## Overview of the MAX809-R The **MAX809-R** is a compact, low-power microprocessor ($\mu$P) supervisory circuit. Its primary function is to monitor the power supply voltage in digital systems and provide a **Reset** signal to the processor when the voltage falls below a specific threshold. ### Key Specifications and Functions | Feature | Specification / Description | | :--- | :--- | | **Reset Threshold** | 2.63V (indicated by the 'R' suffix) | | **Reset Type** | Push-Pull, Active-Low | | **Supply Voltage Range** | 1.0V to 5.5V | | **Supply Current** | Typically 6µA (Very Low Power) | | **Reset Timeout Period** | Minimum 140ms (Typically 240ms) | | **Package Type** | Commonly SOT-23 or SC-70 | --- ### Internal Functional Blocks The MAX809-R contains several critical electronic components integrated into a single silicon chip: 1. **Precision Voltage Reference:** A stable internal reference (usually a Bandgap reference) used to compare the incoming $V_{CC}$ against the set threshold. 2. **Voltage Comparator:** Compares $V_{CC}$ with the internal reference. It includes built-in hysteresis to prevent "chattering" (rapid switching) if the power supply is noisy. 3. **Timing Generator (Delay):** Once $V_{CC}$ rises above the threshold, this block keeps the Reset signal active for at least 140ms to allow the power supply and the system clock to stabilize. 4. **Push-Pull Output Stage:** Unlike "Open-Drain" outputs, a Push-Pull stage does not require an external pull-up resistor. It can actively drive the line High or Low. --- ### Typical Application Circuit The MAX809-R is designed for simplicity. Below is a representation of how it is typically wired to a Microcontroller (MCU). ```mermaid graph LR VCC((VCC 3.0V)) --> MAX[MAX809-R] MAX --> GND((GND)) MAX -- RESET Line --> MCU[Microcontroller RESET Pin] ``` ### Pin Configuration (SOT-23) | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | **GND** | Ground reference. | | 2 | **RESET** | Output signal. Stays LOW when $V_{CC}$ is below 2.63V and for 140ms after $V_{CC}$ rises above 2.63V. | | 3 | **Vcc** | Supply voltage input and monitored voltage. | --- ### Why use the "R" Version? The "R" suffix specifically denotes a **2.63V threshold**. This is ideal for **3.0V or 3.3V systems**. It ensures that if a 3.3V rail drops significantly (entering a "brownout" state), the microcontroller is forced into reset before it begins to execute instructions incorrectly or corrupts memory.