Maxim > App Notes > MICROPROCESSOR SUPERVISOR CIRCUITS

 

Keywords: sequencing, sequencer, monitor, reset, voltage tracking, voltage tracker

Sep 20, 2006

APPLICATION NOTE 3918

User's Guide for the MAX6877 Power-Supply Tracker/Sequencer

Abstract: This application note is a step-by-step User's Guide for designing with the MAX6877 voltage tracker and sequencer. The note explains how to make suitable component calculations.

Figure 1. The basic circuit for the MAX6877.

MAX6877 Overview

Tracks or sequences up to three voltages

Closed-loop tracking control with programmable slew rate

Program thresholds with resistors

Program slew rate and timing delays with capacitors

Fault output and power-good output

Description

The MAX6877 voltage tracker/sequencer can track or sequence up to three voltages. Use the TRACK/SEQ pin to select tracking or sequencing. The device will either track or sequence the three voltages, but it cannot track and sequence simultaneously. Power-up begins when EN/active-low UV is asserted and all three input voltages are above their thresholds. In the example circuit in Figure 1, EN/active-low UV is connected to the 12V bus, so the circuit will turn on when the bus exceeds its threshold and turn off when it falls under its threshold.

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Maxim manual Users Guide for the MAX6877 Power-Supply Tracker/Sequencer, MAX6877 Overview, Description

MAX6877 specifications

The Maxim MAX6877 is a highly efficient voltage supervisor designed for a wide range of applications, ensuring reliable operation and protection for sensitive electronic devices. This device is particularly well-suited for applications where monitoring power supply voltages is critical, such as in power management systems, consumer electronics, and industrial automation.

One of the key features of the MAX6877 is its low voltage operation, which enables it to monitor supply voltages as low as 0.5V. This makes it ideal for applications utilizing low voltage power supplies, especially in battery-operated devices where efficient energy usage is paramount. The MAX6877 also boasts a precise voltage detection capability with an accuracy of ±2%, ensuring consistent and reliable operation.

A standout characteristic of the MAX6877 is its adjustable reset threshold. Users can tailor the reset voltage to specific requirements using external resistor dividers, providing flexible solutions for various applications. Additionally, the device incorporates a power-on reset function that ensures the system starts only when the supply voltage stabilizes, safeguarding against erratic behavior during power-up conditions.

The MAX6877 employs a watchdog timer feature, which is essential for monitoring the health of a microcontroller or processor. This feature can reset the system if the microcontroller becomes unresponsive, thereby enhancing system reliability and uptime. The watchdog is configurable, allowing designers to set the timeout period according to application needs.

Another impressive aspect of the MAX6877 is its compact design, available in a small SOT-23 package, ensuring minimal footprint on the printed circuit board. This is particularly beneficial in space-constrained designs, such as handheld devices or embedded systems.

The device operates over a wide temperature range, from -40°C to +125°C, making it suitable for both industrial and automotive applications. Additionally, the MAX6877 draws minimal quiescent current, which is advantageous in battery-powered devices, prolonging battery life and improving efficiency.

In summary, the Maxim MAX6877 is a versatile and reliable voltage supervisor, characterized by its low voltage operation, adjustable reset threshold, watchdog timer feature, and compact design. With its robust performance and energy-efficient capabilities, the MAX6877 is an excellent choice for a variety of applications requiring precise voltage management and system reliability.