The ADM803/ADM809/ADM810 supervisory circuits monitor the power supply voltage in microprocessor systems. They provide a reset output during power-up， power-down， and brownout conditions. On power-up， an internal timer holds reset asserted for 240 ms. This holds the microprocessor in a reset state until conditions have stabilized. The reset output remains operational with VCC as low as 1 V. The ADM803 and ADM809 provide an active low reset signal （RESET）， whereas the ADM810 provides an active high signal （RESET） output. The ADM809 and ADM810 have push-pull outputs， whereas the ADM803 has an open-drain output， which requires an external pull-up resistor. Seven reset threshold voltage options are available， suitable for monitoring a variety of supply voltages （see Table 3）。 The reset comparator features built-in glitch immunity， making it immune to fast transients on VCC. The ADM803/ADM809/ADM810 consume only 17 μA， making them suitable for low power， portable equipment. The ADM803 is available in a 3-lead SC70; the ADM809/ADM810 are available in 3-lead SOT-23 and 3-lead SC70 packages.