TSH512 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TSH512' PDF : 32 Pages View PDF
General description
Figure 27. Electret condenser microphone source
TSH512
The capacitor C in series with the microphone stops the DC coming from MIC-BIAS.
The resistor R provides the DC from MIC-BIAS to supply the ECM.
Thanks to the automatic level control (ALC), the great variations of amplitude will not over-
modulate the transmitter (refer to the Section 5.4: ALC section: automatic level control).
The self-adaptive VOX (voice operated transmit) offers automatic transmitting with a good
discrimination of the background noise (see Section 5.5: VOX description: voice operated
transmit on page 21).
5.3
MIC-BIAS section: microphone bias voltage
The MIC-BIAS bias voltages are dedicated to the bias of electret condenser microphones.
These bias voltages on pin 10 for TX1 and pin 2 for TX2 exhibit a low voltage noise density
of 22 nV/√Hz). This allows more than 55 dB S/N considering a bandwidth of 7 kHz
(Figure 27).
The MIC-BIAS voltage is related to VCC as follows (with I MIC-BIAS= 2.5 mA):
VMIC-BIAS = 0.844.Vcc-0.140 (volts)
Moreover, the supply rejection ratio is guaranteed to be better than 50 dB without any
decoupling capacitor. To address biasing of most of the microphones, the current drive
capability is 2.5 mA. The MIC-BIAS voltage depends linearly on the supply voltage VCC
(refer to Figure 11 on page 11).
20/31
Doc ID 8120 Rev 7
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