User Guide

NSD-5
10. Troubleshooting PAMS Technical Documentation
Page 8 Nokia Corporation Issue 1 05/02
1Hz or at 32Hz, with varying duty cycles, and should only be active when a charger is
detected. The frequency depends on charger type. To verify correct operation of CHAPS,
monitor the charging current (ICHAR) with the service software. When the PWM is off,
current should be approximately 200uA. When the PWM is on, it must be greater than
approximately 300mA.
CAFE
The CAFE ASIC performs various functions with respect to the RF circuitry and audio. It
digitizes the analog voice signals from the microphone as well as converts received digi-
tal data to voice signals to be sent to the earpiece. This also includes accessory micro-
phones and speakers. It also generates and decodes I and Q data for CDMA signals. CAFE
also acts as a clock squaring circuit and CDMA clock generator.
Microphones
The internal microphone is biased using transistor V280, which is powered by VR1_SW.
MICP should be about 1.7VDC, and MICN should be about 0.4VDC. Internal microphone
bias should only be active during a call. The XMIC is biased by the AUXOUT signal
through R240 and R241. The AUXOUT output provides 1.5V bias voltage to the external
microphone.
Earpiece and XEAR
The internal earpiece is driven differentially (EARP and EARN). The DC voltage on these
two pins is 1.35V. The difference in the DC voltage between these two pins should not be
more than 50mV.
The XEAR signal drives audio to the external accessories. The CAFE signal name is HF. The
DC level on this pin should be 1.35V. HFCM should also be at 1.35V. The difference in DC
voltage between these two pins should not be more than 50mV.
Note that SGND is the return path for XMIC and XEAR.
Transmit and Receive RF Signals
In CDMA mode, receive I and Q channel RF signals [RXIQ(3:0)] come into CAFÉ pins.
C201, C202, C203, and C204 can also be checked for these signals since they are in series
with the CAFÉ pins. Transmit I and Q RF signals [TXIQ(3:0)] can be seen at C205, C206,
C207, and C208.
MAD4
The MAD4 ASIC is the core of the baseband functionality and basically contains the DSP,
MCU, and CDMA logic. The DSP is used to perform functions such as RF control, DTMF
tone generation, and implementation of the vocoder. The MCU is used to perform func-
tions that do not require as much power — higher-level functions such as UI software
(key presses, backlighting, LCD functions, etc.) and mode control.
DSP
The DSP sends control signals to the RF via PDMs. In order to control RF parameters such
as TX_LIM_ADJ, a continuously variable analog signal must be used. Since the DSP out-