Preliminary Technical Data
WM7121
ACOUSTIC AND ELECTRICAL CHARACTERISTICS
Test Conditions: VDD=2.1V, 1kHz test signal, TA = 25°C
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Directivity
Omni-directional
Sensitivity (WM7121)
Sensitivity (WM7121E)
Acoustic Overload
S
S
94dB SPL
94dB SPL
-41
-39
-38
-38
126
-35
-37
dBV
dBV
No Load
dB SPL
THD < 10%
Signal to Noise Ratio
Total Harmonic Distortion
Dynamic Range
SNR
THD
DR
A-Weighted
65
0.25
91
dB
%
104dB SPL
A-Weighted,
dB
Noise floor to 1% THD
-3dB Low Frequency
+3dB High Frequency
A-Weighted
Frequency Response
62
15000
29
Hz
Hz
Acoustic Noise Floor
dB SPL
dBV
dB
Electrical Noise Floor
Power Supply Rejection Ratio
Current Consumption
Output DC Impedance
A-Weighted
-103
53
PSRR
IVDD
100mV RMS, 217Hz
200
100
µA
ZOUT
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. 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.
3. Total Harmonic Distortion (dB) – 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.
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 with 20 kHz low pass ‘brick wall’ filter 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.
PTD, Rev 2.0, October 2012
w
5
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
