Microcontrollers Pack "Zooming" A/D Converter

In addition to the hardware needed to directly interface piezoresistive sensors, XE88LCxx microcontrollers also contain circuitry that enables small signals with large offsets to be measured at maximum resolutions. This is made possible by a "zooming" A/D converter that resides in the controllers' data acquisition block. Called the ZoomingADC, the novel A/D converter amplifies the input signal before converting it to a 16-bit code. The user selects that part of the signal having the desired data, zooms in on it, and applies the full resolution of the ADC to it. By sharing the gain and offset compensation over three stages, the ZoomingADC can compensate for large offsets on a small signal without saturation or resolution losses. A differential path allows the converter to capture both single and differential signals.
The CPU controls the data acquisition process and computes any necessary linearization. Signal output is made through the UART, parallel port, or one of the DACs. The new, ultra-low power (300 µA at 1 MIPS) MCU can operate from a 1.2V to 5.5V supply and includes a watchdog timer, RC and crystal oscillators, and more. The XE88LCxx µC family comes in several flavors, with XE88LC01 costing $8 each/10K.