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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

Diodes Incorporated AP139-35WL-7

Name: AP139-35WL-7
Brand: Diodes Incorporated
SKU: AP139-35WL-7
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: AP139-35WL-7

Manufacturer:: Diodes Incorporated

Category:: Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

Package:: SC-74A, SOT-753

Datasheet:: AP139-35WL-7.pdf

Description:: IC REG LINEAR 3.5V 300MA SOT25

Quantity:: RFQ Add To RFQ list

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Product details

Overview

AP139-35WL-7 from Diodes Incorporated is a 3.5V fixed-output, 300mA CMOS low-dropout linear regulator in SOT25 package, featuring 45μA typical quiescent current, 0.45V max dropout at 300mA, ±2% output voltage accuracy, and integrated thermal shutdown/current limiting-designed for battery-powered portable electronics requiring stable low-noise supply.

For engineers reviewing the AP139-35WL-7 datasheet, AP139-35WL-7 pinout, AP139-35WL-7 application, or AP139-35WL-7 equivalent, key selection considerations include dropout performance at 300mA load, bypass capacitor dependency (10nF required), stability with ≥1.0μF low-ESR output capacitors, and enable-pin logic behavior (active-low EN with <0.1μA leakage).

Technical Context

The AP139-35WL-7 employs a pMOS pass transistor architecture with internal voltage reference and error amplifier feedback loop, enabling precise regulation across input range 2.7V–5.5V. Its low-quiescent-current design maintains 45μA operation under no-load while supporting full 300mA output without external bias components.

Thermal shutdown activates at +130°C junction temperature with +20°C hysteresis, and current limiting engages at 300mA (min) to 450mA (max), switching regulator operation from voltage mode to current mode during overload-ensuring robust protection without external circuitry.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 3.5V ±2% - ensures stable rail for 3.3V-tolerant I/O or low-voltage microcontrollers without external resistive divider.
Max Output Current	300mA guaranteed - supports moderate-power peripherals like BLE radios or sensor hubs without thermal derating in SOT25.
Dropout Voltage	≤0.45V at 300mA - enables regulation down to VIN = 3.95V, critical for single-cell Li-ion (3.0–4.2V) or dual-cell alkaline systems.
Quiescent Current	45μA typ / 60μA max - extends battery life in always-on monitoring devices; drops to <2μA in shutdown via EN pin.
PSRR @ 1kHz	75dB with 10nF BYP capacitor - suppresses switching noise from upstream DC/DC converters in mixed-signal systems.
Stability Condition	Stable with ≥1.0μF ceramic output capacitor - eliminates need for high-ESR tantalum, reducing BOM cost and board space.
Enable Threshold	V_EH = 1.7V (ON), V_EL = 0.8V (OFF) - compatible with 1.8V/3.3V GPIO without level-shifting.

Pinout & Package

SOT25 (5-pin, lead-free, RoHS-compliant, "Green" halogen/antimony-free) package with 1.6mm × 2.9mm footprint and 0.95mm height-optimized for space-constrained handheld PCBs.

Pin/Terminal	Circuit Role	Design Meaning
VIN (Pin 1)	Input power supply	Accepts 2.7–5.5V; requires ≥0.1μF input capacitor close to pin for transient immunity.
GND (Pin 2)	Power ground reference	Low-impedance return path for all internal circuits; must connect to quiet analog ground plane.
EN (Pin 3)	Active-low enable control	Pulling ≤0.8V disables regulator and reduces IQ to <2μA; floating or >1.7V enables operation.
BYP (Pin 4)	Bypass capacitor connection	Requires 10nF capacitor to GND to improve PSRR and noise rejection; critical for low-noise operation.
VOUT (Pin 5)	Regulated output	Delivers 3.5V ±2% at up to 300mA; stable with ≥1.0μF low-ESR ceramic capacitor directly at pin.

Key Features

Feature	Design Value
Ultra-low quiescent current	45μA typical enables >1-year battery life in coin-cell–powered IoT sensors with 10μA average system load.
Low-noise regulation	10nF BYP capacitor enables 75dB PSRR at 1kHz-critical for ADC reference supplies and RF front-end biasing.
Robust protection suite	Integrated thermal shutdown (+130°C) and current limit (300mA min) eliminate need for external fault management circuitry.
Wide input compatibility	2.7–5.5V input range supports direct connection to USB VBUS, Li-ion cells, or multi-cell alkaline stacks.
Small-footprint packaging	SOT25 footprint (1.6×2.9mm) reduces PCB area by 40% vs. SOT23-5, ideal for wearables and compact modules.

Applications

Wearable Health Monitors

Bluetooth Low Energy Peripherals

Use Scenario: Continuous ECG/PPG sensing powered by CR2032 or rechargeable Li-Poly cell.

IC Role / Device Role / Timing Role: Primary 3.5V supply for analog front-end and BLE SoC core domain.

Use Value: 45μA IQ extends battery runtime beyond 6 months; 0.45V dropout allows operation until cell voltage drops to 3.95V.

Use Scenario: Compact BLE beacon or smart tag with motion sensor and flash memory.

IC Role / Device Role / Timing Role: Stable 3.5V rail for Nordic nRF52832 SoC VDD and external SPI flash.

Use Value: 75dB PSRR at 1kHz prevents RF switching noise from corrupting sensor data acquisition.

USB-Powered Test Instruments

Smart Home Sensor Nodes

Use Scenario: Portable multimeter or logic analyzer powered directly from USB 5V.

IC Role / Device Role / Timing Role: Local LDO for precision op-amp and ADC reference voltage generation.

Use Value: ±2% output accuracy and 50ppm/°C tempco ensure measurement repeatability across -40°C to +85°C ambient.

Use Scenario: Battery-operated Zigbee/Thread temperature/humidity node with MCU and radio.

IC Role / Device Role / Timing Role: Main supply for Silicon Labs EFR32MG21 and environmental sensors.

Use Value: Active-low EN pin enables MCU-controlled deep-sleep mode, reducing system IQ to sub-μA levels.

Equivalent & Alternatives

The following parts are listed as comparable options for similar LDO regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
AP7343-35SAG-7	Successor device: 300mA, 3.5V, 25μA IQ, improved PSRR (80dB @1kHz), same SOT25 package.	Designed for new designs; supports tighter load regulation (0.3% vs. 1%) and lower thermal resistance (θ_JA = 200°C/W).	Select for new projects requiring longer battery life and higher noise immunity; pin-compatible drop-in replacement.
MCP1703T-3502E/MB	Microchip 250mA LDO: 3.5V, 4μA IQ, but only 250mA output and higher dropout (0.6V @250mA).	Better ultra-low-power performance but insufficient current headroom for 300mA peak loads (e.g., BLE transmit bursts).	Consider only if system peak current remains ≤250mA and standby IQ is primary concern over dynamic capability.

Compared with AP139-35WL-7, AP7343-35SAG-7 offers lower IQ and better PSRR in identical form factor, while MCP1703T-3502E/MB trades output current for extreme low-power operation-making AP139-35WL-7 optimal where 300mA delivery and proven field reliability are prioritized over newest-generation specs.

Availability

AP139-35WL-7 is available at Aetrix Electronics and suitable for battery-powered portable electronics, wearable health monitors, and USB-powered test instrumentation requiring stable component supply and long-term legacy support.

Supply support for AP139-35WL-7 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in power management, signal integrity, and protection solutions for consumer, industrial, and automotive markets.

The AP139 belongs to Diodes' low-noise CMOS LDO product line, engineered specifically for space-constrained, battery-sensitive applications demanding high accuracy, low dropout, and integrated protection-without external compensation components.

FAQ

What is the minimum input voltage required for AP139-35WL-7 to maintain regulation at 300mA?

The minimum input voltage is calculated as V_OUT + V_DROPOUT = 3.5V + 0.45V = 3.95V. This value is confirmed in the datasheet's Electrical Characteristics table under Dropout Voltage test condition (I_O = 300mA, V_OUT ≥ 2.8V). Operation below this voltage causes output collapse.

Can AP139-35WL-7 operate without the 10nF bypass capacitor on the BYP pin?

No. The datasheet explicitly states that "a 10nF capacitor is necessary to be placed in between Bypass and Ground" for low-noise, regulated supply operation. Omitting it degrades PSRR by up to 25dB at 1kHz and increases output voltage noise, compromising performance in sensitive analog or RF applications.

Is AP139-35WL-7 qualified for automotive applications?

No. While Diodes offers AEC-Q100-qualified variants in other LDO families, the AP139 series-including AP139-35WL-7-is not AEC-Q100 certified. The datasheet notes automotive qualification requires separate change control and PPAP capability, which this part does not possess.

What happens to the output when the EN pin is left floating?

The EN pin "normally floats high" per the Functional Description section, enabling normal regulator operation. Internal pull-up ensures V_EN exceeds 1.7V threshold, so V_OUT regulates as expected. No external pull-up resistor is required unless noise immunity in high-EMI environments is needed.

AP139-35WL-7 Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

Package/Case:: SC-74A, SOT-753

Packaging:: Tape & Reel (TR)

Product Status:: Discontinued at Digi-Key

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 5.5V

Voltage - Output (Min/Fixed):: 3.5V

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.45V @ 300mA

Current - Output:: 300mA

Current - Quiescent (Iq):: 60 µA

Current - Supply (Max):: -

PSRR:: 75dB ~ 30dB (1KHz ~ 100KHz)

Control Features:: Enable

Protection Features:: Over Current, Over Temperature, Short Circuit

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-25

AP139-35WL-7 FAQ

1.How can I place an order for AP139-35WL-7 through Aetrix?

Please submit a Request for Quotation (RFQ) for AP139-35WL-7 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for AP139-35WL-7 reliable?

The price and inventory of AP139-35WL-7 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AP139-35WL-7 is usually 5 days.

3.What payment methods are accepted for AP139-35WL-7?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AP139-35WL-7 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for AP139-35WL-7?

AP139-35WL-7 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your AP139-35WL-7 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for AP139-35WL-7?

For technical support, including AP139-35WL-7 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AP139-35WL-7 requirements.

6.How does Aetrix verify that AP139-35WL-7 is sourced from the original manufacturer or authorized distributors?

All AP139-35WL-7 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AP139-35WL-7 meets industry standards.

7.What is the process for return or replacement of AP139-35WL-7?

All AP139-35WL-7 units undergo pre-shipment inspection (PSI). If there is an issue with AP139-35WL-7, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The AP139-35WL-7 part is unused and in its original packaging.

Return procedure for AP139-35WL-7:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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