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

STMicroelectronics LDK120C31R

Name: LDK120C31R
Brand: STMicroelectronics
SKU: LDK120C31R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDK120C31R

Manufacturer:: STMicroelectronics

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

Package:: 5-TSSOP, SC-70-5, SOT-353

Datasheet:: LDK120C31R.pdf

Description:: IC REG LIN 3.1V 200MA SOT323-5

Quantity:: RFQ Add To RFQ list

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Inventory:2,759

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Product details

Overview

LDK120C31R from STMicroelectronics is a 3.1 V fixed-output, 200 mA low-dropout linear regulator with 100 mV typical dropout at 100 mA, 100 µA max quiescent current, and ±2.0% output voltage tolerance at 25 °C - designed for power-sensitive mobile and portable systems requiring stable low-noise bias.

For engineers reviewing the LDK120C31R datasheet, LDK120C31R pinout, LDK120C31R application, or LDK120C31R equivalent, this page delivers verified electrical specs, SOT323-5L package details, enable-controlled shutdown behavior, ceramic-capacitor compatibility (1 µF), and real-world use cases in battery-powered digital systems.

Technical Context

The LDK120C31R implements a PMOS pass transistor architecture enabling ultra-low dropout and minimal load-dependent regulation error (0.006 %/mA). Its internal bandgap reference and error amplifier deliver tight DC accuracy across –40 °C to 125 °C, while integrated thermal shutdown (160 °C) and short-circuit current limiting (400 mA) ensure robust operation under fault conditions.

It features logic-controlled enable (VEN thresholds: 0.4 V low, 1.2 V high), supports bypass capacitor filtering (optional 10 nF on BYP pin for 51 µV_RMS noise), and maintains stability with 1–22 µF ceramic output capacitors - eliminating need for ESR-tuned electrolytics.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 3.1 V ±2.0% at 25 °C - ensures precise rail generation for 3.3 V-tolerant I/O or low-voltage logic without external feedback.
Max output current	200 mA guaranteed - sufficient to power baseband processors, RF front-ends, or sensor subsystems in compact handheld devices.
Dropout voltage	100 mV typ. at 100 mA - enables operation down to VIN = 3.2 V, extending battery runtime in single-cell Li-ion (3.0–4.2 V) applications.
Quiescent current	60 µA typ. (1 µA in OFF mode) - minimizes standby drain, critical for always-on functions like RTC or wake-up circuitry.
Output noise	51 µV_RMS (10 Hz–100 kHz, with 10 nF BYP cap) - meets stringent analog supply requirements for ADCs, audio codecs, or RF synthesizers.
Supply rejection	55 dB (120 Hz–10 kHz) - suppresses ripple from noisy switching converters, enabling clean LDO post-regulation in hybrid power architectures.
Operating temperature	–40 °C to 125 °C junction - qualified for automotive infotainment modules and industrial portable test equipment.

Pinout & Package

LDK120C31R is packaged in SOT323-5L - a 1.8 × 2.0 mm, 5-pin surface-mount package with exposed thermal pad (not electrically connected), optimized for space-constrained PCB layouts and moderate power dissipation (R_thJA = 246 °C/W).

Pin	Circuit Role	Design Meaning
1	IN	Main input supply connection (1.9–5.5 V); requires local 1 µF ceramic decoupling (C_IN) near pin.
2	GND	Power ground reference for regulator core and feedback network; must be low-impedance return path.
3	EN	Active-high enable control: <0.4 V = shutdown (<1 µA I_Q), >1.2 V = active; compatible with 1.8 V/3.3 V GPIO.
4	BYP	Bypass pin for optional 10 nF capacitor to reduce output noise; left floating if unused (no board routing required).
5	OUT	Regulated 3.1 V output; stable with 1–22 µF ceramic C_OUT; layout must minimize trace inductance for transient response.

Key Features

Feature	Design Value
Ultra-low noise with bypass option	51 µV_RMS (10 Hz–100 kHz) when 10 nF cap applied to BYP pin - enables direct powering of noise-sensitive analog blocks.
Ceramic capacitor compatibility	Stable with 1 µF C_OUT (min), eliminating need for tantalum or aluminum electrolytic - reduces BOM cost and improves reliability.
Logic-controlled shutdown	EN pin draws only 100 nA; achieves <1 µA total device current in OFF state - extends shelf life and battery hold time.
Wide input voltage range	Operates from 1.9 V to 5.5 V - supports single-cell Li-ion, Li-polymer, and dual-cell alkaline/NiMH battery inputs without pre-regulation.
Integrated protection	Thermal shutdown (160 °C, 20 °C hysteresis) + constant-current short-circuit limit (400 mA) - prevents damage during overloads or PCB faults.

Applications

Mobile Phone Baseband Power

Digital Still Camera Sensor Bias

Use Scenario: Supplying 3.1 V bias to CMOS image sensor analog front-end and ISP core during capture mode.

IC Role / Device Role / Timing Role: Low-noise post-regulator delivering clean, ripple-free voltage to ADC reference and PLL VCO circuits.

Use Value: 51 µV_RMS noise and 55 dB SVR prevent quantization noise and clock jitter, preserving image SNR and color fidelity.

Use Scenario: Powering flash memory interface and SD card controller in compact point-and-shoot cameras.

IC Role / Device Role / Timing Role: Stable 3.1 V rail generator with fast load transient response (<5 µs recovery) for burst data writes.

Use Value: 0.006 %/mA load regulation and 100 mV dropout maintain voltage within spec during 0→200 mA step loads, avoiding bus timeouts.

Bluetooth Headset Audio Codec

Industrial Handheld Scanner

Use Scenario: Providing 3.1 V supply to stereo DAC, headphone amplifier, and Bluetooth radio SoC in ultra-low-power wearables.

IC Role / Device Role / Timing Role: Always-on LDO with 1 µA shutdown current supporting quick wake-from-sleep transitions.

Use Value: Sub-µA OFF-mode current extends battery life beyond 7 days in standby, while EN pin allows host MCU to manage power sequencing.

Use Scenario: Regulating main system voltage for ARM Cortex-M microcontroller, barcode laser driver, and display backlight in ruggedized field tools.

IC Role / Device Role / Timing Role: Primary 3.1 V power source operating across –40 °C to 85 °C ambient with thermal foldback.

Use Value: 125 °C max junction rating and 160 °C thermal shutdown protect against enclosure heat buildup during continuous scanning duty cycles.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6219B312MR-G	3.1 V fixed, 200 mA, 150 mV dropout @ 100 mA, 15 µA I_Q, SOT23-5	Lower quiescent current but higher dropout - less suitable for deep-discharge battery operation below 3.25 V.	Select when lowest standby power dominates over input headroom constraints.
Diodes AP7361-C31S-7	3.1 V fixed, 300 mA, 250 mV dropout @ 150 mA, 60 µA I_Q, SOT23-5	Higher current rating and same I_Q, but larger dropout and no BYP pin - lacks ultra-low-noise capability.	Select when future-proofing for higher load margins is needed and noise is secondary.

Compared with XC6219B312MR-G and AP7361-C31S-7, the LDK120C31R uniquely balances ultra-low dropout (100 mV), ultra-low noise (51 µV_RMS with BYP), and wide temperature support (–40 °C to 125 °C), making it optimal for noise-critical, battery-headroom-limited designs where thermal robustness is essential.

Availability

LDK120C31R is available at Aetrix Electronics and suitable for mobile phones, digital still cameras, Bluetooth headsets, and industrial handheld scanners requiring stable component supply with full production lifecycle assurance through July 2026.

Supply support for LDK120C31R 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The LDK120 series targets ultra-low-power, low-noise portable electronics - specifically engineered to replace legacy LDOs in space- and battery-constrained devices where dropout, noise, and shutdown current directly impact end-product runtime and signal integrity.

FAQ

What is the minimum input voltage required for LDK120C31R to maintain regulation at full 200 mA load?

The minimum input voltage is calculated as V_OUT + V_DROP = 3.1 V + 300 mV (max dropout at 200 mA, 40–125 °C) = 3.4 V. Below this, output voltage drops linearly with input; operation below 3.4 V is permissible only if reduced output voltage is acceptable for the downstream circuit.

Can LDK120C31R be used with a 1 µF ceramic output capacitor without stability issues?

Yes - the datasheet explicitly states stability with C_OUT = 1 µF ceramic (X5R/X7R), and Figure 25 confirms the 1–22 µF range is within the stable region for fixed versions. No series resistance or special dielectric is required; standard 0603/0805 MLCCs are fully supported.

Is the BYP pin mandatory for achieving 51 µV_RMS noise performance?

Yes - the 51 µV_RMS figure (Table 4, footnote 2) applies only when a 10 nF capacitor is placed between BYP and GND. Without it, noise rises to 148 µV_RMS. The BYP pin must be left floating (not grounded) if unused; routing or soldering to GND degrades noise performance.

Does LDK120C31R support reverse current blocking when input is disconnected?

No - the LDK120C31R uses a PMOS pass device that does not inherently block reverse current. If the output voltage exceeds the input (e.g., during hot-swap or backup battery scenarios), current can flow backward from OUT to IN. An external reverse-blocking diode or ideal diode controller is required for such topologies.

LDK120C31R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 5-TSSOP, SC-70-5, SOT-353

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 5.5V

Voltage - Output (Min/Fixed):: 3.1V

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.3V @ 200mA

Current - Output:: 200mA

Current - Quiescent (Iq):: 60 µA

Current - Supply (Max):: 100 µA

PSRR:: 55dB (120Hz ~ 10kHz)

Control Features:: Enable

Protection Features:: Over Current, Over Temperature

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-323-5

LDK120C31R FAQ

1.How can I place an order for LDK120C31R through Aetrix?

Please submit a Request for Quotation (RFQ) for LDK120C31R 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 LDK120C31R reliable?

The price and inventory of LDK120C31R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDK120C31R is usually 5 days.

3.What payment methods are accepted for LDK120C31R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDK120C31R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDK120C31R?

LDK120C31R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDK120C31R 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 LDK120C31R?

For technical support, including LDK120C31R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDK120C31R requirements.

6.How does Aetrix verify that LDK120C31R is sourced from the original manufacturer or authorized distributors?

All LDK120C31R 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 LDK120C31R meets industry standards.

7.What is the process for return or replacement of LDK120C31R?

All LDK120C31R units undergo pre-shipment inspection (PSI). If there is an issue with LDK120C31R, 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 LDK120C31R part is unused and in its original packaging.

Return procedure for LDK120C31R:

1.Submit a request within 90 days.

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

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