RV-3049 datasheet(22/65 Pages) MICROCRYSTAL

22 / 65 page

Micro Crystal

DTCXO Temperature Compensated Real Time Clock / Calendar Module

RV-3049

22/65

4.1.1.POWER UP SEQUENCE

The device can be either powered up from main supply VDD or from backup supply VBACKUP.

During power-up, the chip is executing the following power-up procedure:

•

The implemented battery switchover circuitry compares VDD and VBACKUP 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 >VLow2 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 VLow1 and VLow2 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-3049 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 VLOW2 threshold, the flags VLOW1 and VLOW2 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”; “VLow1” and “VLow2” Flags:

PON

“PON” Flag is set after Power-Up Reset is executed

•

Indicating that time & date information are corrupted

VLow1

VLow1 Flag is set when supply voltage drops below VLow1 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

VLow2

VLow2 Flag is set when supply voltage drops below VLow2 threshold

•

Indicating a risk that the 32.768 kHz might have stopped due to low supply voltage and that the time & date

information might be corrupted

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