Production Data

WM8951

w

PD Rev 4.0 May 2005

7

Test Conditions

XTI/MCLK = 256fs unless otherwise stated.

Signal to Noise Ratio

(Note 1,3)

SNR

AVDD1/2= DBVDD=1.8V

DCVDD=1.5V

A-weighted, 0dB gain

80

dB

Dynamic Range (Note 3)

DR

AVDD1/2= DBVDD=1.8V

DCVDD=1.5V

A-weighted, -60dB full

scale input

70

dB

Total Harmonic Distortion

THD

AVDD1/2= DBVDD=1.8V

DCVDD=1.5V

0dB input, 0dB gain

-55

dB

1kHz 100mVpp

50

dB

Power Supply Rejection Ratio

PSRR

20Hz to 20kHz

100mVpp

45

dB

Programmable Gain Boost

MICBOOST bit

set

1kHz input

Rsource < 50 Ohms

34

dB

Mic Path gain (MICBOOST gain

is additional to this nominal

gain)

MICBOOST = 0

Rsource < 50 Ohms

14

dB

Mute attenuation

0dB, 1kHz input

80

dB

Input Resistance

10k

Ω

Input Capacitance

10

pF

Microphone Bias

Bias Voltage

0.75*AVDD1

–100mV

0.75*AVDD1 0.75*AVDD1

+ 100mV

V

Bias Current Source

3

mA

Output Noise Voltage

Vn

1K to 20kHz

25

nV/

√Hz

Notes:

1.

Ratio of output level with 1kHz full scale input, to the output level with the input short circuited, measured ‘A’ weighted over a 20Hz

to 20kHz bandwidth using an Audio analyser.

2.

Ratio of output level with 1kHz full scale input, to the output level with all zeros into the digital input, measured ‘A’ weighted over a

20Hz to 20kHz bandwidth.

3.

All performance measurements done with 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 it is not audible it may affect dynamic specification values.

4.

VMID decoupled with 10uF and 0.1uF capacitors (smaller values may result in reduced performance).

TERMINOLOGY

1.

Signal-to-noise ratio (dB) - SNR is a measure of the difference in level between the full scale output and the output

with no signal applied. (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.