This work is concerned with the design and the characterization of front-end channels, developed in a 28 nm CMOS technology, conceived for the readout of pixel sensors in future, high-rate applications at the next generation facilities. Two front-end architectures are discussed. In the first one, an in-pixel flash ADC is exploited for the digitization of the signal, whereas the second one features a Time-over-Threshold (ToT) approach. A prototype including the ADC-based front-end has been submitted and the characterization of the chip is discussed in the paper. Simulation results relevant to the ToT-based architecture are reported.