
2) Poor system earthing.
3) Poor routing of the wiring cables.
4) Faulty wiring connection or bad terminations.
5) PCB tracking or cabling insufficient for peak currents carried.
6) Power supply being intermittently overloaded. (High switching currents drawn).
There are a number of practical steps that can be used to help reduce or identify the source of high frequency noise:
1) Try and ascertain if the noise is radiated or conducted by re-orienting the PSU or by screening. If neither helps, the
noise is likely to be conducted noise.
2) Common zero volt connections should be made with the shortest possible wiring either directly or via a capacitor to
the nearest point on the chassis.
3) Ensure the common earth / zero volt connection is connected to the system starpoint earth once only and not by
any other route.
4) Twist all pairs of power and sense cables separately.
5) Try connecting a "ring" of capacitors (100nF ceramics) from rail to rail.
6) Decouple individual rails at the load using capacitors (eg 100nF ceramics).
