MB86437 Datasheet, PDF (15/35 Pages) Fujitsu Component Limited. – 3 V Single Power Supply Audio Interface Unit (AIU)

MB86437
2. Analog Input
Analog inputs in the MB86437 include the two microphone inputs and the three accessory input.
(1) Microphone amps
The microphone amps take the incoming signal from the microphones and amplify it to any desired level of gain.
The microphone amps are low-noise types for use with capacitor microphones, and are capable of a wide range of
amplification. All microphone amps must be AC coupling with capacitors to prevent amplification of DC offset level.
Mike amplifier characteristics (open loop characteristics)
80
40
0
–40
10
1K
1M
Frequency (Hz)
MICO
MIC
XMIC
(Inside IC)
V DD
SGC
Capacitor type
Mike
AG
(2) Accessory input
Direct input from the TAUD to the codec unit is possible through SW5, without passing through the microphone
amp. Care must be taken with the input signal in this case, however, because input resistance is not at high-
impedance level.
Microphone amp output may be added to the signal by using switching controls.
In this case, the result will be at the additional output level.
In addition, SW10 and SW11 may be used to transmit digital data from the TAUD to EXSD and DSCK, allowing the
sending of fax or PC data without modification.
CODEC
0 dB
Approximately 100 kΩ
SW5
SW10
SGC
SW11
(Inside IC)
TAUD
EXSD
DSCK
Note: TAUD, EXSD, and DSCK contain no buffers. If not used,
TAUD, EXSD and DSCK should be connected to SGC.
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