Datasheet

SSM2166
Rev. D | Page 14 of 20
00357-026
IC2
IC1
Figure 27. Evaluation Board Topside Silkscreen (Not to Scale)
0
0357-027
Figure 28. Evaluation Board Topside Metallization (Not to Scale)
00357-028
Figure 29. Evaluation Board Backside Metallization (Not to Scale)
EVALUATION BOARD EXAMPLES
To illustrate how easy it is to program the SSM2166, a practical
example is provided. The SSM2166 was used to interface an
electret-type microphone to a postamplifier. The evaluation
board or the circuit configuration shown in Figure 26 can be
used. The signal from the microphone was measured under
actual conditions to vary from 1 mV to 15 mV. The postamplifier
requires no more than 500 mV at its input. The required gain
from the SSM2166 is, therefore
G
TOTAL
= 20 × log(500/15) = 30 dB
The input buffer gain is set to 20 dB, and the VCA gain is adjusted
to 10 dB. The limiting or rotation point is set at 500 mV output.
A 2:1 compression ratio and a noise gate threshold that operates
below 100 µV is also used. These objectives are summarized in
Table 5. The transfer characteristic implemented is illustrated in
Figure 30.
Table 5. Objective Specifications
Parameter Value
Input Range 1 mV to 15 mV
Output Range To 500 mV
Limiting Level 500 mV
Compression 2:1
Buffer Gain 20 dB
VCA Gain 10 dB
Noise Gate 100 μV