Sar adc with dynamic input scaling and offset adjustment

An apparatus for generating an image of touch on or about a touch-sensitive surface, comprising:

• a touch panel, the touch panel including a plurality of touch sensors configured for detecting one or more touch events;
• and
• a plurality of receive channels couplable to the touch panel for generating values representative of detected touch events, at least some of the plurality of receive channels comprising:
• (i) a charge amplifier connectable to the multi-touch panel;
• (ii) an anti-aliasing filter connectable to the charge amplifier;
• and
• (iii) a successive approximation register digital-to-analog converter (SAR ADC) connectable to the anti-aliasing filter, the SAR ADC configurable to convert an analog waveform into a digital representation using a binary search and outputting the digital representation to an output register.

A multi-touch subsystem for detecting touch events on or about a touch-sensitive surface and generating an image of touch, comprising:

• driver logic configured for generating an input stimulus;
• channel scan logic configured for controlling the driver logic to sequentially scan each row of touch sensors in a touch panel, and to sequentially scan each row of proximity sensors in a proximity sensor panel, by sequentially driving each row with the input stimulus;
• and
• one or more receive channels, each receive channel couplable to a column of touch sensors in the touch panel or a column of proximity sensors in the proximity sensor panel, each receive channel comprising a charge redistribution SAR ADC configured for receiving a signal representative of a touch event occurring at one of the touch sensors in the column of touch sensors and generating a digital value representative of the touch event via a binary search,
• wherein scanning one or more rows in the touch panel enables a detection of multiple touch events occurring at distinct locations at about the same time.

A method for detecting touch events on or about a touch-sensitive surface, comprising:

• scanning a touch panel of touch sensors organized in rows and columns by sequentially applying a first stimulus to each row;
• and
• during each touch panel row scan, coupling the columns of the touch panel to one or more receive channels and generating one or more digital values representative of one or more touch events occurring at distinct locations along the row at about the same time,
• wherein generating the one or more digital values comprises converting an analog waveform into a digital representation via a binary search implemented by a charge redistribution SAR ADC.