Acoustics - Nokia RH-6 Series Baseband Description & Troubleshooting

RH-6
6 - BB Description & Troubleshooting
also needed to other side of the microphone, i.e. between microphone and GND, in order
to provide the differential signals to UEM. Audio signals are AC-coupled from the micro-
phone.
For the external microphone a differential input is used.
MIC1N & MIC1P (audio signals) and MICB1 (bias voltage) are used for the internal
microphone. MIC2N & MIC2P and MICB2 are used for external microphone.
Integrated Hands-free (IHF)
The speaker used for IHF is a 16 mm diameter speaker with 8 Ohm impedance, and is also
known as "MALT" speaker.
IHF circuitry uses differential outputs from UEM.
Depending on the audio mode the IHF amplifier is driven either from UEM HF / HFCM or
XEAR audio outputs. The IHF audio power amplifier (APA) LM4890 has a bridge-tied-load
(BTL) output in order to get the maximum use of supply voltage. The supply voltage for
driving circuitry of speaker is VBAT, thus the swing across the speaker is (VBAT.
The shutdown of the IHF PA is controlled by UPP using GENIO14.
Audio accessory receive path
In RH-6 the accessory receive path is directly driven from UEM HF / HFCM differential
audio outputs, the output signal complies with the Pop-port accessory interface.
For EMC protection ferrites are connected in series to the earpiece, for ESD protection
varistors are used.
Audio control signals
Furthermore, a couple of signals are needed to control the external audio device.
The HEADINT signal is needed for recognizing the external device (e.g. headset) con-
nected to the system. The recognition is based on the ACI-pin on the system connector,
which is shorted to ground inside the external device.
The button of the external device generates HOOKINT. This is used e.g. to answer or to
end a phone call.

Acoustics

Earpiece acoustics
RH-6 uses the so called "PICO" earpiece.
This earpiece is mounted into the UI-shield assembly, the sealing of the back and front
volume are implemented in the UI-shield by die casting. This sealing part also provides
the sealing against the A-cover.
Page 18
Company Confidential
© 2003 Nokia Corporation.
CCS Technical Documentation
Issue 1 10/2003