WM7121PE

Rev 4.1

5

ACOUSTIC AND ELECTRICAL CHARACTERISTICS

PARAMETER

SYMBOL

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Directivity

Omni-directional

Polarity

Positive sound pressure

Positive output voltage

Sensitivity

S

94dB SPL

-39

-38

-37

dBV

Acoustic Overload

No Load, THD < 10%

126

dB SPL

Total Harmonic Distortion

THD

100dB SPL

0.1

1

%

114dB SPL

0.2

122dB SPL

1

Signal to Noise Ratio

SNR

A-weighted

65

dB

Dynamic Range

DR

A-weighted

93

dB

Frequency Response

-3dB low frequency

62

Hz

+3dB high frequency

13000

Frequency Response Flatness

200Hz to 6kHz

-1

+1

dB

Acoustic Noise Floor

A-weighted

29

dB SPL

Electrical Noise Floor

A-weighted

-103

dBV

Power Supply Rejection Ratio

PSRR

217Hz sine wave,

100mV (peak-peak)

46

dB

Power Supply Rejection

PSR

217Hz square wave,

100mV (peak-peak)

-72

dBV

Current Consumption

190

240

µA

Output DC Impedance

55

150

Ω

TERMINOLOGY

1.

Sensitivity (dBV)

– Sensitivity is a measure of the microphone output response to the acoustic pressure of a 1kHz 94dB SPL

(1Pa RMS) sine wave.

2.

Total Harmonic Distortion (%)

– THD is the ratio of the RMS sum of the harmonic distortion products in the specified bandwidth

(see note below) relative to the amplitude of the fundamental (ie. test frequency) output.

3.

Signal-to-Noise Ratio (dB)

– SNR is a measure of the difference in level between the output response of a 1kHz 94dB SPL

sine wave and the idle noise output.

4.

Dynamic Range (dB)

– DR is the ratio of the 1% THD microphone output level (in response to a sine wave input) and the idle

noise output level.

5.

All performance measurements are carried out within a 20Hz to 20kHz bandwidth and, where noted, an A-weighted filter.

Failure to use these filters will result in higher THD and lower SNR values than are found in the Acoustic and Electrical

Characteristics. The low pass filter removes out of band noise.