Production Data
WM8781
Test Conditions
DVDD = 3.3V, AVDD = 5.0V, TA = +25oC, 1kHz signal, A-weighted, fs = 48kHz, MCLK = 256fs, 24-bit audio data, Slave Mode
unless otherwise stated.
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Analogue Reference Levels
Midrail Reference Voltage
VMID
AVDD to VMID and
VMID to VREFN
–3%
AVDD/2
+3%
V
Potential Divider Resistance
Buffered Reference Voltage
VREF source current
VREF sink current
RVMID
VREFP
IVREF
50
kΩ
V
–3%
AVDD/2
+3%
5
5
mA
mA
IVREF
Supply Current
Analogue supply current
Digital supply current
Power Down
AVDD = 5V
32
5
mA
mA
mA
DVDD = 3.3V
0.5
Notes:
1. All performance measurements are done with a 20kHz low pass filter, and where noted an A-weight filter. Failure to
use such a filter will result in higher THD+N and lower SNR and Dynamic Range readings than are found in the
Electrical Characteristics. The low pass filter removes out of band noise; although this is not audible, it may affect
dynamic specification values.
2. VMID is decoupled with 10uF and 0.1uF capacitors close to the device package. Smaller capacitors may reduce
performance.
3. This high leakage current is due to the topology of the instate pads. The pad input is connected to the midpoint of an
internal resistor string to pull input to vmid if undriven.
TERMINOLOGY
1. Signal-to-noise ratio (dB) – Ratio of output level with 1kHz full scale input, to the output level with all zeros into the
digital input, over a 20Hz to 20kHz bandwidth. (No Auto-zero or Automute function is employed in achieving these
results).
2. Dynamic range (dB) – DR is a measure of the difference between the highest and lowest portions of a signal.
Normally a THD+N measurement at 60dB below full scale. The measured signal is then corrected by adding the 60dB
to it. (e.g. THD+N @ -60dB= -32dB, DR= 92dB).
3. THD+N (dB) – THD+N is a ratio, of the rms values, of (Noise + Distortion)/Signal.
4. Channel Separation (dB) – Also known as Cross-Talk. This is a measure of the amount one channel is isolated from
the other. Normally measured by sending a full scale signal down one channel and measuring the other.
PD, April 2006, Rev 4.1
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
