DESCRIPTION
During power-up the device tests the supply voltage and keeps the RESET and RESET outputs active (high and low, respectively) as long as the supply voltage has not reached its nominal voltage value. Taking RESIN low has the same effect. To ensure that the microcomputer system hasreset, the TL7700Athen initiates aninternal time delay that delays the return of the reset outputs to theirinactivestates. Since the timedelay for most microcomputersand microprocessors is in the order of several machine cycles, the device internal time delay is determined by an external time delay is determined by an external capacitor connected to the CT input (pin 3). td = 1.3 x 104 x CT Where : CT is in farads (F) and td in seconds (s). In addition, when the supply voltage drops below the nominal value, the outputs will be active until the supply voltage returns to the nominal value. An externalcapacitor(typically0.1 µF) must be connected to the REF output (pin 1) to reduce the influence of fast transients in the supply voltage.
STMicroelectronics
