WM8940_07 datasheet(10/85 Pages) WOLFSON

10 / 85 page

WM8940

Pre-Production

Pre-Production, Rev 3.0, February 2007

TERMINOLOGY

Full-scale input and output levels scale in relation to AVDD or AVDD2 depending upon the input or output used. For

example, when AVDD = 3.3V, 0dBFS = 1Vrms (0dBV). When AVDD < 3.3V the absolute level of 0dBFS will decrease

with a linear relationship to AVDD.

Input level to RIP and LIP in differential configurations is limited to a maximum of -3dB or performance will be

reduced.

Signal-to-noise ratio (dB) – SNR is the difference in level between a reference full scale output signal and the device

output with no signal applied. This ratio is also called idle channel noise. (No Auto-zero or Automute function is

employed in achieving these results).

Total Harmonic Distortion (dB) – THD is the difference in level between a reference output signal and the first seven

harmonics of that signal. The reference output signal need not be at full scale amplitude; THD is typically measured

using an output power of 20mW into a 16ohm load, corresponding to a reference signal level of -5dB. However the

stated test conditions include input signal level, signal gain settings, output load characteristics and power supply

voltages To calculate the ratio, the fundamental frequency of the output signal is notched out and an RMS value of

the next seven harmonics is calculated.

THD is the difference in level between a reference output signal and the first seven harmonics of the output signal. To

calculate the ratio, the fundamental frequency of the output signal is notched out and an RMS value of the next seven

harmonics is calculated.

Total Harmonic Distortion plus Noise (dB) – THD+N is the difference in level between a reference output signal and

the sum of the harmonics, wide-band noise and interference on the output signal. To calculate the ratio, the

fundamental frequency of the output signal is notched out and an RMS value of the total harmonics, wide-band noise

and interference is calculated.

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

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