6.3.6. SRAM and RTC BACK UP CIRCUIT
1. Function
This unit has a lithium battery (BAT1) which works for the RAM (IC4) and Real Time Clock (RTC, Integrated into ASIC:IC1).
The user parameter for auto dial numbers, the transmission ID, the system setup date and so on are stored in the RAM (IC4).
The RTC continues functioning, even when the power switch is OFF, backed up by a lithium battery.
2. Circuit Operation
When the power is turned ON, power is supplied RAM (IC4) and RTC (IC1).
At this time, the voltage at pin 28 of RAM is +5V and pin 7 of RTC (IC1) is +3.3V. When the power is turned OFF, the battery
supplies the power to RAM and RTC through J1, R24, D1 or DA1. At that time, the voltage at pin 28 of RAM and pin 7 of IC1
are about +2.5V. When the power is OFF and the +5V and +3.3V voltages decrease, IC3 detects them and LOW is input to pin
112 of IC1. Pin 109 of IC1 outputs the reset signals. Pin 28 of RAM (IC4) and pin 11 of IC1 become low, then RAM and RTC
(IC1) go into the back up mode, when the power consumption is lower.
107
KX-FT63BX / KX-FT63BX-W
To Next Page
Loading...
