TM1215 Iss. 6.0 RPR750
3.2.4.3 Power management
This section comprises IC5 and IC10, under the control of IC1/IC12.
IC10, L1 and D29, form a voltage converter, which boosts the nominal battery voltage to
3.3V (VDD). When a battery is fitted, TR’s 8 & 10 are enabled and the output of IC10 is
connected to the digital sections of the pager.
The presence of the main battery is detected by TR8 (B+), which controls the status of
TR10. At the same time, the backup cell BATT2 is charged from the main battery, which
typically takes around 24 hours from flat. If the main battery fails or is removed, TR8 is
switched off, which status is signalled to IC1/IC12 (PFAIL). At the same time TR10 is
turned off, effectively isolating IC10 from the backup cell. BATT2 will maintain the internal
clock and message memory function for a minimum of 12 hours.
IC5 is a voltage detector, which controls the reset signal to IC1/IC12. When the supply line
(VDD) falls below 2.2V, IC5 triggers the (RESET) line to IC1/IC12, resulting in the pager
losing any messages and re-setting its real-time clock.
Also included within the power management section, are the driver for the vibrate motor
TR’s 2 & 3, the Alert LED driver TR6 and the display module backlight driver circuit
combination, TR9/L2.
The pager is charged via external contacts CONN1(CHG) + CONN1(GND ) and R54/D25
to the B+ rail. The presence of a charging voltage is signalled to IC1/IC12 by TR4
(CHGDET).
3.2.4.4 Programming
When programming the pager from an absence rack or programming pocket, serial data is
transferred from the external contact CONN1 (PROG) to the IC1/IC12 (PROGB) pin.
Resistor R38 provides a pull-down function to IC1/IC12 and the diode D26, provides ESD
and excessive voltage protection for the external programming contact.
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