Charge Control; Audio; Display And Keyboard - Nokia RH-3 Series Troubleshooting - Bb

RH-3
Troubleshooting — BB

Charge Control

In active mode charging is controlled by UEM's digital part. Charging voltage and current
monitoring is used to limit charging into safe area. For that reason UEM has programma-
ble charging cut-off limits:
VBATLim1=3.6 V (Default)
VBATLim2L=5.0 V and
VBATLim2H=5.25 V.
VBATLim1, 2L, 2H are designed with hystereses. When the voltage rises above VBATLim1,
2L, 2H+ charging is stopped by turning charging switch OFF. No change in operational
mode is done. After voltage has decreased below VBATLim- charging re-starts.
There are two PWM frequencies in use depending on the type of the charger: two-wire
charger uses a 1Hz and a three-wire charger uses a 32Hz. Duty cycle range is 0% to
100%. Maximum charging current is limited to 1.2 A.

Audio

The audio control and processing in RH-3 is provided by UEM, which contains the audio
codec, and UPP — which contains the MCU and DSP blocks, handling and processing the
audio data signals.
The baseband supports three microphone inputs and two earpiece outputs. The micro-
phone inputs are MIC1, MIC2, and MIC3. MIC1 input is used for the phone's internal
microphone; MIC2 input is used for headsets (HDB-4, BHF-1. and CarK-126), Loopset
(LPS-4). MIC3 input is used for third-party accessories (2.5mm Jack). Every microphone
input can have either a differential or single ended ac connection to UEM circuit. In
RH-3, the internal microphone (MIC1) and MIC2 are differential and MIC3 microphones
are single-ended. The microphone signals from different sources are connected to sepa-
rate inputs at UEM. Inputs for the microphone signals are differential type. Also,
MICBIAS1 is used for MIC1 and MICBIAS2 is used for MIC2 and MIC3.

Display and Keyboard

LEDs are used for LCD and keypad illumination in RH-3. There are three LEDs for LCD and
four LEDs for keypad. The LEDs are supplied by a driver circuit which consists of a charge
pump and several current source, which are partly integrated into the driver and partly
realized by discretes.
A monochrome LCD is used in RH-3. Interface is using 9-bit data transfer. The interface
is quite similar to DCT3 type interface, except Command/Data information is transferred
together with the data. D/C bit set during each transmitted byte by MCU SW.
Figure 17 on page 21 is the waveform for LCD interface.
Page 20
Nokia Corporation
CCS Technical Documentation
Confidential Issue 1 06/2003