MEASURING NOISE AND SNR
The overall noise of the LMV1088 is measured within the fre-
quency band from 10Hz to 22kHz using an A-weighted filter.
The Mic+ and Mic- inputs of the LMV1088 are shorted for AC
signals via a short between the input capacitors , see Figure
12.
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FIGURE 12. Noise Measurement Setup
For the signal to noise ratio (SNR) the signal level at the out-
put is measured with a 1kHz input signal of 18mV
PP
using an
A-weighted filter. This voltage represents the output voltage
of a typical electret condenser microphone at sound pressure
level of 94dB SPL, which is the standard level for these mea-
surements. The LMV1088 is programmed for 17.5dB of total
gain (20dB pre-amplifier and -2.5dB post-amplifier) with only
Mic1 or Mic2 on. (See also I
2
C Compatible Interface)
The input signal is applied differential between the corre-
sponding Mic+ and Mic- . Because the part is in Pass Through
mode the Low-pass Filter at the output of the LMV1088 is
disabled.
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LMV1088
