User Guide

PAMS Technical Documentation 10. Troubleshooting
NSD-5
Issue 1 05/02 Nokia Corporation Page 5
Troubleshooting
Baseband Troubleshooting
Each main portion of the circuit will be described in enough detail for the troubleshooter
to determine whether or not that part of the circuit being evaluated is functional. It will
be helpful to use the placement diagram, which illustrates all of the necessary testpoints
in the baseband circuit, to troubleshoot the phone. The placement diagram is intended to
be used concurrently with this document. Herein, TPD refers to Test Point Designation.
Main Circuit Sections
Power Circuitry
There are two ASICs in the baseband section, which supply power to most of the phone.
CCONT is the main power management ASIC. Two discrete linear regulators are used as
well.
CCONT
CCONT is the main power management ASIC. Its features include eight 2.8V linear regu-
lators, a linear regulator with adjustable output, a reference voltage output, a 5V switch
mode regulator, an 8-channel A/D converter, and 32kHz clock circuitry. Each of the main
functions and signals is described below, including information on how to verify correct
operation.
Vbat
CCONT is powered directly from the battery voltage (Vbat). Since CCONT is a uBGA, the
physical connection of CCONT’s power pins cannot be verified. Vbat must be checked
instead at the closest external component, which is shown as TPD. Valid voltages are
3.2 – 4.2V and should always be powered, assuming voltage is applied to the
battery terminals.
Vref
Vref is used as a reference voltage both internal and external to CCONT. It is switchable
between the nominal voltages of 1.500V and 1.251V, with the default at power-up being
1.500V. The phone uses the 1.251V reference, so once flash software is running, Vref
should switch to 1.251V.
Check Vref at TPD. Valid voltages are 1.478 – 1.523V and 1.244 – 1.258V, respectively.
Linear Regulators
1. Vbb
Vbb supplies power to most of the baseband circuitry. This regulator should be on at all
times during CCONT’s power on, reset, and sleep modes. Nominal voltage is 2.8V, but
anything in the range 2.7 – 2.87V is valid. Vbb is found at TPD30.