onsemi CAT811RTBI: Pinout, Datasheet, and Application Circuit Guide

In the realm of embedded systems and digital electronics, ensuring a stable and reliable power supply is paramount. The onsemi CAT811RTBI stands as a critical component in this effort, a high-performance microprocessor (µP) supervisory circuit designed to monitor power supplies and protect sensitive systems. This guide delves into its pinout, key datasheet specifications, and a typical application circuit to empower your design process.

Pinout Configuration

The CAT811RTBI is available in the space-efficient SOT-23-5 package. Understanding the function of each pin is the first step to effective implementation.

1. GND (Pin 1): Ground connection. This is the common reference point for the entire IC.

2. MR (Manual Reset Input, Pin 2): An active-low, Schmitt-trigger input that allows an external switch or logic circuit to force a reset. This pin can be left floating if not used but is typically pulled high to VCC via a resistor.

3. VCC (Power Supply, Pin 3): The positive power supply pin. This pin is connected to the system's power rail that requires monitoring.

4. RST (Reset Output, Pin 4): An active-low, open-drain output. This pin asserts a low signal whenever the VCC supply drops below the factory-set threshold voltage, providing a reset command to the µP.

5. NC (Pin 5): No Internal Connection. This pin is electrically isolated and can be left floating or connected to ground.

Key Datasheet Specifications

The CAT811RTBI is engineered for precision and robustness. Key specifications from its datasheet include:

Reset Threshold Voltage: The CAT811RTBI is offered in standard threshold options (e.g., 2.93V, 3.08V, 4.38V, 4.63V). This specific part's suffix denotes its precise voltage.

Active-Low Open-Drain Reset Output (RST): Requires an external pull-up resistor (typically 10kΩ to 100kΩ) to the µP's logic supply voltage. This allows for flexibility when interfacing with µP logic levels that may differ from the monitored VCC.

Manual Reset Input (MR): Provides a debounced input for initiating a processor reset via a push-button switch.

Low Supply Current: Typically consumes only 40µA, making it suitable for power-sensitive, battery-operated applications.

Operating Range: The device functions with a wide VCC range, typically from 1.0V to 5.5V.

Typical Application Circuit

A standard application circuit for the CAT811RTBI is straightforward to implement, making it a favorite among designers.

Components Required:

IC1: CAT811RTBI (with desired threshold voltage, e.g., 3.08V for a 3.3V system)

R1: 10kΩ Pull-up Resistor (for RST output)

R2: 10kΩ Pull-up Resistor (for MR input)

S1: Normally-open Tactile Switch (for manual reset)

C1: 0.1µF Bypass/Decoupling Capacitor (placed close to the VCC and GND pins)

Circuit Operation:

1. Power-On Reset: When power is applied and VCC rises, the RST pin remains asserted (low) until VCC exceeds the reset threshold voltage. After a brief timeout period (typically 140ms to 280ms), the RST pin is released (pulled high by R1), allowing the microprocessor to begin operation.

2. Brown-Out Protection: If the supply voltage VCC drops below the specified threshold during operation, the RST pin immediately asserts low, halting the µP and preventing code execution errors or data corruption.

3. Manual Reset: Pressing the switch S1 pulls the MR pin to ground, which immediately forces the RST output low, initiating a system reset regardless of the supply voltage condition.

This circuit ensures your microcontroller starts in a known state and remains protected from unpredictable power-related faults.

ICGOODFIND: The onsemi CAT811RTBI is an indispensable, robust, and cost-effective solution for microprocessor power supervision. Its simple integration, low power consumption, and reliable performance in monitoring power supply integrity make it an excellent choice for a vast array of applications, from consumer electronics to industrial control systems.

Keywords: Power Supervision, Manual Reset, Brown-Out Protection, Microprocessor Supervisor, Open-Drain Output.