WM8976 datasheet(80/108 Pages) WOLFSON

80 / 108 page

WM8976

Pre-Production

PP Rev 3.0 April 2006

SYMBOL

MIN

TYPICAL

MAX

UNIT

tline_midrail_on

500

tline_midrail_off

thp_midrail_on

500

thp__midrail_off

tdacint

2/fs

n/fs

DAC Group Delay

29/fs

n/fs

Table 65 Typical POR Operation (typical values, not tested)

Notes:

The lineout charge time, tline_midrail_on, is mainly determined by the VMID pin charge time. This

time is dependent upon the value of VMID decoupling capacitor and VMID pin input resistance

and AVDD power supply rise time. The values above were measured using a 4.7µF capacitor.

It is not advisable to allow DACDAT data input during initialisation of the DAC. If the DAC data

value is not zero at point of initialisation, then this is likely to cause a pop noise on the analogue

outputs. The same is also true if the DACDAT is removed at a non-zero value, and no mute

function has been applied to the signal beforehand.

The lineout discharge time, tline_midrail_off, is dependent upon the value of the lineout coupling

capacitor and the leakage resistance path to ground. The values above were measured using a

10µF output capacitor.

The headphone charge time, thp_midrail_on, is dependent upon the value of VMID decoupling

capacitor and VMID pin input resistance and AVDD power supply rise time. The values above

were measured using a 4.7µF VMID decoupling capacitor.

The headphone discharge time, thp_midrail_off, is dependent upon the value of the headphone

coupling capacitor and the leakage resistance path to ground. The values above were

measured using a 100µF capacitor.

The VMIDSEL and BIASEN bits must be set to enable analogue output midrail voltage and for

normal DAC operation.

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