User Guide

CC Technical Documentation System Module
NPM-10 (3595)
Issue 2 03/2004 ©2004 Nokia Corporation Confidential Page 23
Whenever VBAT level is detected to be below master reset threshold (V
MSTR-
), charging is
controlled by START_UP charge circuitry. Connecting a charger forces VCHAR input to
rise above charger detection threshold, VCH
DET+
. By detection start-up charging is
started. UEM generates 100 mA constant output current from the connected charger’s
output voltage. As the battery charges, its voltage rises, and when the VBAT voltage level
is higher than the master reset threshold limit (V
MSTR+
) is detected and the START_UP
charge is terminated.
The charge control block (CHACON) monitors the VBAT voltage level. MSTRX=‘1’ output
reset signal (internal to UEM) is given to UEM’s RESET block when VBAT>V
MSTR+
and the
UEM enters into a reset sequence described in the Power Up and Reset section.
If VBAT is detected to fall below V
MSTR-
during start-up charging, charging is cancelled.
It will restart if new rising edge on VCHAR input is detected (VCHAR rising
above VCH
DET+
).
Power Up - Battery is Connected
Baseband can be powered up by connecting a battery with sufficient voltage. Battery
voltage has to be higher than the UEM internal comparator threshold level, V
coff+
. When
battery proper voltage is detected, the UEM enters the reset sequence as described in the
Power Up and Reset section. This power up sequence is meant for test purposes; in
normal use (Btemp resistor > 1kΩ) the phone will power off again immediately, without
noticing the user.
RTC Alarm Power Up
If the phone is in POWER_OFF mode when RTC alarm occurs, the wake up procedure is as
described in the Power Up and Reset section. After the baseband is powered on, an
interrupt is given to MCU. When the RTC alarm occurs during ACTIVE mode, the interrupt
for MCU is generated.
A/D Channels
The UEM contains the following A/D converter channels that are used for several
measurement purposes. The general slow A/D converter is a 10-bit converter using the
UEM interface clock for the conversion. An interrupt will be given at the end of the
measurement.
The UEM’s 11-channel analog-to-digital converter is used to monitor charging functions,
battery functions, voltage levels in external accessory detection inputs, user interface,
and RF functions.
When the conversion begins, the converter input is selected. Then the signal processing
block creates a data with MSB set to ’1’ and others to ’0’. In the D/A converter, this data
controls the switches, which connect the input reference voltage (VrefADC) to the
resistor network. The generated output voltage is compared with the input voltage under
measurement and if the latter is greater, MSB remains ’1’ else it is set ’0’. The following
step is used to test the next bit and the next, until LSB is reached. The result is then
stored to the ADCR register for the UPP to read.