Analog Devices Inc./Maxim Integrated MAX809SEUR+T

Digital system power supply voltage monitoring is the purpose of the microprocessor (µP) supervisory circuit MAX809SEUR-T. By producing a reset signal during power-up, power-down, and brown-out scenarios, it serves as the main means of guaranteeing the stability and correct operation of µPs. This chip is widely used in embedded systems, automotive control systems, and consumer electronics.

The capacity to monitor standard supply voltages (usually 3V, 3.3V, and 5V), excellent accuracy in reset threshold settings, and low power consumption, which makes the MAX809SEUR-T ideally suited for battery-powered applications, are some of its noteworthy advantages.

Application in Embedded Systems:

In an embedded system, the MAX809SEUR-T is crucial for maintaining system reliability, particularly in scenarios with fluctuating power supplies.

Detailed Circuit Connection Description:

1. Power Supply Monitoring: The VCC pin (Pin 1) of the MAX809SEUR-T should be connected to the power supply of the embedded system. This enables the MAX809SEUR-T to continuously monitor the system's voltage level.

2. Ground Connection: The GND pin (Pin 2) of the MAX809SEUR-T must be connected to the system's ground. This connection provides a reference point for the voltage monitoring function.

3. Reset Signal Implementation: The RESET pin (Pin 3) of the MAX809SEUR-T is connected to the µP's reset input. This ensures the generation of a reset signal when the voltage falls below a safe operating threshold.

4. Reset Timing Adjustment: Optionally, connecting a capacitor between the RESET pin and ground allows for customization of the reset signal's timing, offering flexibility in the system's response to power fluctuations.

Key Circuit Design Considerations:

1. Selecting the Right Voltage Threshold: Choosing a MAX809SEUR-T variant with a voltage threshold matching the embedded system's operating voltage is crucial for accurate and effective monitoring.

2. Addressing Voltage Fluctuations: Placing filtering capacitors near the MAX809SEUR-T's power input is advisable to protect against voltage spikes that could inadvertently trigger a reset.

3. Compatibility with µP Reset Input: The reset output from the MAX809SEUR-T must be compatible with the µP's reset input requirements, including voltage level and pulse duration.

4. Environmental Factors: Consideration of the operating environment, such as temperature and humidity, is important as they can affect the MAX809SEUR-T's performance.

5. Power Source Consistency: For battery-operated embedded systems, ensuring that the battery voltage remains within the functional range of the MAX809SEUR-T is vital for consistent voltage monitoring.

Integrating the MAX809SEUR-T into embedded systems involves a thorough understanding of the system's power requirements, environmental conditions, and compatibility factors. Its role in monitoring the power supply and ensuring system stability is crucial, especially in sophisticated and sensitive electronic applications.

The MAX809SEUR+T is a microprocessor (µP) supervisory circuit, commonly used for monitoring the power supply voltage in digital systems. It is designed to assert a reset signal to the µP whenever the monitored power supply voltage falls below a preset threshold, ensuring proper system startup and preventing system failures due to low voltage. Key features of the MAX809SEUR+T include a precise voltage monitor, low power consumption, and a small SOT23 package.

Application in Microcontroller-Based Systems:

A typical application of the MAX809SEUR+T is in a microcontroller-based system, where it ensures the microcontroller resets correctly during power-up, power-down, and brown-out conditions.

1. Power Supply Connection: The VCC pin (pin 1) of the MAX809SEUR+T is connected to the system's power supply, typically 5V. This connection allows the MAX809SEUR+T to monitor the power supply voltage.

2. Reset Output to Microcontroller: The RESET pin (pin 2) of the MAX809SEUR+T is connected to the reset input of the microcontroller. When the supply voltage drops below the threshold, the MAX809SEUR+T drives this pin low, resetting the microcontroller.

3. Grounding: The GND pin (pin 3) of the MAX809SEUR+T is connected to the system's ground. This provides a reference for the supply voltage monitoring.

4. Bypass Capacitor Placement: A bypass capacitor (typically 0.1 µF) should be placed close to the VCC pin of the MAX809SEUR+T to stabilize the power supply line and filter out noise.

Key Circuit Design Considerations:

When integrating the MAX809SEUR+T into a circuit, several important factors must be considered:

1. Stable Power Supply: Ensuring a clean and stable power supply for the MAX809SEUR+T is crucial for accurate voltage monitoring.

2. Correct Reset Threshold Selection: Choosing a MAX809SEUR+T variant with an appropriate reset threshold voltage for the system's power supply voltage is essential.

3. Minimizing Noise on the Reset Line: Layout considerations to minimize noise on the reset line are important to prevent false triggering of the reset function.

4. Timing Capacitor for Reset Delay (if required): In some applications, adding a capacitor to the RESET pin can be used to adjust the reset signal timing to meet specific system requirements.

In conclusion, the MAX809SEUR+T is highly suitable for microcontroller-based systems, offering reliable power supply monitoring and reset control. Key considerations in such designs include a stable power supply, correct threshold voltage selection, noise minimization on the reset line, and optional timing adjustments, ensuring the effective operation of the MAX809SEUR+T in maintaining system stability.