AP139-18WG-7 Equivalent & Substitute Parts

Part Overview

The AP139-18WG-7 is a linear voltage regulator IC from Diodes Incorporated, delivering a fixed 1.8V output at 300mA in a SOT-25 package. This device is classified as Last Time Buy, indicating end-of-life status. Identifying equivalent and substitute parts is essential for design continuity, long-term supply chain planning, and ensuring uninterrupted production for applications requiring 1.8V regulation at moderate current levels.

Key Parameters

Parameter	Value
Manufacturer Part Number	AP139-18WG-7
Manufacturer	Diodes Incorporated
Category	Power Management (PMIC)
Output Voltage (Fixed)	1.8V
Output Current	300mA
Input Voltage (Max)	5.5V
Package / Case	SC-74A, SOT-753 (SOT-25)
Operating Temperature Range	-40°C ~ 85°C
Product Status	Last Time Buy
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the AP139-18WG-7 is determined by the following critical parameters:

Fixed output voltage of 1.8V
Output current capability of 300mA or greater
Surface mount packaging compatible with SOT-25 footprint
Positive fixed output configuration
Enable control feature
Operating temperature range of -40°C minimum and 85°C maximum
RoHS3 compliance

Substitute parts are grouped into two categories:

Manufacturer Recommended (MFR Recommended): Parts actively recommended by the original manufacturer or component distributors as direct replacements, with active product status and improved specifications.

Parametric Equivalent: Parts meeting the core electrical and mechanical requirements but with variations in secondary parameters such as quiescent current, PSRR, or protection features.

Parameter Comparison

Parameter	AP139-18WG-7	AP7343-18W5-7	MCP1824T-1802E/OT	TPS73218MDBVREP
Manufacturer	Diodes Incorporated	Diodes Incorporated	Microchip Technology	Texas Instruments
Output Voltage	1.8V	1.8V	1.8V	1.8V
Output Current	300mA	300mA	300mA	250mA
Input Voltage (Max)	5.5V	5.25V	6V	5.5V
Quiescent Current	60 µA	60 µA	220 µA	550 µA
Dropout Voltage	Not specified	0.39V @ 300mA	0.32V @ 300mA	0.15V @ 250mA
Package	SOT-25	SOT-25	SOT-23-5	SOT-23-5
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 125°C	-55°C ~ 125°C
Product Status	Last Time Buy	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

AP7343-18W5-7 (Diodes Incorporated): This part is the primary recommended substitute. It maintains identical output voltage and current specifications, operates within the same temperature range, and shares the same SOT-25 package footprint. The AP7343-18W5-7 has active product status, ensuring long-term availability. The reduced maximum input voltage (5.25V vs. 5.5V) and specified dropout voltage (0.39V @ 300mA) must be verified against circuit requirements. Moisture sensitivity is improved (MSL 1 vs. MSL 3).

MCP1824T-1802E/OT (Microchip Technology): This substitute provides 300mA output current with improved dropout voltage (0.32V @ 300mA) and extended operating temperature range (-40°C ~ 125°C). The package is SOT-23-5, requiring PCB layout modification. Quiescent current is elevated (220 µA), which may impact low-power applications. Active product status ensures supply continuity.

TPS73218MDBVREP (Texas Instruments): This part offers the lowest dropout voltage (0.15V @ 250mA) and widest operating temperature range (-55°C ~ 125°C). Output current is reduced to 250mA, making it suitable only for applications with lower current demands. Quiescent current is significantly higher (550 µA). The SOT-23-5 package requires PCB redesign. Active product status and TPS732xx series support provide long-term availability.

All substitute parts are RoHS3 compliant and carry EAR99 ECCN classification, matching the original part's regulatory status.

Frequently Asked Questions (FAQ)

Q: Can AP7343-18W5-7 be used as a direct replacement for AP139-18WG-7?

A: Yes, with circuit verification. Both parts deliver 1.8V at 300mA in SOT-25 packages and operate across -40°C to 85°C. The AP7343-18W5-7 has a lower maximum input voltage (5.25V vs. 5.5V) and specified dropout voltage of 0.39V @ 300mA. Confirm that your input voltage does not exceed 5.25V and that the dropout voltage is acceptable for your application.

Q: What are the package differences between substitute options?

A: AP7343-18W5-7 uses SOT-25 packaging, identical to the original AP139-18WG-7, requiring no PCB layout changes. MCP1824T-1802E/OT and TPS73218MDBVREP both use SOT-23-5 packaging, which has a different footprint and pin configuration, necessitating PCB redesign and schematic updates.

Q: Why does TPS73218MDBVREP have lower output current than the original part?

A: TPS73218MDBVREP is rated for 250mA maximum output current, compared to 300mA for AP139-18WG-7. This part is suitable only for applications requiring 250mA or less. For designs requiring the full 300mA specification, use AP7343-18W5-7 or MCP1824T-1802E/OT.

Q: How do quiescent current differences affect my design?

A: AP139-18WG-7 and AP7343-18W5-7 both draw 60 µA quiescent current. MCP1824T-1802E/OT draws 220 µA, and TPS73218MDBVREP draws 550 µA. In battery-powered or low-power standby applications, higher quiescent current increases power consumption. Select based on your standby power budget.

Q: Are all substitutes RoHS3 compliant?

A: Yes. AP7343-18W5-7, MCP1824T-1802E/OT, and TPS73218MDBVREP are all ROHS3 compliant, matching the original AP139-18WG-7 regulatory status.

Q: What is the significance of the AP139-18WG-7 being Last Time Buy?

A: Last Time Buy status indicates that Diodes Incorporated is discontinuing this part. Existing inventory may be available for a limited time, but long-term supply is not guaranteed. Transitioning to an active substitute part such as AP7343-18W5-7 is recommended for new designs and ongoing production.

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