AR1021 - What type of ratiometric conversion do Microchip touch controllers use?

Microchip has not made any ratiometric claims with the AR1011 or AR1021. Alternatively, all TSHARC controllers are ratiometric through hardware. The TSHARC controllers use the drive lines as references for the ADC which makes them ratiometric. TSHARC controllers are also more expensive: HSA2-040SIA/A2S23.

The ratiometric conversion keeps the touchscreen from drifting as the resistance of the ITO, tail, or both drift with temperature over time. If a four-wire or five-wire touch-screen tail and ITO drift differently, they are not truly ratiometric. Eight-wire touchscreens are built to address just this problem. TSHARC controllers connected and configured for eight-wire are the only true ratiometric controllers.

The Microchip mTouch® technology ARxxxx Series Resistive Touch Screen Controllers are not recommended for new designs. Visit microchip.com/touch for our latest products.

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