WM8978 Wolfson Microelectronics Ltd., WM8978 Datasheet - Page 24

• Manufacturer Part Number: WM8978
• Description: The WM8978 is a low power, high quality stereo codec designed for portable applications such as Digital still camera or Digital Camcorde
• Manufacturer: Wolfson Microelectronics Ltd.

WM8978
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Table 5 Typical POR Operation (typical values, not tested)
1.
2.
3.
4.
5.
6.
DAC Group Delay
Notes:
t
t
t
t
hp__midrail_off
line_midrail_on
line_midrail_off
hp_midrail_on
SYMBOL
The lineout charge time, t
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, t
capacitor and the leakage resistance path to ground. The values above were measured using a
10µF output capacitor.
The headphone charge time, t
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, t
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.
t
dacint
MIN
TYPICAL
29/fs
line_midrail_on,
500
500
2/fs
1
6
line_midrail_off,
hp_midrail_on,
hp_midrail_off,
MAX
is mainly determined by the VMID pin charge time. This
is dependent upon the value of the lineout coupling
is dependent upon the value of VMID decoupling
is dependent upon the value of the headphone
UNIT
n/fs
n/fs
ms
ms
s
s
PTD Rev 2.6 November 2005
Preliminary Technical Data
24