characteristic
 Can measure seconds, minutes, hours, days of the week, days, months and years based on 32.768kHz crystal
 With century mark
Wide operating voltage range: 1.5～5.5V
 Low sleep current: typical value is 0.25μA (VDD=3.0V, TA=25℃)
 I2C bus slave address: read, 0A3H; write, 0A2H
 Programmable clock output frequency: 32.768kHz, 1024Hz, 32Hz, 1Hz
 Alarm and timer
 Power-off detector
 Internally integrated oscillation capacitor
 Packaging form: SOP8/MSOP8/TSSOP8
 Open-drain interrupt pin