WM8952ECSSLASHRV datasheet(53/72 Pages) WOLFSON

53 / 72 page

Pre Production

WM8952

PP, Rev 3.1, June 2011

RECOMMENDED POWER UP/DOWN SEQENCE

In order to minimise output pop and click noise, it is recommended that the WM8952 device is

powered up and down using one of the following sequences:

Power Up:

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

Reset internal registers to default state (software reset).

Enable non-VMID derived bias generator (VMID_OP_EN = 1) and level shifters

(LVLSHIFT_EN = 1).

Select Clock source to MCLK (CLKSEL = 0) and audio mode (Master or Slave).

Enable Power on Bias Control (POB_CTRL = 1) and VMID soft start

(SOFT_START = 1).

Set VMIDSEL[1:0] bits for 50kΩ reference string impedance.

Wait for the VMID supply to settle. *Note 2.

Enable analogue amplifier bias control (BIASEN = 1) and VMID buffer (BUFIOEN

= 1). *Notes 1 and 2.

Disable Power on Bias Control (POB_CTRL = 0) and VMID soft start

(SOFT_START = 0).

Power Down:

Enable non-VMID derived bias generator (VMID_OP_EN = 1).

Enable on Bias Control (POB_CTRL = 1).

Disable analogue amplifier bias control (BIASEN = 0) and VMID (VMIDSEL[1:0]

bits set to OFF).

Enable Fast VMID Discharge (TOGGLE = 1) to discharge VMID capacitor.

Wait for VMID capacitor to fully discharge.

Reset all registers to their default state (software reset).

Turn off external power supply voltages.

Notes:

1. This step enables the internal device bias buffer and the VMID buffer for unassigned inputs. This

will provide a startup reference for all inputs. This will cause the inputs to ramp towards VMID in

a way that is controlled and predictable.

2. Choose the value of VMIDSEL bits based on the startup time (VMIDSEL = 10 for the slowest

startup, VMIDSEL = 11 for the fastest startup). Startup time is defined by the value of the

VMIDSEL bits (the reference impedance) and the external decoupling capacitor on VMID.

In addition to the power on sequence, it is recommended that the zero cross functions are used

when changing the volume in the PGAs to avoid any audible pops and clicks.

WM8952ECS/RV Scheda tecnica(PDF) 53 Page - Wolfson Microelectronics plc