The VMM3a is a custom Application-Specific Integrated Circuit. It will be used as the front-end chip for both Micromegas and sTGC detectors of the ATLAS Muon New Small Wheel upgrade at CERN. Due to its flexibility and several configurable parameters, it has also been proposed for a variety of tracking detectors in other experiments. The VMM integrates 64 independent channels, each providing amplitude and timing measurements in digital or analog format. The chip has undergone three major revisions and a minor one, with the first prototype being produced in 2012. It began as a purely analog chip, providing timing and amplitude measurements for digitization by external analog-to-digital converters, while its latest version combines analog circuitry, embedded digitizers, buffers, radiation-protection logic and modules that produce fast signals for triggering, all in one chip - the VMM3a. In this document, the design aspects of the VMM3a as a production front-end chip will be presented.