3-PIN MICROPROCESSOR RESET CIRCUIT # Technical Documentation: APX80326SAG7 Voltage Supervisor
Manufacturer : DIODES Incorporated
Component Type : Micropower Voltage Supervisor with Manual Reset
---
## 1. Application Scenarios
### 1.1 Typical Use Cases
The APX80326SAG7 is primarily employed as a system monitor and reset controller in embedded electronic systems. Its core function is to ensure a microprocessor or microcontroller begins operation only when the supply voltage is within a stable, specified range, thereby preventing erratic behavior or data corruption during power-up, power-down, or brownout conditions.
Primary Functions:
* Power-On Reset (POR): Generates a guaranteed-length reset pulse (`/RESET` asserted low) when `VCC` rises above the specified threshold (`V_{IT+}`). This holds the host processor in a known state until the supply is stable.
* Brown-Out Detection: Continuously monitors `VCC`. If the supply voltage dips below the falling threshold (`V_{IT-}`), the device immediately asserts the reset signal, safeguarding against low-voltage operation.
* Manual Reset: Incorporates a manual reset input pin (`/MR`). A low signal on this pin, typically from a user push-button, forces an immediate and debounced reset pulse, independent of the `VCC` voltage.
* Watchdog Timer (Optional Functionality): Some variants in the APX803xx family include a watchdog timer. While the specific "-26S" suffix must be confirmed against the datasheet, if present, it resets the system if the microcontroller fails to toggle a specific pin within a programmed timeframe, recovering from software crashes.
### 1.2 Industry Applications
This component is ubiquitous across industries requiring reliable digital control and data integrity.
* Consumer Electronics: Set-top boxes, smart home controllers, routers, gaming peripherals, and audio/video equipment.
* Industrial Automation: Programmable Logic Controllers (PLCs), sensor interfaces, motor drives, and human-machine interfaces (HMIs) where electrical noise and unstable mains power are common.
* Telecommunications: Network switches, modems, and base station control modules.
* Automotive (Non-Safety Critical): Infotainment systems, dashboard displays, and body control modules (ensuring stable boot sequences).
* Medical Devices: Portable monitors, diagnostic equipment where controlled startup is critical (subject to full regulatory validation of the end device).
* IoT and Embedded Systems: Battery-powered or energy-harvesting devices where supply voltages can fluctuate during RF transmission or sensor activation.
### 1.3 Practical Advantages and Limitations
Advantages:
* Ultra-Low Quiescent Current: Typically consumes < 1µA (e.g., 0.75µA), making it ideal for battery-powered and always-on applications.
* High Accuracy: Tight threshold tolerance (e.g., ±1.5% or ±2.5%) ensures predictable and reliable reset behavior across temperature and process variations.
* Integrated Manual Reset: Saves external debouncing components and board space.
* Small Package: Available in SOT-23 and SC-70 packages, minimizing PCB footprint.
* Wide Operating Voltage Range: Typically operates from 1.2V to 5.5V, covering common logic voltages (1.8V, 3.3V, 5.0V).
Limitations:
* Fixed Threshold Voltage: The "26" in the part number typically denotes a fixed reset threshold voltage (e.g., 2.63V for the APX803-26). The threshold cannot be adjusted externally, requiring selection of the correct variant for the target `VCC`.
* Limited Output Drive: The reset output is typically an open-drain or weak CMOS
