For microcontrollers without an analog-to-digital converter or when you want a higher-precision ADC, the ADS1115 provides 16-bit precision at 860 samples/second over I2C. The chip can be configured as 4 single-ended input channels, or two differential channels.
Description: Ultra-Small, Low-Power, 16-Bit Analog-to-Digital Converter with Internal Reference. Manufacturer: Texas Instruments.
The ADS1115 is a precise 16bit ADC with four multiplexed inputs - You can use each input on its own, or in pairs for differential measurements. It has an internal calibrated reference for high accuracy.