Backup Battery - Nokia NSB-9 Service Manual

CCS Technical Documentation
Signal name Pin number
VBAT 1
BSI 2
BTEMP 3
GND 4
The BSI fixed resistor value indicates type and default capacity of a battery. NTC-resistor
BTEMP measures the battery temperature.
Temperature and capacity information are needed for charge control. These resistors are
connected to BSI and BTEMP pins of battery connector. Phone has 100 kΩ pull-up resis-
tors for these lines so that they can be read by A/D inputs in the phone.

Backup Battery

Backup battery is used in case when main battery is either removed or discharged.
Backup battery is used to keep real-time clock (RTC) running for minimum of 30 minutes.
Rechargeable backup battery (capacitor type) is connected between UEM VBACK and
GND. In UEM backup battery charging high limit is set to 3.2V. The cut-off limit voltage
(VBUCoff-) for backup battery is 2.0V. Backup battery charging is controlled by MCU by
writing into UEM register. Battery is not charged during power off.
Parameter
Test conditions
Back-up battery voltage
Back-up battery cut-off limit
Charging voltage (VBAT ≥ 3.4V)
Charging current
Issue 1 04/03
Table 27: Pin numbering of Battery Pack
Function
Positive battery terminal
Battery capacity measurement (fixed resistor inside the battery pack)
Battery temperature measurement (measured by ntc resistor inside pack)
Negative/common battery terminal
Figure 8: Battery Pack contents
4(GND) 3(BTEMP)
Table 28: Back-up circuity
Symbol
VBACK
V_BU
COFF+
V_BU
COFF-
VBU
I
LIMVBU
Nokia Corporation
System Module and User Interface
2(BSI) 1 (+)
Min Typ
2.43
2.04 2.10
1.94 2.0
3.1 3.2
150
NSB-9
Max Units
3.3 V
2.16 V
2.06 V
3.3 V
500 mA
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