Nokia RH-47 Series Description

Also see for RH-47 Series: Rf description and troubleshooting Disassembly & Assembly Instructions

Contents

Nokia Customer Care 6 - Baseband Description and TroubleshootingCompany Confidential RH-47Issue 1 05/04 Copyright © 2004 Nokia Corporation Page 17Company Confidentialcapacitors. Microphone bias block in the UEM generates bias voltages for handportableand handsfree/headset microphones. For both microphone bias outputs (MICB1 &MICB2), the minimum output voltage is 2.0 Volts and maximum output current is 600μA. Microphone bias block also includes a low pass filter for the reference voltage usedas an input for the MICB1&2 amplifiers.Audio amplifier and MALT speakerThe speaker used in RH-47 is a 16mm 8Ω speaker. It can handle 0.2 Watts nominalpower and peak power 0.3 Watts. The component is housed in the B-cover and connectsto 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 beenabled 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 schematicshows 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 interfaceIn RH-47, there is headset connector which is a fully differential 4–wire connection.Figure 5: External Audio ConnectorThe handsfree (HF) driver in the UEM is meant for a headset. In RH-47, the output isdriven in fully differential mode. In the fully differential mode, the HF pin is the negativeoutput 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 aremultiplexed so that the outputs can not be used simultaneously. The HF and HFCMamplifiers 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. When2. XEARN4. XEARP5. HEADINT3. XM ICP1. XM ICN