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.
The LM3722, LM3723 and LM3724 are microprocessor supervisory circuits that monitor power supplies and provide a reset signal during power‑up, power‑down, brown‑out and manual reset conditions. They are offered in a 5‑pin SOT‑23 package with low supply current and selectable reset voltage thresholds for 5 V, 3.3 V and 2.5 V systems.
The document includes detailed electrical characteristics, timing diagrams, pin descriptions, ordering information and physical dimensions, as well as application notes for portable and battery‑powered equipment.
| Reset voltage options | 4.63 V, 3.08 V, 2.32 V |
|---|---|
| Supply current | 6 µA typical |
| Package | 5‑pin SOT‑23 |
| Operating temperature range (Industrial) | -40 °C to +85 °C |
| Operating temperature range (Extended) | -40 °C to +125 °C |
| Reset timeout (typical) | 190 ms |
| RESET output valid for | VEG = 1 V |
The LM3722 provides an active‑low push‑pull RESET output.
The devices have a low supply current of about 6 µA typical.
They operate from –40 °C to +85 °C in the industrial temperature range.
The reset signal remains asserted for 190 ms after VCC rises above the threshold.