WM8961
Pre-Production
PCB LAYOUT CONSIDERATIONS
The efficiency of the speaker drivers is affected by the series resistance between the WM8961 and
the speaker (e.g. inductor ESR) as shown in Figure 66. This resistance should be as low as possible
to maximize efficiency.
Figure 66 Speaker Connection Losses
The distance between the WM8961 and the speakers should be kept to a minimum to reduce series
resistance, and also to reduce EMI. Further reductions in EMI can be achieved by additional passive
filtering and/or shielding as shown in Figure 67. When additional passive filtering is used, low ESR
components should be chosen to minimize series resistance between the WM8961 and the speaker,
maximizing efficiency.
LC passive filtering will usually be effective at reducing EMI at frequencies up to around 30MHz. To
reduce emissions at higher frequencies, ferrite beads placed as close to the device as possible will be
more effective.
PP, August 2009, Rev 3.1
109
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
