A pressure sensor device is to be positioned within a material where a mechanical parameter is measured. The pressure sensor device may include an IC having a ring oscillator with an inverter stage having first doped and second doped piezoresistor couples. Each piezoresistor couple may include two piezoresistors arranged orthogonal to one another with a same resistance value. Each piezoresistor couple may have first and second resistance values responsive to pressure. The IC may include an output interface coupled to the ring oscillator and configured to generate a pressure output signal based upon the first and second resistance values and indicative of pressure normal to the IC.