Charge Control; Audio; Display And Keyboard - Nokia RH-44 Series Troubleshooting - Bb

RH-44
Troubleshooting — BB

Charge Control

In active mode, charging is controlled by UEM's digital part. Charging voltage and cur-
rent monitoring is used to limit charging into safe area. For that reason, UEM has pro-
grammable 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 occurs. After voltage has decreased below VBATLim-, charging re-starts.
Two PWM frequencies are used, depending on the type of charger: two-wire charger uses
a 1 Hz and three-wire charger uses a 32 Hz. Duty cycle range is 0% to 100%. Maximum
charging current is limited to 1.2 A.

Audio

UEM handles the audio control and processing, including the audio codec. UPP, which
contains the MCU and DSP blocks, handles and processes the audio data signals.
The baseband supports three microphone inputs and two earpiece outputs. The micro-
phone inputs are MIC1, MIC,2 and MIC3. MIC1 input is used for the phone's internal
microphone; MIC2 input is used for headsets (HDB-4, BHF-1, and CARK-142), and
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. The internal microphone (MIC1) and MIC2 are differential and MIC3 microphone
is single-ended. The microphone signals from different sources are connected to separate
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.
The HF single-ended output is sent to the input of the MIDI audio amplifier. The amplifier
can be enabled/disabled by GenIO(28). The gain of the amplifier is about 20dB.

Display and Keyboard

LEDs are used for LCD and keypad illumination. There are four LEDs for LCD and two LEDs
for the keypad.
Color LCD is used. Interface uses 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.
The following figure is the waveform for LCD interface.
Page 20
Nokia Corporation
CCS Technical Documentation
Confidential Issue 1 04/2003