Baseband Testing; Alignments - Nokia NSB-7 Series Service Manual

PAMS Technical Documentation
means of inductors in the power supply rail to prevent high frequency components pro-
duced on the baseband power supply rail to spread out over the RF power supply plane.
This might be required to avoid interference from digital circuits to affect the perfor-
mance of RF section.
All external connectors and connection must be filtered using RC or LC networks to pre-
vent the high frequency components from entering connection cables that then will act
as antennas. The amount of this type of EMC component is in straight relation to the
amount of external connections. The type of network and amount of components to be
used is determined by the AC and DC impedance characteristic of that particular signal.
Low impedance signals requires LC network while medium impedance level signals, input
signals at moderate band width can use RC networks.
The EMC protection should also prevent external or internal signals to cause interference
to baseband and in particular to audio signals. Internal interference is generated by the
transmitter burst frequency and the switchmode charging. The transmitter burst fre-
quency interference is likely to cause noise to both microphone and earphone signals.
The transmitter RF interference is likely to cause more problems in the microphone cir-
cuitry than in the earphone circuitry since the earpiece is a low impedance dynamic type.
As mechanical guide lines, the baseband and RF sections should be isolated from each
other using EMC shielding, which suppresses radiated interferences. The transmitter
burst frequency can also generate mechanical vibrations that can be picked up by the
microphone if it is not properly isolated from the chassis using rubber or some other soft
material. Connection wires to internal microphone and earphone should be as short as
possible to reduce the interference caused by internal signals.
ESD protection has to be implemented on each external connection that is accessible
during normal operation of the phone.

Baseband Testing

The MCU software enters a local mode at startup if a dummy battery is attached and the
battery temperature value is high enough. This means that the fixed resistor on the
BTEMP line must correspond to a temperature higher than +85 C. In the local mode the
baseband can be controlled through MBUS or FBUS connections by a PC-locals software.
Baseband internal connections are tested with self tests if possible. By connecting MAD2
pin ROW5 to ground, MAD2 pins are toggled as a daisy chain, which can be used for
detecting short circuits in MAD2 pins. Test pads will be placed on engine pcb for service
and production trouble shooting purposes in some supply voltage and signal lines.

Alignments

Within alignment those parameters are adjusted, that cannot be set accurate enough by
design, because of component tolerances.
Due to use of 5% resistor values, the channels of the CCONT A/D converters need to be
aligned in the production phase.
Within battery voltage VBATT tuning the MCU software reads the A/D reading from
Issue 1 06/00 ãNokia Mobile Phones Ltd.
NSB-7
System Module
Page 41