RV-3029 Datasheet, PDF (22/67 Pages) MICORO CRYSTAL SWITZERLAND – DTCXO Temperature Compensated Real Time Clock

Micro Crystal
DTCXO Temperature Compensated Real Time Clock / Calendar Module
RV-3029
4.1.1.POWER UP SEQUENCE
The device can be either powered up from main supply V_DD or from backup supply V_BACKUP.
During power-up, the chip is executing the following power-up procedure:
• The implemented battery switchover circuitry compares V_DD and V_BACKUP voltages and connects the higher
of them to supply the chip
• At power-up, the chip is kept in Reset state until the supply voltage reaches an internal threshold level.
Once the supply voltage is higher than this threshold level, a Reset is executed and registers are loaded
with the Register Reset Values described in section 4.2.2. REGISTER RESET VALUES
• After the Reset is executed and registers are loaded with the Register Reset Values, “PON” is set = “1” (bit
5 in Register Control-Status), it needs to be cleared by writing = “0”
• Once the supply voltage reaches the oscillator start-up voltage, the oscillator-circuitry starts the 32.768 kHz
“tuning-fork” Crystal typically within 500 ms
• Once the 32.768 kHz clocks are present, the Voltage Detector starts in fast mode to monitor the supply
voltage, the accelerated scanning of the supply voltage will slightly increase the current consumption.
• When a supply voltage >V_Low2 is detected, the fast mode voltage detection is stopped, and the EEPROM
read is enabled
• Configuration registers are loaded with the configuration data read from the EEPROM Control Page and
the bits V_Low1 and V_Low2 are reset = “0”
• If the Thermometer is enabled by “ThE” = “1” (bit 1 in register EEPROM_Control), the temperature is
measured and the frequency compensation value for time correction is calculated
• The RV-3029 becomes fully functional; the correct Time / Date information needs to be loaded into the
corresponding registers and bit 5 “PON” in Register Control-Status needs to be cleared by writing “0”
Note 1:
During power up, the Low Voltage Detection is monitoring the supply voltage at an accelerated scan rate
increasing the current consumption of the device.
Once power supply voltage exceed V_LOW2 threshold, the flags V_LOW1 and V_LOW2 are cleared and the scan rate for
the low voltage detection is set to 1 second to ensure optimized power consumption.
Note 2:
Please not the different meaning of the “PON”; “V_Low1” and “V_Low2” Flags:
PON
“PON” Flag is set after Power-Up Reset is executed
• Indicating that time & date information are corrupted
V_Low1
V_Low1 Flag is set when supply voltage drops below V_Low1 threshold
• Indicating that the Thermometer might have been disabled due to low supply voltage and the temperature
compensation was operating for a while with the last temperature reading causing bigger time-deviation
V_Low2
V_Low2 Flag is set when supply voltage drops below V_Low2 threshold
• Indicating a risk that the 32.768kHz might have stopped due to low supply voltage and that the time & date
information might be corrupted
22/67