电源电压监事 SUPPLY-VOLTAGE SUPERVISORS
Description
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 RESEToutput becomes active low when VCCattains 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 RESETand RESET go inactive high and low, respectively. When an undervoltage condition occurs during normal operation, RESETand 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 CTis in farads F and tdis in seconds s.
During power down and when SENSE is below VIT–, the outputs remain active until VCCfalls 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