TS472_06 Datasheet, PDF (17/24 Pages) STMicroelectronics – Very low noise microphone preamplifier with 2.0V bias output and active low standby mode

TS472
Application information
Figure 37 below gives other values of the gain vs. voltage applied on GS pin.
Figure 37. Gain vs. gain select voltage
40
20
0
-20
-40
-60
-80
0
0.2
0.4
0.6
0.8
V (V)
GS
Tamb=25°C
4
5
5.6
Wake-up time
When the standby is released to put the device ON, a signal appears on the output a few
microseconds later, and the bypass capacitor C_b is charged in a few milliseconds. As C_b is
directly linked to the bias of the amplifier, the bias will not work properly until the C_b voltage
is correct.
In the typical application, when a biased microphone is connected to the differential input via
the input capacitors (C_in), (and the output signal is in line with the specification), the wake-up
time will depend upon the values of the input capacitors C_in and the gain. When gain is
lower than 0dB, the wake-up time is determined only by the bypass capacitor C_b, as
described above. For a gain superior to 0dB, see Figure 38 below.
Figure 38. Wake-up time in the typical application vs. input capacitors
60
Tamb = 25°C
Vcc=3V
50 _Cb=1μF
Maximum Gain
40
Gain=20dB
30
20
10
0
20
40
60
80
100
Input capacitors C (nF)
IN
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