From Manuvr Breakouts on Tindie:
The MCP3564 is a 24-bit sigma-delta ADC with support for up to eight single-ended, or four differential channels. It supports extensive oversampling depths, flexible MUX front-end, circuit burnout detection, adjustable gain, Vref from [0v – 3.6v], and optional internal oscillator.
The board is available with or without high-accuracy external oscillator. If included, the oscillator frequency is fixed at the maximum rate for this part (19.6608 MHz).