User Guide

PAMS
Technical Documentation
RAE–2
BS1
Page 5 – 21
Section 02/99
controls the LCD, MMC, and IR–transceiver logic voltages by writing com-
mand to the PWRU register. Optionally the CPU can control the LCD log-
ic- and biasing voltage directly by means of I/O signals.
The backup battery supplies power to the CPU’s real time clock. The
PWRU charges the backup battery when the main battery is connected.
The CPU puts the Flash memories to power down mode when they are
not used.
The BS8 signal BATTDET is a warning signal that the battery will be re-
moved soon, when power down procedure is started. VBB is the supply
voltage for the CMT display, located in the BS2 module, and the VBB
provides information for the BS1 CPU whether the CMT powered or not
and it enables the keyboard buffer. The MMC_SWITCH indicates that the
MMC card will be removed, when the CPU controls the Phaser to turn the
V28_3 off.
Input filter
The Battery voltage is fed from the BS8 module and then filtered by using
a LC–lowpass filter, after filtering the voltage is named VPDA. The VPDA
is then fed to the PWRU, the IR–transceiver, the PHF–speaker circuitry,
and to the BS2 module.
Linear regulator V28
System voltage V28 is generated by a linear regulator. V28 stays on all
the time when the battery voltage is higher than cutoff limit.
Linear regulator V28_1,_2,_3
These regulators are controlled by the CPU. The CPU can enable these
regulators by writing a command to the PWRU’s register. V28_1 is the
switched V28 and is used for the LCD logic. V28_2 is the switched V28
and is used for the IRDA logic. V28_3 is the MMC voltage.
Switchmode regulator V17
The LCD bias voltage V17 is generated by a step–up DC–DC converter.
The control scheme is the current limited pulse width modulation (PWM).
The switching transistor is internal. The regulator output, too, is sepa-
rated from the battery line by an integrated switch transistor between the
regulator output and load.
Backup battery
The Real time clock is kept running by a backup battery only when the
main battery is not connected. At the nominal RTC load used , the
12mAh capacity of the backup battery provides about 40 days of RTC op-
eration when the main battery is not connected. The backup battery is