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5-Pin Microprocessor Reset Circuits


Description:

The LM3722/LM3723/LM3724 microprocessor supervisory circuits monitor the power supplies in microprocessor and digital systems. They provide a reset to the microprocessor during power-up, power-down, brown-out conditions, and manual reset.
The LM3722/LM3723/LM3724 asserts a reset signal whenever the supply decreases below the factory-programmed reset threshold for at least 100 ms. The reset signal remains asserted for 190 ms after VCC rises above the threshold.
The LM3722 has an active-low RESET push-pull output. The LM3723 has an active-high RESET push-pull output. The LM3724 has an active-low open-drain RESET output. Three standard reset voltage options are available, suitable for monitoring 5V, 3.3V, and 2.5V supply voltages. Additional reset voltages are also available; contact National Semiconductor for details.
With a low supply current of only 6µA, the LM3722/LM3723/LM3724 are ideal for use in portable equipment. The LM3722/LM3723/LM3724 are available in the 5-pin SOT23 package.


Applications:

n Precise monitoring of 2.5V, 3.3V, and 5V supply voltages
n Fully specified over temperature Industrial: −40˚C to +85˚C
Extended: −40˚C to +125˚C
n 100 ms minimum Power-On Reset pulse width, 190 ms typical:
Active-Low RESET Output (LM3722)
Active-High RESET Output (LM3723)
Active-Low RESET Open Drain Output (LM3724)
n Guaranteed RESET Output valid for VCC ≥ 1V
n Low Supply Current, 6µA typical
n Power supply transient immunity
n Compatible with MAX811/812 applications


Specifications: