WM8985GEFLSLASHR datasheet(23/121 Pages) WOLFSON

23 / 121 page

Production Data

WM8985

PD, Rev 4.6, July 2009

RECOMMENDED POWER UP/DOWN SEQUENCE

In order to minimise output pop and click noise, it is recommended that the WM8985 device is

powered up and down under control using the following sequences:

Power Up:

Turn on external power supplies. Wait for supply voltage to settle.

Set low analogue bias mode, BIASCUT = 1

Enable thermal shutdown TSDEN = TSOPCTRL = 1

Enable Internal bias BIASEN = 1.

Mute all outputs and set PGAs to minimum gain, R52 to R57 = 0x140h.

Enable VMID independent current bias, POBCTRL = 1.

Enable required outputs, DACs and mixers.

Enable VMID with required charge time e.g. VMIDSEL=01.

Wait 500ms 1

10. Setup digital interface, input amplifiers, PLL, ADCs and DACs for desired operation.

11. Disable VMID independent current bias, POBCTRL = 0.

12. Unmute L/ROUT1 and set desired volume, e.g. for 0dB R52 and R53 = 0x139h.

13. Unmute L/ROUT2 and set desired volume, e.g. for 0dB R54 and R55 = 0x139h.

Power Down 2:

Disable Thermal shutdown, TSDEN = TSOPCTRL = 0

Disable VMIDSEL=00 and BIASEN=0

Wait for VMID to discharge 3

Power off registers R1, R2, R3 = 0x000h

Remove external power supplies

Notes:

Charging time constant is determined by impedance selected by VMIDSEL and the value of

decoupling capacitor connected to VMID pin.

It is possible to interrupt the power down sequence and power up to VMID before the allocated

VMID discharge time. This is done by following the power-up sequence omitting steps 4 to 8.

Discharge time constant is determined by the values of analogue output capacitors.

WM8985GEFL/R データシート(PDF) 23 Page - Wolfson Microelectronics plc