MAX31328 I2C Real-Time Clock (RTC) Analog Devices Inc. MAX31328 I2C Real-Time Clock (RTC) is a low-cost, extremely accurate time-keeping device featuring an integrated temperature-compensated 32kHz crystal oscillator (TCXO) and crystal. The device incorporates a battery input and maintains accurate timekeeping when the main power to the device is interrupted. The integration of the crystal resonator enhances the long-term accuracy of the device and eliminates the external crystal requirement in the system.