SBAA565 November 2022 ADC081C021 , ADC081C027 , ADC101C021 , ADC101C027 , ADC121C021 , ADC121C021-Q1 , ADC121C027 , ADC128D818 , ADS1000 , ADS1000-Q1 , ADS1013 , ADS1014 , ADS1015 , ADS1015-Q1 , ADS1100 , ADS1110 , ADS1112 , ADS1113 , ADS1114 , ADS1115 , ADS1115-Q1 , ADS7823 , ADS7827 , ADS7828 , ADS7828-Q1 , ADS7830 , ADS7924 , AFE539A4 , DAC081C081 , DAC081C085 , DAC101C081 , DAC101C081Q , DAC101C085 , DAC121C081 , DAC121C085 , DAC43204 , DAC43401 , DAC43401-Q1 , DAC43608 , DAC43701 , DAC43701-Q1 , DAC53002 , DAC53004 , DAC53202 , DAC53204 , DAC53204W , DAC53401 , DAC53401-Q1 , DAC53608 , DAC53701 , DAC53701-Q1 , DAC5571 , DAC5573 , DAC5574 , DAC5578 , DAC60501 , DAC60502 , DAC63002 , DAC63004 , DAC63202 , DAC63204 , DAC6571 , DAC6573 , DAC6574 , DAC6578 , DAC70501 , DAC70502 , DAC7571 , DAC7573 , DAC7574 , DAC7578 , DAC7678 , DAC80501 , DAC80502 , DAC8571 , DAC8574
In Figure 6-10, the controller and pullups are set to 5 V, but the target device is set to 3.3 V.
The I2C bus lines are able to be pulled up to 5 V, exceeding the target device supply. However, the target device has inputs tolerant to higher voltages. This higher tolerance is a feature in some I2C devices. This feature allows for direct connections between the I2C bus with pullups to the higher voltage supply. Check with the device data sheets for this possible feature.
As an example, the ADS1115 is just one device that has SDA and SCL lines that are tolerant to voltages higher than the supply. Looking at the Absolute Maximum Table from the data sheet, the maximum digital input voltage is 5.5 V, regardless of the supply voltage. With this type of I2C line, the target device can tolerate pullup voltages higher than the supply. This allows for I2C communication between the devices even with different supply voltages.