Production Data

WM8524

w

PD, Rev 4.1, October 2011

21

RECOMMENDED ANALOGUE LOW PASS FILTER

Figure 16 Recommended Analogue Low Pass Filter (one channel shown)

An external single-pole RC filter is recommended if the device is driving a wideband amplifier. Other

filter architectures may provide equally good results.

The filter shown in Figure 16 has a -3dB cut-off at 105.26kHz and a droop of 0.15dB at 20kHz. The

typical output from the WM8524 is 2.1Vrms – when a 10kΩ load is placed at the output of this

recommended filter the amplitude across this load is 1.99Vrms.

RECOMMENDED PCB LAYOUT

C1

C2

C5

To LINEVDD

Supply

To AVDD

Supply

C4

C3

Top Layer Copper

Via

Figure 17 Recommended PCB Layout

Notes:

1.

C5 should be placed as close to WM8524 as possible, with minimal track lengths to reduce inductance and maximise

performance of the charge pump. Vias should be avoided in the tracking to C5.

2.

C1 is then next most important and should also be placed as close as possible to the WM8524. Again, minimise track

lengths and avoid vias to reduce parasitic inductance.

3.

C2 and C4 are then next most important, and lastly C3.

4.

placement and layout to maximise performance with a minimal BOM.