Microphone; Fig 5 Earpiece/Ringer Interface - Nokia RH-53 Manual

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UEM
EARP
EARN
HF
HFCM
UPP
GENIO14

Microphone

The acoustical design is copied from Nokia 7210 with some modifications. In comparison to
N7210, the microphone boot is a separate component placed next to the bottom connector.
The electrical Microphone design is a differential bias circuit, driven directly from the MICB1
bias output with external RC-filters. This is one solution that has previously been used with suc-
cess in other projects.
The RC filter (220 Ω, 4.7µF) is scaled to provide damping at 217 Hz. TDMA noise (217 Hz au-
dible noise) will occur if the bias output MICB1 demodulates in-coming radio frequencies.
Common DCT4 BB specifies filtering of the reference voltage for the microphone bias genera-
tors. In next figure this filtering is included on the MICBCAP pin. This capacitor will not be
mounted when the UEMc will be used.
The microphone bias is controlled in the 8 bit AudioBiasR register. The figure below shows the
electrical interface.
24
Figure 5:Earpiece/ringer interface
Interface to
external audio
1u
4k7
IN-
4k7
IN+
330p
BYPASS
470 n
SHUTDOWN
COMPANY CONFIDENTIAL
Copyright © 2004 Nokia. All Rights Reserved.
10
10
Vbat
33k
Vdd
Vo1
Vo2
GND
Placed near Placed outside
UEM BB-can, near the
connections to
MALT
RH-53/54
8-System Module
XEARP
XEARN
MALT
Interface to
DC-out
Not used / NA
ISSUE 1 09/2004