WM8753LGEBSLASHV datasheet(89/92 Pages) WOLFSON

89 / 92 page

WM8753L

Pre-Production

PP Rev 3.4 November 2005

MINIMISING POP NOISE AT THE ANALOGUE OUTPUTS

To minimise any pop or click noise when the system is powered up or down, the following procedures

are recommended.

POWER SUPPLIES

The ideal way to apply power to the WM8753 is to all supplies at the same time.

This is not always possible in many designs due to supplies being sourced from different voltage

regulators or direct from batteries. In these situations, it is recommended that supplies are applied in

the following order.

1. DCVDD, DBVDD and PVDD (if not at the same time, any order may be used)

2. AVDD

3. HPVDD and SPKRVDD (if not at the same time, any order may be used)

Supplies may be removed in any order. However, it is recommended that HPVDD and SPKRVDD

supplies be removed last.

POWER UP

Switch on power supplies. By default the WM8753L is in Standby Mode, the DAC is

digitally muted and the Audio Interface and Outputs are all OFF

Enable Vmid and VREF. Allow VREF to settle. The settling time depends on the

value of the capacitor connected at VMID, and the size of the resistors selected

using VMIDSEL (

τ = RC).

Enable DACs, etc. as required.

Enable outputs as required.

Set DACMU = 0 to un-mute the audio DACs.

POWER DOWN (MINIMUM NOISE)

Set DACMU = 1 to mute the audio DACs.

Disable all Outputs.

Disable VREF and VMIDSEL.

Switch off the power supplies

POWER DOWN (QUICKEST MIDRAIL DISCHARGE)

Set DACMU = 1 to mute the audio DACs.

Disable VREF and VMIDSEL.

Switch off the power supplies.

A choice of two power down sequences have been recommended. The first is completely noise free

with the disadvantage that the mid-rail voltage can take some time to discharge due to the large

amount of capacitance attached to the outputs. The second offers a quick discharge of the output

capacitors but as the outputs have not been powered down it does allow for the small possibility that

noise may be heard during power down.

WM8753LGEB/V Datasheet(PDF) 89 Page - Wolfson Microelectronics plc