Datasheet

10
1k
1M
FREQUENCY (Hz)
-5
5
20
GAIN (dB)
100k
10k
100
15
10
0
V
DD
= 2.2V
-40°C
25°C
85°C
ABSOLUTE
SOUND
PRESSURE
[dBPa]
-94 dB
SENSITIVITY
[dBV/Pa]
SOUND
PRESSURE
[dB SPL]
VOLTAGE
[dBV]
LMV1012
SNAS194H –NOVEMBER 2002–REVISED MAY 2013 www.ti.com
Figure 24. dB SPL to dBV Conversion
Example: Busy traffic is 70 dB SPL
V
OUT
= 70 −94 −44 = −68 dBV (4)
This is equivalent to 1.13 mV
PP
Since the LMV1012-15 has a gain of 6 (15.6 dB) over the JFET, the output voltage of the microphone is 6.78
mV
PP
. By implementing the LMV1012-15, the sensitivity of the microphone is -28.4 dBV/Pa (−44 + 15.6).
LOW FREQUENCY CUT OFF FILTER
To reduce noise on the output of the microphone a low frequency cut off filter has been implemented. This filter
reduces the effect of wind and handling noise.
It's also helpful to reduce the proximity effect in directional microphones. This effect occurs when the sound
source is very close to the microphone. The lower frequencies are amplified which gives a bass sound. This
amplification can cause an overload, which results in a distortion of the signal.
Figure 25. LMV1012-15 Gain vs. Frequency Over Temperature
The LMV1012 is optimized to be used in audio band applications. By using the LMV1012, the gain response is
flat within the audio band and has linearity and temperature stability (see Figure 25).
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