User Guide

CCS Technical Documentation System Module
RH-25
Issue 1 10/2003 ©Nokia Corporation Confidential Page 11
Figure 4: UEM charging circuitry
Charger Detection
Connecting a charger creates voltage on the VCHAR input to the UEM. When the VCHAR
input voltage level rises above the VCHDET+ threshold, the UEM starts the charging pro-
cess. VCHARDET signal is generated to indicate the presence of the charger for the SW.
Energy Management (EM) SW controls the charger identification and acceptance.
The charger recognition is initiated when the EM SW receives a "charger connected"
interrupt. The algorithm basically consists of the following three steps:
1 Check that the charger output (voltage and current) is within safety limits.
2 Identify the charger.
3 Check that the charger is within the charger window.
If the charger is identified and accepted, the appropriate charging algorithm is initiated.
Charger Interface Protection
In order to ensure safe operation with all chargers and in mis-use situations, charger
+
-
VBATTlim
Comp
Switch
Driver
Ctrl
Logic
Over
Temp.
Detection
VCHARin
VCHARout
VBATT
V
CHAR
VBATT
UEM
Current
Sensing/
Limit
Vmstr
WatchDog