S-80139ALMC-JAYT2G 3.9V Voltage Detector IC

ElecSuppliers Part Number GuideAug 22, 2026

S-80139ALMC-JAYT2G is a voltage detector IC from the ABLIC S-801 series. It is designed to monitor a power supply voltage and provide a reset signal when the monitored voltage falls below a defined threshold.

The device is particularly useful in systems where a microcontroller or other digital circuit needs reliable protection against unstable or insufficient supply voltage.

S-80139ALMC-JAYT2G Key Specifications

S-80139ALMC-JAYT2G monitors a single voltage and has a nominal detection threshold of 3.9 V with approximately ±2% accuracy.

The device operates from a supply voltage ranging from approximately 0.95 V to 10 V and is designed for an operating temperature range of -40°C to +85°C.

It uses a compact SOT-23-5 surface-mount package and provides an active-low CMOS push-pull output.

The reset delay is approximately 50 ms for this version, allowing the monitored supply to stabilize before the system is released from reset.

3.9V Voltage Detector

A voltage detector monitors a supply rail and determines whether the voltage is within the required operating range.

For a system operating around a 5 V supply, a 3.9 V detection threshold can be used to identify an undervoltage condition.

When the monitored voltage falls below the detection level, the output changes state and can force a connected microcontroller or digital system into reset.

This prevents the processor from continuing to operate when the supply voltage is too low for reliable operation.

S-80139ALMC-JAYT2G Reset Function

Reset supervision is especially important during power-up and power-down.

When a circuit is powered on, the supply voltage may take some time to reach a stable level. If the microcontroller starts executing code before the supply is stable, unpredictable operation can occur.

S-80139ALMC-JAYT2G can hold the system in a reset state while the monitored voltage remains below the required threshold.

After the supply becomes stable, the reset signal is released following the built-in delay.

This provides a simple way to improve system startup reliability.

50ms Reset Delay

The built-in reset delay is an important feature of S-80139ALMC-JAYT2G.

The approximately 50 ms delay prevents the output from immediately changing state whenever the monitored voltage briefly crosses the detection threshold.

This can help avoid unwanted system resets caused by short-duration power disturbances.

The delay can also give a microcontroller and its associated power supply enough time to stabilize after power is applied.

Active-Low CMOS Output

S-80139ALMC-JAYT2G provides an active-low reset output.

An active-low reset signal is commonly used with microcontrollers and digital ICs.

When an undervoltage condition is detected, the reset output can be asserted to place the connected system into its defined reset state.

The push-pull output structure provides active drive in both logic states, making it suitable for directly interfacing with many digital control inputs.

S-80139ALMC-JAYT2G Applications

S-80139ALMC-JAYT2G can be used in a wide range of electronic equipment.

Typical applications include microcontroller systems, consumer electronics, industrial control equipment, power monitoring circuits, embedded systems and battery-powered equipment.

It can also be used in systems where reliable power-on reset behavior is required.

The device is particularly useful when the system cannot tolerate unpredictable processor operation during an undervoltage condition.

Microcontroller Reset Protection

Modern microcontrollers can be sensitive to supply-voltage changes.

If the supply falls below the minimum operating voltage, the processor may execute instructions incorrectly, corrupt memory or enter an undefined state.

A dedicated voltage detector provides an independent monitoring circuit.

Instead of relying entirely on software or the microcontroller's internal reset function, the external supervisor can monitor the supply and generate a hardware reset signal.

This approach can improve reliability in systems with variable or unstable power sources.

S-80139ALMC-JAYT2G Power Supply Monitoring

The device can monitor a single power rail.

For example, in a 5 V embedded system, the 3.9 V threshold can be used to detect when the supply has dropped significantly below its normal operating level.

The detector can then signal the processor or control circuit that the supply is no longer within the desired range.

This can also be useful during power-down, allowing the system to enter a controlled reset state before the supply becomes too low.

SOT-23-5 Package

S-80139ALMC-JAYT2G uses a compact SOT-23-5 package.

The five-pin package requires little PCB space, making it suitable for compact control boards and densely populated electronic equipment.

Surface-mount construction also makes the device suitable for automated PCB assembly.

When replacing the component, the exact pin configuration should be checked because different voltage supervisor ICs using similar SOT-23 packages may have different pin assignments.

Low-Power Voltage Monitoring

Power consumption is an important consideration for supervisory circuits, especially in battery-powered products.

The S-801 series is designed for low current consumption, allowing the voltage detector to remain active without becoming a significant load on the system power supply.

This is useful in products that spend long periods in standby or low-power modes.

The supervisor can continue monitoring the supply while the main processor or other system functions are disabled.

S-80139ALMC-JAYT2G Replacement

When selecting a replacement for S-80139ALMC-JAYT2G, the 3.9 V detection threshold should be matched first.

The reset delay, output configuration, supply-voltage range and operating temperature should also be checked.

The SOT-23-5 package alone is not sufficient to determine compatibility.

A replacement with a different reset polarity or different delay time could change the behavior of the entire power-management circuit.

For direct replacement applications, the pin configuration should therefore be verified carefully.

S-80139ALMC-JAYT2G PCB Design

The voltage detector should be positioned close to the power rail being monitored.

The supply and ground connections should use short PCB traces where practical.

The reset signal should also be routed carefully, particularly in systems where the line connects directly to a microcontroller reset input.

Good PCB layout can reduce the possibility of unwanted noise being coupled into the voltage-monitoring circuit.

S-80139ALMC-JAYT2G for Embedded Systems

S-80139ALMC-JAYT2G provides a simple hardware solution for monitoring a 3.9 V supply threshold and generating an active-low reset signal.

Its single-channel voltage monitoring, approximately 50 ms reset delay, CMOS push-pull output and compact SOT-23-5 package make it suitable for embedded systems, microcontroller boards and other power-sensitive electronic equipment.

For new designs, engineers should evaluate the detection threshold, reset delay, supply range, output configuration and operating temperature together. For replacement applications, matching the complete electrical characteristics and pin configuration is essential.