BGS3 Hardware Interface Description
3.11 Audio Interfaces
63
BGS3_HD_v01.000d
Page 53 of 109
2010-03-26
Confidential / Released
3.11.2.1
Single-ended Microphone Input
as well as
show an example of how to integrate a single-ended microphone
input.
R
A
has to be chosen so that the DC voltage across the microphone falls into the bias voltage
range of 1.0V to 1.6V and the microphone feeding current meets its specification.
The MICNx input is automatically self biased to the MICPx DC level. It is AC coupled via C
K
to
a resistive divider which is used to optimize supply noise cancellation by the differential micro-
phone amplifier in the module.
The VMIC voltage should be filtered if gains larger than 20dB are used. The filter can be at-
tached as a simple first order RC-network (R
VMIC
and C
F
).
This circuit is well suited if the distance between microphone and module is kept short. Due to
good grounding the microphone can be easily ESD protected as its housing usually connects
to the negative terminal.
R
A
= typ. 2k
R
B
= typ. 5k
R
VMIC
= typ. 470Ohm
C
k
= typ. 100nF
C
F
= typ. 22µF
V
MIC
= typ. 2.5V
V
bias
= 1.0V … 1.6V, typ.
1.5V
Figure 16:
Single ended microphone input
