WM8978 Wolfson Microelectronics Ltd., WM8978 Datasheet - Page 21
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WM8978
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.
Datasheet
1.WM8978.pdf
(108 pages)
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Preliminary Technical Data
RECOMMENDED POWER UP/DOWN SEQUENCE
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In order to minimise output pop and click noise, it is recommended that the WM8978 device is
powered up and down using one of the following sequences:
Power-up when NOT using the output 1.5x boost stage:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Power-up when using the output 1.5x boost stage:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10. Enable other mixers as required.
11. Enable other outputs as required.
12. Set remaining registers.
Power Down (all cases):
1.
2.
3.
4.
5.
Turn on external power supplies. Wait for supply voltage to settle.
Mute all analogue outputs.
Set L/RMIXEN = 1 and DACENL/R = 1 in register R3.
Set BUFIOEN = 1 and VMIDSEL[1:0] to required value in register R1. Wait for the VMID supply
to settle. *Refer notes 1 and 2.
Set BIASEN = 1 in register R1.
Enable other mixers as required.
Enable other outputs as required.
Set remaining registers.
Turn on external power supplies. Wait for supply voltage to settle.
Mute all analogue outputs.
Enable unused output chosen from L/ROUT2, OUT3 or OUT4. If unused output not available,
chose one of these outputs not required at power up.
Set BUFDCOPEN = 1 and BUFIOEN = 1 in register R1.
Set SPKBOOST = 1 in register R49.
Set VMIDSEL[1:0] to required value in register R1. Wait for the VMID supply to settle. *Refer
notes 1 and 2.
Set L/RMIXEN = 1 and DACENL/R = 1 in register R3.
Set BIASEN = 1 in register R1.
Set L/ROUT2EN = 1 in register R3. *Note 3.
Mute all analogue outputs.
Disable Power Management Register 1. R1 = 0x00.
Disable Power Management Register 2. R2 = 0x00.
Disable Power Management Register 3. R3 = 0x00.
Remove external power supplies.
Set L/ROUT1EN = 1 in register R2.
PTD Rev 2.6 November 2005
WM8978
21