User Guide

Nokia Customer Care System Module and User Interface
NPL-4/5
Issue 1 05/04 Copyright © 2004 Nokia Corporation. All rights reserved. Page 39
Figure 9: Ambient Temperature Sensor Interface to BB
Backup battery
Backup battery is used in case when main battery is either removed or dis-charged.
Backup battery is used for keeping realtime clock running for minimum of 30 minutes.
Rechargeable backup battery is connected between UEMEK VBACK and GND. In UEMEK
backup battery charging high limit is set to 3.2V. The cut–off limit voltage (V BUCoff– )
for backup battery is 2.0V.
Backup battery charging is controlled by MCU by writing into UEM register. Li-Ion SMD
battery type is used. The nominal capacity of the battery is 0.01 mAh.
Table 20: Backup Battery Circuitry
SIM interface
The UEMEK contains the SIM interface logic level shifting. The SIM interface can be pro-
grammed to support 3V and 1.8V SIM. A register in the UEMEK selects SIM supply volt-
VANA
R211, 12k
5%
R212, 68k
1%
R101,10k
NTC 1%
Headint2
A
uxDet
UI board
UEMEk
A
/D
MUX
Slow
A
DC
Parameter
Test conditions
Back-up battery
voltage
VBACK 2.43 3.3 V
V_BU
COFF+
2.04 2.1 2.16 V
V_BU
COFF-
1.94 2 2.06 V
Charging voltage
(VBAT 3.4V)
VBU 3.1 3.2 3.3 V
Charging current I
LIMVBU
150 500 uA
Typ Max Units
Back-up battery
cut-off limit
Symbol Min