Abstract: An integrated circuit voltage converter containing a capacitive charge pump performing DC to DC conversion is disclosed which detects, either automatically or by an external signal, the onset of a low power consumption situation and switches to a low power consumption mode. In one embodiment, the low power consumption mode is accomplished by reducing the operating frequency of the charge pump. In another embodiment, the switching transistors used to switch the capacitors in the charge pump during a low power consumption mode are smaller than those transistors used to switch the capacitors during its normal operating mode. In another embodiment, the DC to DC converter switches back and forth between a high frequency (burst) mode and a low frequency (low power) mode at intervals. In another embodiment, a combination of the power reduction techniques is used. Various techniques for detecting when a low power consumption mode is appropriate are also described.

Abstract: A successive approximation analog-to-digital converter utilizes an improved high-gain current comparator having a zero input impedance characteristic in combination with an equal current digital-to-analog converter. The zero input impedance comparator permits the use of low power C-MOS switching circuitry by leading the output of the digital-to-analog converter to the zero impedance input of the comparator, thereby overcoming the problem of decreased switching speed associated with high capacitance C-MOS outputs. The zero impedance current comparator includes an improved current-to-voltage converter having an overdrive shunt circuit to reduce quiescent current and to permit higher value load resistors for better gain; and cascaded current cells to provide increased gain.