Audio Amplifier And Malt Speaker; External Audio Interface - Nokia RH-47 Series Description
Hide thumbs
Also See for RH-47 Series:
- Rf description and troubleshooting (76 pages) ,
- Disassembly & assembly instructions (22 pages)
Table of Contents
Advertisement
Nokia Customer Care
capacitors. Microphone bias block in the UEM generates bias voltages for handportable
and handsfree/headset microphones. For both microphone bias outputs (MICB1 &
MICB2), the minimum output voltage is 2.0 Volts and maximum output current is 600
µA. Microphone bias block also includes a low pass filter for the reference voltage used
as an input for the MICB1&2 amplifiers.
Audio amplifier and MALT speaker
The speaker used in RH-47 is a 16mm 8Ω speaker. It can handle 0.2 Watts nominal
power and peak power 0.3 Watts. The component is housed in the B-cover and connects
to the PWB via spring contacts.
HF and HFCM lines of UEM are use to drive the amplifier.
Power amplifier is a differential opamp. The differential output drives the MALT speaker.
The amplifier load impedance is 8 ohm.
The outputs go into a high impedance state when powered down. The amplifier can be
enabled and shut down using a GENIO line from UPP_WD2.
SW controls IHF and earpiece volume via UEM. Gain setting can be done in 2 dB steps,
from –40 to +6 dB. Output sound pressure level of the MALT speaker is controlled by SW
(CBus is used for controlling).
The schematic around the amplifier is presented in RH-47 schematics. The schematic
shows all the filtering needed and also protection components against ESD and EMC.
The supply voltage for the amplifier is taken directly from the battery voltage.
External audio interface
In RH-47, there is headset connector which is a fully differential 4–wire connection.
2. XEARN
4. XEARP
5. HEADINT
3. XM ICP
1. XM ICN
The handsfree (HF) driver in the UEM is meant for a headset. In RH-47, the output is
driven in fully differential mode. In the fully differential mode, the HF pin is the negative
output and HFCM pin is the positive output. The gain of the handsfree driver in the dif-
ferential mode is 6 dB. The earpiece (EARP, EARN) and headset (HF, HFCM) signals are
multiplexed so that the outputs can not be used simultaneously. The HF and HFCM
amplifiers include a transient suppression circuitry.
The plug opens a mechanical switch inside the connector between HF and HeadInt lines.
The HeadInt line is pulled up to 2.7V by internal resistor when the switch is open. When
Issue 1 05/04
Company Confidential
6 - Baseband Description and Troubleshooting
Figure 5: External Audio Connector
Copyright © 2004 Nokia Corporation
Company Confidential
RH-47
Page 17
Advertisement
Table of Contents
Troubleshooting
