WM5102 datasheet(83/334 Pages) WOLFSON

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Production Data

WM5102

PD, June 2014, Rev 4.2

LOW PASS / HIGH PASS DIGITAL FILTER (LHPF)

The digital core provides four Low Pass Filter (LPF) / High Pass Filter (HPF) processing blocks as

illustrated in Figure 32. A 4-input mixer is associated with each filter. The 4 input sources are

selectable in each case, and independent volume control is provided for each path. Each Low/High

Pass Filter (LHPF) block supports 1 output.

The Low Pass Filter / High Pass Filter can be used to remove unwanted ‘out of band’ noise from a

signal path. Each filter can be configured either as a Low Pass filter or High Pass filter.

Figure 32 Digital Core LPF/HPF Blocks

The LHPF1, LHPF2, LHPF3 and LHPF4 mixer control registers (see Figure 32) are located at register

addresses R2304 (900h) through to R2335 (91Fh).

The full list of digital mixer control registers is provided in the “Register Map” section (Register R1600

through to R2920). Generic register definitions are provided in Table 7.

The *_SRCn registers select the input source(s) for the respective LHPF processing blocks. Note that

the selected input source(s) must be configured for the same sample rate as the LHPF to which they

are connected. Sample rate conversion functions are available to support flexible interconnectivity -

see “Asynchronous Sample Rate Converter (ASRC)” and “Isochronous Sample Rate Converter

(ISRC)”.

The bracketed numbers in Figure 32, eg. “(60h)” indicate the corresponding *_SRCn register setting

for selection of that signal as an input to another digital core function.

The sample rate for the LHPF function is configured using the FX_RATE register - see Table 21. Note

that the EQ, DRC and LHPF functions must all be configured for the same sample rate.

The LHPF function supports audio sample rates in the range 8kHz to 192kHz. When the DRC is

enabled, the maximum sample rate for the EQ, DRC and LHPF functions is 96kHz.

Sample rate conversion is required when routing the LHPF signal paths to any signal chain that is

asynchronous and/or configured for a different sample rate.

The control registers associated with the LHPF functions are described in Table 15.

The cut-off frequencies for the LHPF blocks are set using the coefficients held in registers R3777,

R3781, R3785 and R3789 for LHPF1, LHPF2, LHPF3 and LHPF4 respectively. These coefficients are

derived using tools provided in Wolfson’s WISCE™ evaluation board control software; please contact

your local Wolfson representative for more details.

WM5102 Datasheet(PDF) 83 Page - Wolfson Microelectronics plc