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

Diodes Incorporated AP2125K-4.2TRG1

Name: AP2125K-4.2TRG1
Brand: Diodes Incorporated
SKU: AP2125K-4.2TRG1
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: AP2125K-4.2TRG1

Manufacturer:: Diodes Incorporated

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

Package:: SC-74A, SOT-753

Datasheet:: AP2125K-4.2TRG1.pdf

Description:: IC REG LINEAR 4.2V 300MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Inventory:2,998

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Product details

Overview

AP2125K-4.2TRG1 from Diodes Incorporated is a 300mA, fixed-output 4.2V CMOS low-dropout (LDO) regulator in SC-70-5 package, featuring 50µV_rms output noise, ±2% output voltage accuracy, and 65mV dropout at 100mA - optimized for lithium-ion battery-powered portable electronics requiring stable, ultra-low-noise supply rails.

For engineers reviewing the AP2125K-4.2TRG1 datasheet, AP2125K-4.2TRG1 pinout, AP2125K-4.2TRG1 application, or AP2125K-4.2TRG1 equivalent, key selection criteria include its 0.01µA standby current, compatibility with low-ESR ceramic capacitors, thermal shutdown at +160°C, and enable-controlled power sequencing in space-constrained designs.

Technical Context

The AP2125K-4.2TRG1 integrates a precision voltage reference, error amplifier, resistor network for fixed 4.2V output, active-high CE control, overcurrent protection, and overtemperature shutdown (OTSD). Its CMOS architecture enables ultra-low quiescent current (60µA typical) and minimal load-dependent dropout variation.

It operates across -40°C to +85°C ambient, supports input voltages from (V_OUT + 0.5)V up to 6V, and maintains 70dB PSRR at 100Hz–1kHz - critical for powering noise-sensitive analog/RF circuitry in battery-operated systems where supply rail integrity directly impacts signal fidelity.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 4.2V ±2% - matches Li-ion full-charge voltage for direct battery regulation without external feedback.
Max Output Current	300mA minimum - sufficient for powering baseband processors, PMIC subsystems, or RF front-end ICs in handheld devices.
Dropout Voltage	65mV at 100mA - enables >98% efficiency at light-to-moderate loads when VIN = 4.25V, extending battery runtime.
RMS Output Noise	50µV_rms (10Hz–100kHz) - prevents jitter injection into ADC references or PLL VCO supplies in mixed-signal applications.
Quiescent Current	60µA typical - minimizes no-load battery drain during system sleep modes, critical for multi-day standby operation.
Standby Current	0.01µA typical - reduces leakage to sub-nA level when CE = low, enabling true zero-power shutdown states.
PSRR	65dB typical at 1kHz - suppresses switching noise from upstream DC-DC converters feeding the LDO input.
Thermal Shutdown	+160°C with +25°C hysteresis - protects against sustained overload or PCB thermal runaway without latch-up.

Pinout & Package

AP2125K-4.2TRG1 uses the SC-70-5 surface-mount package (1.25mm × 1.65mm × 0.95mm), optimized for high-density portable PCB layouts. Thermal resistance θ_JA is 300°C/W (no heatsink).

Pin/Terminal	Circuit Role	Design Meaning
1	VIN	Input supply connection; accepts 4.7V to 6V (min VIN = VOUT + 0.5V = 4.7V) with internal ESD protection rated to 6kV HBM.
2	GND	Power ground reference; must be low-impedance connection to minimize noise coupling and ensure regulation stability.
3	NC	No internal connection; left unconnected per datasheet - not usable as thermal pad or auxiliary terminal.
4	CE	Active-high enable input; logic high ≥1.5V enables regulation, logic low ≤0.4V disables output and reduces I_Q to 0.01µA.
5	VOUT	Regulated 4.2V output; requires 1µF ceramic capacitor (low-ESR) on board for stability and transient response.

Key Features

Feature	Design Value
Ultra-low noise regulation	50µV_rms output noise enables clean power for RF transceivers and high-resolution ADCs without additional filtering.
Sub-100mV dropout	65mV dropout at 100mA allows operation down to VIN = 4.265V - critical for maintaining regulation as Li-ion voltage declines near end-of-charge.
Enable-controlled shutdown	0.01µA standby current under CE = low extends shelf life and enables firmware-controlled power gating in IoT edge nodes.
Low-ESR capacitor compatible	Stable with 1µF ceramic output capacitor - eliminates need for bulky tantalum or electrolytic caps, reducing BOM cost and board area.
±2% output accuracy	Tight tolerance ensures reliable biasing of 4.2V-referenced circuits (e.g., battery fuel gauges, charge termination comparators) without calibration.
Overtemperature protection	+160°C shutdown with +25°C hysteresis prevents thermal damage during sustained overload while allowing automatic recovery after cooling.

Applications

Smartphone Baseband Power

Portable Medical Sensor

Use Scenario: Powers baseband processor core voltage rail in GSM/CDMA handsets during active call mode and deep sleep cycles.

IC Role / Device Role / Timing Role: Primary 4.2V LDO delivering regulated supply to SoC I/O and memory interfaces with fast load transient response.

Use Value: 50µV_rms noise prevents bit errors in digital baseband signaling; 0.01µA standby current extends 7-day standby time by >12 hours vs. higher-I_Q alternatives.

Use Scenario: Supplies analog front-end (AFE) and microcontroller in handheld ECG or pulse oximeter units.

IC Role / Device Role / Timing Role: Low-noise 4.2V source for precision op-amps and SAR ADC reference buffers, synchronized with MCU wake-up events via CE pin.

Use Value: ±2% output accuracy ensures consistent sensor gain calibration; 65mV dropout preserves regulation until battery reaches 4.265V - matching Li-ion discharge curve endpoint.

USB-C Power Bank Output Stage

Wearable Fitness Tracker

Use Scenario: Provides final regulated 4.2V output to USB-C PD sink ports in compact power banks using single-cell Li-ion input.

IC Role / Device Role / Timing Role: Post-regulation stage ensuring compliant 4.2V ±5% output per USB Battery Charging spec, controlled by host MCU via CE.

Use Value: 300mA rating supports dual-port simultaneous charging; thermal shutdown prevents overheating during 45°C ambient operation in sealed enclosures.

Use Scenario: Powers Bluetooth LE radio, accelerometer, and OLED display in wrist-worn trackers with 24/7 wearability requirements.

IC Role / Device Role / Timing Role: Always-on 4.2V rail for RTC and sensor hub, with CE pin toggled by motion-detect interrupt to reduce average I_Q.

Use Value: 60µA quiescent current enables >14-day battery life on 120mAh cell; SC-70-5 footprint saves 40% board area vs. SOT-23-5 alternatives.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MCP1700T-4202E/TT	250mA max output, 115mV dropout at 100mA, 30µV_rms noise, SOT-23-3 package	Lacks enable pin and thermal shutdown; limited to lower-current, non-safety-critical functions	Select when board space is constrained to 3-pin footprint and thermal protection is handled externally.
TPS7A2042PDBVR	300mA, 140mV dropout at 100mA, 7µV_rms noise, 25µA I_Q, SOT-23-5	Lower noise but higher dropout; requires 1.6V min input headroom vs. AP2125's 0.5V	Prefer for ultra-low-noise analog rails where input voltage margin exceeds 1.6V and thermal shutdown is secondary.

Compared with MCP1700T-4202E/TT, AP2125K-4.2TRG1 adds enable control and OTSD for system-level safety; versus TPS7A2042PDBVR, it trades 23µV_rms less noise for 75mV lower dropout - making it superior for Li-ion systems operating near end-of-charge voltage.

Availability

AP2125K-4.2TRG1 is available at Aetrix Electronics and suitable for smartphone baseband power, portable medical sensors, USB-C power banks, and wearable fitness trackers requiring stable component supply with guaranteed long-term manufacturability.

Supply support for AP2125K-4.2TRG1 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 semiconductor company specializing in discrete, analog, and mixed-signal ICs, with emphasis on power management, signal integrity, and connectivity solutions for consumer, industrial, and automotive markets.

The AP2125 series belongs to Diodes' high-performance LDO portfolio, designed specifically for battery-powered portable electronics demanding ultra-low noise, minimal dropout, and nanoscale quiescent current in miniature packages.

FAQ

What is the minimum input voltage required for AP2125K-4.2TRG1 to maintain regulation?

The AP2125K-4.2TRG1 requires VIN ≥ VOUT + 0.5V = 4.7V to guarantee regulation across temperature and load. At 100mA output, dropout is 65mV, so regulation holds down to VIN = 4.265V - but the 0.5V headroom ensures stability under worst-case line/load/temperature conditions per datasheet specifications.

Can AP2125K-4.2TRG1 be used with ceramic output capacitors smaller than 1µF?

No - the datasheet specifies 1µF ceramic (X5R/X7R) as the minimum stable output capacitance. Using <1µF risks oscillation or degraded transient response due to insufficient phase margin; ESR must remain below 100mΩ, and layout must minimize trace inductance between VOUT and capacitor pads.

Does AP2125K-4.2TRG1 support reverse current blocking?

No - the AP2125K-4.2TRG1 lacks internal reverse-current protection. If VIN drops below VOUT (e.g., during hot-swap or battery swap), current can flow backward from VOUT to VIN through the pass device. An external Schottky diode in series with VIN is required for reverse-blocking applications.

How does the CE pin behave during power-up and power-down sequences?

The CE pin has no internal pull-up/down; it must be actively driven. During power-up, CE should be held low until VIN stabilizes above 4.7V, then asserted high to enable output. During power-down, driving CE low disables VOUT within 10µs and reduces current draw to 0.01µA - enabling precise sequencing in multi-rail systems.

AP2125K-4.2TRG1 Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

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

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 6V

Voltage - Output (Min/Fixed):: 4.2V

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.3V @ 300mA

Current - Output:: 300mA

Current - Quiescent (Iq):: 90 µA

Current - Supply (Max):: -

PSRR:: 65dB (100Hz ~ 1kHz)

Control Features:: Enable

Protection Features:: Over Current, Over Temperature

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-5

AP2125K-4.2TRG1 FAQ

1.How can I place an order for AP2125K-4.2TRG1 through Aetrix?

Please submit a Request for Quotation (RFQ) for AP2125K-4.2TRG1 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 AP2125K-4.2TRG1 reliable?

The price and inventory of AP2125K-4.2TRG1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AP2125K-4.2TRG1 is usually 5 days.

3.What payment methods are accepted for AP2125K-4.2TRG1?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AP2125K-4.2TRG1 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for AP2125K-4.2TRG1?

AP2125K-4.2TRG1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your AP2125K-4.2TRG1 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 AP2125K-4.2TRG1?

For technical support, including AP2125K-4.2TRG1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AP2125K-4.2TRG1 requirements.

6.How does Aetrix verify that AP2125K-4.2TRG1 is sourced from the original manufacturer or authorized distributors?

All AP2125K-4.2TRG1 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 AP2125K-4.2TRG1 meets industry standards.

7.What is the process for return or replacement of AP2125K-4.2TRG1?

All AP2125K-4.2TRG1 units undergo pre-shipment inspection (PSI). If there is an issue with AP2125K-4.2TRG1, 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 AP2125K-4.2TRG1 part is unused and in its original packaging.

Return procedure for AP2125K-4.2TRG1:

1.Submit a request within 90 days.

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

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