## Overview of the ADM823SYRJZ-R7 The **ADM823SYRJZ-R7** is a precision supervisory circuit manufactured by **Analog Devices**. It is designed to monitor power supply voltage levels and code execution integrity in microprocessor-based systems. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Function** | Microprocessor Supervisory Circuit | | **Threshold Voltage ($V_{TH}$)** | 2.93V (Typical) | | **Supply Voltage Range** | 1.0V to 5.5V | | **Reset Timeout Period** | 140 ms (Minimum) | | **Watchdog Timeout** | 1.6 sec (Typical) | | **Output Type** | Push-Pull, Active-Low Reset | | **Package / Case** | SOT-23-5 | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Core Functional Blocks This component integrates several critical safety functions into a single small-footprint package: * **Voltage Monitor:** It continuously checks the $V_{CC}$ input. If the voltage falls below the preset threshold (2.93V for the 'S' variant), the device asserts a RESET signal to prevent the processor from operating under unstable power conditions. * **Watchdog Timer (WDI):** This feature ensures software integrity. The microprocessor must "pet" or toggle the WDI pin within a specific window (1.6 seconds). If the software freezes and fails to toggle the pin, the ADM823 triggers a hardware reset. * **Manual Reset (MR) Input:** Allows for an external push-button or logic signal to force a system reset independently of the voltage or watchdog status. * **Power-On Reset (POR):** Ensures that the microprocessor starts in a known state by holding the reset line active for at least 140ms after power reaches the threshold. --- ### 3. Pin Configuration (SOT-23-5) | Pin No. | Name | Description | | :--- | :--- | :--- | | 1 | **$\overline{RESET}$** | Active-Low output; stays low if $V_{CC}$ is below threshold or if WDI times out. | | 2 | **GND** | Ground reference. | | 3 | **$\overline{MR}$** | Manual Reset input (active-low). | | 4 | **WDI** | Watchdog Input; must be toggled to prevent reset. | | 5 | **$V_{CC}$** | Power supply input and monitored voltage. | --- ### 4. Typical Application Circuit ```c // Conceptual Logic for Microcontroller Interaction while (true) { Perform_System_Tasks(); // Toggle WDI Pin to prevent ADM823 from resetting the CPU Trigger_Watchdog_Pin(); // If the loop hangs here, the ADM823 will // force a hardware reset after 1.6 seconds. } ``` --- ### 5. Part Number Breakdown * **ADM823**: Series identifier (Supervisory circuit with Watchdog and MR). * **S**: Threshold Voltage code (2.93V). * **Y**: Temperature range (-40°C to +125°C). * **RJ**: Package code (SOT-23). * **Z**: RoHS compliant (Lead-free). * **R7**: 7-inch reel packaging (3,000 pieces).