The Concentrator Integrated Circuit (CIC) ASIC is a front-end chip for both Pixel-Strip (PS) and Strip-Strip (2S) modules of the future Phase 2 CMS Outer Tracker at the High-Luminosity LHC (HL-LHC). Prototyped in a 65 nm CMOS technology, the CIC aggregates the digital data coming from eight upstream front-end chips, formatting it into data packets containing the trigger information from eight bunch crossings and the raw data from events passing the Level 1 (L1) trigger, before transmission to the lpGBT. The role of the CIC in the readout chain is to provide an extra factor of data reduction by grouping data over time and space. A first prototype, the CIC1, integrating all functionalities for system level operation, has been tested in early 2019. A brief description of the functionalities and the test results obtained concerning the performance characterization and the radiation tolerance of the chip are presented in this contribution.