User Guide

Nokia Customer Care System Module

Company Confidential RH-30/RH-31

Backup battery

Backup battery is used in case when main battery is either removed or discharged.

Backup battery is used for keeping real-time clock running for minimum of 30 minutes.

Rechargeable backup battery is connected between UEM VBACK and GND. In UEM

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 2: Backup Battery circuitry

Parameter

Test conditions

Symbol Min Typ Max Units

Back-up battery voltage VBACK 2.43 3.3 V

Back-up battery cut-off limit V_BU

COFF+

V_BU

COFF-

2.04

1.94

2.10

2.0

2.16

2.06

Charging voltage (VBAT ≥ 3.4V)

VBU 3.1 3.2 3.3 V

Charging current I

LIMVBU

150 500 mA