WAN-0129

www.DataSheet4U.com w INTRODUCTION WAN-0129 Decoupling and Layout Methodology for Wolfson DACs, ADCs and CODECs This application note looks at the general decoupling and layout practice required for Wolfson converters to achieve maximum performance in a typical high-speed mixed-signal circuit. APPLICATION Wolfson DACs, ADCs and CODECs have both digital and analogue interfaces. It is important that noise is minimised to get the maximum converter performance. In our datasheets there are a number of supply pins on each chip. They are labelled according to their internal connection, not necessarily how they should be connected externally. The datasheets show typical supply connections and decoupling arrangements and this report goes into further details. GROUNDING First consider the grounding of the IC. Ideally the circuit board will have a single continuous ground plane, with all ground pins connected to it. The components will be located so that high-speed digital devices are kept away from analogue devices, so that noise currents do not stray where they are not wanted. In some cases a cut between analogue and digital planes is required, because the component positions cannot be optimised. In this case the analogue and digital grounds must be connected under the converter with a wide copper track. Just using a zero-ohm link may not provide a good enough connection in some circumstances. Ensure any tracks going from the board’s analogue section to the digital section (e.g....