User Guide

RH-23 Company confidential
System Module and User Interface CCS Technical Documentation
Page 38 Nokia Corporation. Issue 1 02/2004
IHF Speaker & Stereo Audio Amplifier
Integrated Hands Free Speaker, 16mm MALT, is used to generate speech audio, alerting
and warning tones in RH-23. Audio amplifier is controlled by the UPP. Speaker capsule is
located in upper block and is mounted in the antenna-cover. Spring contacts are used to
connect the IHF Speaker contacts to the upper block FWB.
Figure 20: Block Diagram of Audio amplifier
The LM4855 features a 32-step digital volume control and eight distinct output modes.
The digital volume control and output modes are accessed through a three-wire inter-
face, controlled by UPP. Digital volume control is needed when FM radio is activated;
there is no amplifier block in FM radio module. Output modes are needed when routing
audios to different locations; Headset or IHF.
Table 36: IHF Speaker signal characteristics
Signal Min Nom Max Condition Note
XEARN (out-) 0.75V 0.8V 2.0 Vpp
0.85V
AC
DC
Differential output
(Vdiff = 4.0Vpp)
XEARP (out+) 0.75V 0.8V 2.0 Vpp
0.85V
AC
DC
Output
Mode
Select
Digital
Volume
Control
Bias
Bypass
Rin
Lin
EN CLK DAT
A
Lout -
Lout +
Rout -
Rout +
out -
out +
VBAT
GND
Phone
audio
Cs
=
1uF
Radio audio
IHF Speaker
Radio audio
Stereo Headset
Amplifier
Amplifier
Amplifier
Amplifier
Amplifier
Amplifier