The recommended power-up sequence is to apply VCC first, followed by VBAT. This ensures that the internal circuitry is properly initialized and that the device starts up in a known state.
To ensure reliable startup of the oscillator, make sure that the crystal is properly connected and that the load capacitors are correctly sized. Also, ensure that the power supply is stable and that there are no noise sources that could interfere with the oscillator startup.
The maximum allowed voltage on the VBAT pin is 3.6V. Exceeding this voltage can cause damage to the device.
When the battery is removed or replaced, the DS1283SN will reset and the clock will be lost. To handle this case, you can use the device's power-fail detect feature to detect when the battery is removed and take appropriate action, such as saving the clock data to non-volatile memory.
The internal oscillator of the DS1283SN has an accuracy of ±10 ppm over the operating temperature range of -40°C to +85°C.
DS1283SN datasheet
by Maxim Integrated Products
