LM3722IM5X-4.63 Electronic IC Chips 5-Pin Microprocessor Reset Circuits

LM3722/LM3723/LM3724

5-Pin Microprocessor Reset Circuits

General 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 V_CC 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.

Features

• Precise monitoring of 2.5V, 3.3V, and 5V supply voltages

• Fully specified over temperature

    Industrial: −40˚C to +85˚C

    Extended: −40˚C to +125˚C

• 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)

• Guaranteed RESET Output valid for V_CC ≥ 1V

• Low Supply Current, 6µA typical

• Power supply transient immunity

• Compatible with MAX811/812 applications

Applications

• Microprocessor Systems

• Computers

• Controllers

• Intelligent Instruments

• Portable/Battery-Powered Equipment

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

V_CC, MR                                                                       −0.3V to 6.0V

RESET, RESET                                                −0.3V to (V_CC+ 0.3V)

Input Current, V_CC Pin                                                              20mA

Output Current, RESET, RESET Pin                                         20mA

ESD Rating (Note 2)                                                                    2kV

Continuous Power Dissipation (T_A = +70˚C)

    SOT-23 (Note 3)                                                                320mW

Operating Temperature Range

    Industrial:                                                               −40˚C to +85˚C

    Extended:                                                             −40˚C to +125˚C

Maximum Junction Temperature                                               125˚C

Storage Temperature Range                                   −65˚C to +160˚C

Lead Temperature (soldering, 10sec)                                    +300˚C

Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which the device operates correctly. Operating ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics.

Note 2: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin.

Note 3: At elevated temperatures, devices must be derated based on package thermal resistance. The device in the SOT23-5 package must be derated at 4.5mW/˚C at ambient temperatures above 70˚C. The device has internal thermal protection.

Typical Application Circuit

Connection Diagram

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