Preliminary Technical Data
WM7220
ACOUSTIC AND ELECTRICAL CHARACTERISTICS
Test Conditions: VDD=1.8V, 1kHz test signal, CLK=2.4MHz, TA = 25°C
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Directivity
Omni-directional
Sensitivity (WM7220)
Sensitivity (WM7220E)
Acoustic Overload
Signal to Noise Ratio
Total Harmonic Distortion
Frequency Response
S
S
94 dB SPL
94 dB SPL
-29
-27
-26
-26
120
58
-23
-25
dBFS
dBFS
dB SPL
dB
THD < 10%
SNR
THD
A-Weighted
100dB SPL
0.1
35
1
%
-3dB Low frequency
+3dB High frequency
A-weighted
Hz
9000
36
Hz
Acoustic Noise Floor
Electrical Noise Floor
Power Supply Rejection
dB SPL
dBFS
dBFS
A-weighted
-84
-65
PSR
217Hz Square Wave
100mV pk-pk
Digital Input / Output
CLK Input HIGH Level
VIH
VIL
0.65 x
VDD
V
V
V
V
CLK Input LOW Level
DAT Output HIGH Level
DAT Output LOW Level
Input capacitance (CLK)
0.35 x
VDD
VOH
VOL
IOH = +1mA
IOL = -1mA
0.9 x
VDD
0.1 x
VDD
CIN
0.5
pF
pF
Maximum load capacitance
(DAT)
CLOAD
100
Input Leakage
1
μA
Short Circuit Output Current
Miscellaneous
ISC
DAT connected to GND
10
mA
Current Consumption
IVDD
Active Mode
SLEEP Mode
From OFF
650
2
μA
ms
10
Start-up Time
10
10
From SLEEP
CLK Sleep Frequency
1.0
kHz
TERMINOLOGY
1. Sensitivity (dBFS) - Sensitivity is a measure of the microphone output response to the acoustic pressure of a 1kHz
94dB SPL (1Pa RMS) sine wave. This is referenced to the output Full Scale Range (FSR) of the microphone.
2. Full Scale Range (FSR) - Sensitivity, Electrical Noise Floor and Power Supply Rejection are measured with reference
to the output Full Scale Range (FSR) of the microphone. FSR is defined as the amplitude of a 1kHz sine wave output
whose positive peak value reaches 100% density of logic 1s and whose negative peak value reaches 0% density of
logic 1s. This is the largest undistorted 1kHz sine wave that will fit in the digital output numerical range. Note that,
because the definition of FSR is based on a sine wave, it is possible to support a square wave test signal output
whose level is +3dBFS.
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. 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 RMS amplitude of the fundamental (ie. test frequency) output.
5. All performance measurements are carried out with 20kHz 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 brick wall filter removes out of band noise.
PTD, Rev 2.3, December 2011
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
