Product Preview
WM8816
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.
OFFSET
IN MV
DEVICE
MANUFACTURER
OP275
MC33078/9
AD8610
LT1793
Analog Devices
On-Semi/ST
Analog Devices
Linear
8.55
28.4
1.49
18.5
OP1177
OP277
Analog Devices
BurrBrown
0.505
0.228
Table 3 Recommended Op-amps
LFO
3
2
+18V
4
5
LIN
2K
2K
-
LMO
RFO
+
LGND
+18V
DAC
WM8816
-18V
-
Balanced
Output
14
+
+18V
13 RIN
12
2K
-
RMO 15
-18V
+
RGND
-18V
2K
Figure 6 Configuration for Double Balanced Output (One Channel)
PP Rev 1.5 October 2004
11
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
