A delta sigma analog-to-digital converter (ADC) providing optimized performance and energy consumption. In one embodiment, a delta-sigma ADC includes a loop filter and a multi-bit quantizer. The multi-bit quantizer is coupled to the loop filter. The quantizer includes a counter, a reference voltage generator, and a comparator. The counter is configured to provide a multi-bit output value that estimates an output of the loop filter. The reference voltage generator is configured to generate a reference voltage ramp based on the output value of the counter. The comparator is coupled to the reference voltage generator to compare the reference voltage ramp to output of the loop filter.