Low-power semiconductor voltage comparator with hysteresis

摘要

The low power voltage comparator with hysteresis includes a comparator (10) that is operable to receive the output from a battery (14) on the positive input thereof and the output of a battery (16) on the negative input thereof. An offset circuit (22) is provided in series with the voltage of the battery (14) and the comparator (10), and an offset circuit (24) is provided between the battery (16) and the comparator (10). The offset circuits (22) and (24) are adjustable by a hysteresis control circuit (26) to offset the voltage thereof for the non-selected battery to be higher than that for the selected battery such that the voltage drop across the offset for the non-selected battery is greater than that for the selected battery. When the voltage on the selected battery falls below the offset voltage of the non-selected battery, the hysteresis control then decreases the offset upon selecting the other battery and increases the offset or the battery that is deselected. The offset circuits (22) and (24) each comprise primary resistive elements (26) and (36) which are connected through a current sink (50) to ground. The selection process by the hysteresis control circuit (26) is operable to place a parallel resistor (32) or (44) in parallel with the resistors (26) and (36), respectively. The selection process is effected with switches (34) and (46).