1. An apparatus comprising: a first track and hold stage configured to track and store an input voltage for a sample of an analog input signal; a coarse reference ladder providing a plurality of coarse references; a coarse analog-to-digital converter (ADC) configured to receive the input voltage from the first track and hold stage and the plurality of coarse references, the coarse ADC configured to perform a first comparison of the input voltage and the plurality of coarse references and output a coarse output based on the first comparison; a switch matrix including a plurality of switches, the switch matrix configured to close a switch based on the coarse output, the switch corresponding to a coarse reference; a second track and hold stage configured to track and store the input voltage; a fine reference ladder configured to receive the coarse reference and provide a plurality of fine references determined based on the coarse reference; a fine ADC configured to receive the input voltage from the second track and hold stage and the plurality of fine references, wherein the fine ADC is configured perform a second comparison of the input voltage and the plurality of fine references and output a fine output based on the second comparison; and logic configured to output a digital output for the sample of the analog input signal based on the coarse output and the fine output.