APX803S05-29SA-7 – 2.93V Open-Drain Microprocessor Reset Supervisor

Product Overview

The APX803S05-29SA-7 is a 3-pin microprocessor reset supervisor / voltage monitor manufactured by Diodes Incorporated. It is designed to monitor a system supply rail and generate an active-low RESET signal when the monitored voltage falls below the reset threshold.

This device is commonly used to protect microcontrollers, processors, DSPs, FPGAs, and digital logic systems from unstable operation during power-up, power-down, brownout, undervoltage, and supply-transient conditions. Diodes’ APX803S datasheet describes the family as a microprocessor reset circuit with an open-drain active-low RESET output, low supply current, and reset thresholds suitable for 2.5V, 3.0V, 3.3V, and 5.0V power-supply monitoring.

Part Number Breakdown

Section	Meaning
APX803S	Diodes microprocessor reset supervisor family
05	Reset delay option, commonly associated with 50ms class delay
29	Reset threshold option, 2.93V class
SA	SOT-23-3 package / pinout option
7	Tape-and-reel packaging option

Competitive Advantages

✔ 3-pin microprocessor reset supervisor

✔ 2.93V-class reset threshold for 3.3V rail monitoring

✔ Active-low RESET output

✔ Open-drain / open-collector output structure

✔ 50ms-class reset delay option

✔ Low supply current for portable equipment

✔ Operates with supply voltage down to 1V class

✔ Compact SOT-23-3 package

✔ Suitable for MCU reset, power-on reset, brownout detection, and embedded voltage supervision

Key Features

1. 2.93V Reset Threshold

The APX803S05-29SA-7 uses a 2.93V-class reset threshold, making it suitable for monitoring 3.3V power rails.

Benefits include:

• Detects undervoltage on 3.3V systems
• Helps prevent MCU malfunction during brownout
• Provides more reliable startup behavior
• Suitable for embedded systems using 3.3V logic rails

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2. Active-Low RESET Output

The device provides an active-low RESET output, which asserts low when the monitored supply voltage falls below the reset threshold.

Benefits include:

• Compatible with many MCU and processor reset pins
• Provides automatic reset during power-up and brownout
• Helps ensure firmware starts from a known state
• Useful for digital systems that require stable supply sequencing

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3. Open-Drain Output Structure

The APX803S family uses an open-drain active-low RESET output. 

Benefits include:

• Allows pull-up to different logic voltages
• Supports wired-OR reset connections
• Useful when multiple reset sources share one reset line
• Flexible for mixed-voltage systems

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4. Low Supply Current

Diodes states that the APX803S family has low supply current, making it suitable for portable equipment. 

Benefits include:

• Reduces standby power consumption
• Suitable for battery-powered devices
• Useful for always-on reset monitoring
• Helps improve energy efficiency in compact systems

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5. Power-On Reset Monitoring

The APX803S05-29SA-7 functions as a power-on reset monitor, holding reset active until the supply voltage reaches a valid operating level and the reset delay expires. TME identifies it as a power-on reset monitor with a 50ms delay time. 

Benefits include:

• Improves startup reliability
• Prevents premature MCU execution
• Helps avoid firmware lockup during unstable supply ramp-up
• Useful for systems with slow or noisy power rails

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6. Compact SOT-23-3 Package

The device is supplied in a 3-pin SOT-23 package, making it suitable for compact PCB layouts. DigiKey lists the part as SOT-23-3. 

Benefits include:

• Saves PCB space
• Easy to place near the MCU reset pin
• Suitable for high-volume SMT assembly
• Good fit for compact embedded modules and consumer electronics

Applications

Microcontroller and Processor Reset

Suitable for:

• MCU reset circuits
• DSP reset lines
• FPGA supervisor circuits
• Embedded processor power monitoring
• Digital control board reset management

The APX803S05-29SA-7 helps ensure the controller starts only after the supply voltage is valid.

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3.3V Power Rail Monitoring

Used in:

• 3.3V logic systems
• Sensor modules
• Communication boards
• IoT controllers
• Industrial embedded devices

The 2.93V threshold is well suited for monitoring undervoltage conditions on 3.3V rails.

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Portable and Battery-Powered Devices

Applicable to:

• Handheld instruments
• Battery-powered sensors
• Wearable electronics
• Consumer electronic modules
• Portable control devices

The low supply current makes it useful for systems that require continuous voltage supervision.

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Industrial and Embedded Systems

Suitable for:

• PLC auxiliary boards
• Industrial controllers
• Data acquisition modules
• Automation sensors
• Monitoring and alarm systems

It helps prevent unpredictable behavior caused by supply dips or brownout events.

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Consumer Electronics

Can be used in:

• Smart home devices
• Set-top boxes
• Remote controls
• Display control boards
• Small appliance controllers

The SOT-23-3 package and simple reset function make it practical for cost-sensitive designs.