User Guide

NPM-10 (3595)
System Module CC Technical Documentation
Page 26 ©2004 Nokia Corporation Confidential Issue 2 03/2004
Battery Temperature Measurement A/D Channel (BTEMP)
The temperature of the battery pack is monitored during charging. The battery pack is
equipped with an NTC resistor (value is 47k Ohm at 25
o
C). The BTEMP signal is connected
on the baseband to the UEM. An external 100k Ohm pull-up is needed.
Battery Size Measurement A/D Channel (BSI)
This channel is used to identify the battery. The battery pack BLC-2 has a resistor
75k Ohm connected to ground. An external 100k Ohm pull-up resistor is on the phone
side. The BSI signal is connected to the UEM.
External Accessory Detection A/D Channel (HEADINT, HOOKINT)
An A/D converter channel is used to detect DCT4-type accessories. An A/D converter
channel is used to measure the DC level on the external microphone. The detection is
implemented using a pull-down resistor in the accessory and a pull-up on the baseband
side. The pull-up resistor on the baseband side is internal to the UEM. This A/D channel is
internally connected to either HeadInt or HookInt.
PA Temperature Measurement A/D Channel (
PATEMP)
This A/D channel is used for Cover Type Detection (CTI) in conjunction with DC-OUT
covers. The detection is implemented using a pull-down resistor in the accessory and a
pull-up on the baseband side.
LCD and Keyboard Backlighting
The backlighting is performed using Through the Board Side Firing (TBSF) white LEDs.
Two high-brightness LEDs are used to illuminate the LCD. The LEDs illuminate the light
guide where the light is distributed to generate sufficient backlight for the LCD. Two
regular-intensity LEDs are used to illuminate the keyboard.
Both sets of LEDs are driven using a constant current charge pump circuit (LM2795) as
shown in the following figure. The driver circuit is controlled by the UEM output pin
[DLIGHT]. Separate outputs are used for the LCD illumination (20 mA per LED), and a
shared output is used for Keyboard LEDs (10 mA). The LEDs can be dimmed by controlling
the PWM output of UEM.