EVAL-ADMP441Z AD [Analog Devices], EVAL-ADMP441Z Datasheet - Page 10

• Manufacturer Part Number: EVAL-ADMP441Z
• Description: Omnidirectional Microphone
• Manufacturer: AD [Analog Devices]

ADMP441
DIGITAL FILTER CHARACTERISTICS
The
high-pass filter eliminates unwanted low frequency signals.
A low-pass filter allows the user to scale the pass band with
the sampling frequency as well as perform required noise
reduction.
High Pass Filter
The
dc and very low frequency components. Table 7 shows the high-
pass characteristics for a nominal sampling rate of 48 kHz. The
cutoff frequency scales with changes in sampling rate.
Table 7. High-Pass Filter Characteristics
Frequency
3.7 Hz
10.4 Hz
21.6 Hz
This digital filter response is in addition to the natural high-
pass response of the
has a −3 dB cutoff of 60 Hz.
Low-Pass Filter
The analog-to-digital converter in the
high order, sigma-delta (Σ-Δ) running at a high oversampling
ratio. The noise shaping of the converter pushes the majority of
the noise well above the audio band and gives the microphone a
ADMP441
ADMP441
incorporates a high-pass filter to remove unwanted
has an internal digital band-pass filter. A
ADMP441
Attenuation
–3.0 dB
–0.5 dB
–0.1 dB
MEMS acoustic transducer that
ADMP441
is a single-bit,
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wide dynamic range. However, it does require a good quality
low-pass filter to eliminate the high frequency noise.
Figure 13 shows the response of this digital low-pass filter
included in the microphone. The pass band of the filter extends
to 0.423 × f
ripple. The high frequency cutoff of −6 dB occurs at 0.5 × f
48 kHz sampling rate results in a pass band of 20.3 kHz and a
half amplitude corner at 24 kHz; the stop-band attenuation of
the filter is greater than 60 dB. Note that these filter specifica-
tions scale with sampling frequency.
–100
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
0
Figure 13. Digital Low-Pass Filter Magnitude Response
S
and, in that band, has an unnoticeable 0.04 dB of
0.1
0.2
NORMALIZED FREQUENCY (
0.3
0.4
0.5
0.6
0.7
f
S
)
Data Sheet
0.8
0.9
1.0
S
. A