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WM8816

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PP Rev 1.5 October 2004

11

APPLICATION RECOMMENDATIONS

1.

For best audio performance, all digital activities should be minimised during analogue signal

processing. Special attention should be paid to power and ground decoupling. Decoupling

capacitors should be located as close to the WM8816 as possible. A clean analogue power

supply should always be used.

2.

Damage can be caused to the internal delay generators if AVDD and DVDD supply voltages

differ to any degree. The AVDD and DVDD pins must therefore be tied together in all designs.

3.

During operation of the hardware MUTEB function between setting mute and then un-mute, the

device may either not un-mute or the gain setting after un-mute will be incorrect. It is advised to

re-write the gain settings immediately following hardware un-mute to guarantee faultless

operation.

4.

Voltage greater than 500mV on the digital pins while the device is powered down may prevent

successful POR of the device when power is re-applied. It is preferable that all digital pins are

pulled low during power up or alternatively ensure that there are no residual voltages held on the

digital pins during power down.

5.

The WM8816 output offset voltage can vary dependent upon the op-amp used usually with the

largest level of offset voltage occurring at +15.5dB gain. Output offset voltage has linear

relationship on input bias current and offset voltage amplitudes. Using differing op-amp types

causes a large variation in offset voltage. Below is a list of recommended op-amps which are

found to give the least offset issues when used with the WM8816. Channel matching is also

important factor and not necessarily only the absolute offset value.

DEVICE

MANUFACTURER

OFFSET

IN MV

OP275

Analog Devices

8.55

MC33078/9

On-Semi/ST

28.4

AD8610

Analog Devices

1.49

LT1793

Linear

18.5

OP1177

Analog Devices

0.505

OP277

BurrBrown

0.228

Table 3 Recommended Op-amps

RIN

RMO

WM8816

DAC

Balanced

Output

+

-

RFO

RGND

15

14

13

12

LIN

LMO

+

-

LFO

LGND

2

3

4

5

+18V

+18V

-18V

-18V

+

-

+18V

-18V

2K

2K

2K

2K

Figure 6 Configuration for Double Balanced Output (One Channel)