The TL77xxA family of integrated-circuit supply-voltage supervisors is designed specifically for use as reset controllers in microcomputer and microprocessor systems. The supply-voltage supervisor monitors the supply for undervoltage conditions at the SENSE input. During power up, the RESET output becomes active (low) when VCC attains a value approaching 3.6 V. At this point (assuming that SENSE is above VIT+), the delay timer function activates a time delay, after which outputs RESET and RESET go inactive (high and low, respectively). When an undervoltage condition occurs during normal operation, RESET and RESET go active. To ensure that a complete reset occurs, the reset outputs remain active for a time delay after the voltage at the SENSE input exceeds the positive-going threshold value. The time delay is determined by the value of the external capacitor CT: td = 1.3 × 104 × CT, where CT is in farads (F) and td is in seconds (s).
During power down and when SENSE is below VIT−, the outputs remain active until VCC falls below 2 V. After this, the outputs are undefined.
An external capacitor (typically 0.1 µF) must be connected to REF to reduce the influence of fast transients in the supply voltage.
● Power-On Reset Generator
● Automatic Reset Generation After Voltage Drop
● Wide Supply-Voltage Range
● Precision Voltage Sensor
● Temperature-Compensated Voltage Reference
● True and Complement Reset Outputs
● Externally Adjustable Pulse Duration