## Overview of the ADM1815-R22ART The **ADM1815-R22ART** is a voltage monitoring and supervisory circuit designed by Analog Devices. Its primary function is to monitor a power supply voltage and provide a reset signal to a microprocessor when the voltage falls below a specific threshold. ### Key Specifications | Feature | Specification | | :--- | :--- | | **Reset Threshold** | 2.18V (Nominal) | | **Output Type** | Active-Low, Open-Drain | | **Package** | SOT-23 (3-Lead) | | **Supply Voltage Range** | 1.0V to 5.5V | | **Typical Supply Current** | 10 $\mu$A | | **Reset Timeout Period** | 150 ms (Minimum) | --- ### Core Electronic Components & Architecture The internal architecture of the ADM1815 consists of several critical functional blocks: #### 1. Precision Voltage Reference This is the internal standard against which the monitored $V_{CC}$ is compared. It is temperature-compensated to ensure the 2.18V threshold remains stable across the operating temperature range (-40°C to +105°C). #### 2. Comparator The comparator continuously checks the voltage at the $V_{CC}$ pin. * **Trip Point:** When $V_{CC}$ drops below 2.18V, the comparator triggers the reset logic. * **Hysteresis:** The circuit includes built-in hysteresis to prevent "chattering" (repeated toggling) if the power supply is noisy or hovering exactly at the threshold. #### 3. Open-Drain Output Stage The "R" in the part number indicates an **Open-Drain** output. * **Operation:** To interface with a microprocessor, an external pull-up resistor is required. * **Benefit:** This allows for "wired-OR" logic, where multiple reset sources can be connected to the same reset line. #### 4. Delay Generator (Timer) Once the supply voltage rises back above the threshold (2.18V), the device does not release the reset signal immediately. It waits for approximately **150ms to 250ms**. This ensures the power supply has fully stabilized before the microprocessor begins its boot sequence. --- ### Pin Configuration | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | $\overline{RESET}$ | Active-low output. Remains low when $V_{CC}$ is below threshold. | | 2 | $V_{CC}$ | Power supply input and monitored voltage pin. | | 3 | GND | Ground reference. | --- ### Typical Application Circuit ```mermaid graph LR VCC[5V/3.3V Rail] -->|VCC Pin| ADM(ADM1815) VCC -->|Pull-up Resistor| RESET_LINE ADM -->|RESET Pin| RESET_LINE RESET_LINE -->|Reset Input| MCU(Microprocessor) ADM -->|GND Pin| GND[Ground] ```