Nokia RH-9 Series Ccs Technical Documentation page 36

RH-9
System Module & UI
audible noise (TDMA) 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
generators. In below figure this filtering is included on the MICBCAP pin.
Besides pure bias purposes also EMC and ESD protection is shown in figure 11. The RC-
filter 2.2 kΩ and 1nF are EMC-component, while the remaining 10 nF and 1 nF capaci-
tors near the bottom connector are for ESD.
The 33nF and 100nF series-capacitors and 12kΩ parallel resistor create a 2'nd order high
pass filter. The input impedance of the gain stage at MIC1P/N is part of the 2'nd stage of
the RC-circuit. The high pass filter is required due to low-frequency noise, which is one
phenomenon identified as a problem when the internal microphone is used as handsfree
microphone (PPH-1/carkit mode).
The microphone bias is controlled in the 8 bit AudioBiasR register.
UEM
MICB1
MIC1P
2*33n
MIC1N
MICBCAP
1u
Ringer
A speaker is used to generate alerting tones and melodies to indicate incoming call, as
well as used to generate game sound, keypress and warning tones for the user
A new type of component is used for ringer melodies: a speaker.
The speaker is a 13 mm device from PSS. It's inherited from the 13mm earpiece (also
used by NHM-8) however with more height to provide opportunities for more displace-
ment for the speaker diaphragm. The speaker have a protective shield directly in front of
the diaphragm.
The speaker substitutes the original buzzer.
Alerting tones and MIDI melodies is generated by the speaker, which is controlled by a
Page 36
Figure 9: Internal microphone electrical interface
220 1k
4.7uF
2*100n
1n 1n
ãNokia Corporation
CCS Technical Documentation
Placed near
Placed near
bottom
UEM
connector
2k2
2k2
10n 10n
MIC+
1n
MIC-
Issue 1 11/02