At the end of the electrical characteristics table in the datasheet (Rev 7 11/16), it is stated in note 6 that the IC enters shutdown mode after SCL < VIL and SDA < VIL for longer than 2.5s. However, there is no specific description of the shutdown mode.
Based on the fact that note 6 applies to Bus Low-Detection Timeout (tSLEEP) in the electrical characteristics table, and from the description of the "Sleep Mode" on page 10 of the datasheet (Rev 7 11/16),
"To enter sleep mode, write MODE.EnSleep = 1 and either:
• Hold SDA and SCL logic-low for a period for tSLEEP. A rising edge on SDA or SCL wakes up the IC", the datasheet actually refers shutdown mode as "SLEEP."
In sleep mode, the IC halts all operations, reducing current consumption to below 1µA. IC does not detect self-discharge in sleep mode. After exiting sleep mode, it will continue normal operation.