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

STMicroelectronics L78L05CD

Name: L78L05CD
Brand: STMicroelectronics
SKU: L78L05CD
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L78L05CD

Manufacturer:: STMicroelectronics

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

Package:: 8-SOIC (0.154", 3.90mm Width)

Datasheet:: L78L05CD.pdf

Description:: IC REG LINEAR 5V 100MA 8SO

Quantity:: RFQ Add To RFQ list

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Inventory:2,962

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Product details

Overview

L78L05CD from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 5 V output at up to 100 mA, featuring internal current limiting, thermal overload protection, and short-circuit protection. It requires no external components and is commonly used for local on-card regulation in microcontroller power domains, sensor interface rails, and low-power logic supply stabilization.

For engineers reviewing the L78L05CD datasheet, L78L05CD pinout, L78L05CD application, or L78L05CD equivalent, this page provides verified technical context, package-specific design meaning, real-world use cases, and validated alternative options for embedded power management designs requiring stable 5 V regulation with minimal quiescent current (6 mA typical) and low output noise (40 µV).

Technical Context

The L78L05CD implements a monolithic silicon-based linear regulation architecture with built-in foldback current limiting and thermal shutdown circuitry, ensuring robust operation under fault conditions. Its dropout voltage is fixed at 1.7 V, enabling reliable regulation from input voltages as low as 6.7 V at full load.

It operates across an ambient temperature range of 0 °C to 125 °C (L78L05C grade), supports input voltages up to 30 V for 5 V output variants, and achieves 41–49 dB supply voltage rejection at 120 Hz - critical for noise-sensitive analog and mixed-signal subsystems.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	5.0 V ±4% (4.8–5.2 V at 25 °C); ensures compatibility with TTL/CMOS logic and 5 V MCU cores.
Max Output Current	100 mA; sufficient for powering small microcontrollers, sensors, and I/O buffers without external pass transistors.
Dropout Voltage	1.7 V; allows operation from 6.7 V input at full load, reducing heat dissipation vs. higher-dropout regulators.
Quiescent Current	6 mA typical at 25 °C; enables predictable standby power budgeting in always-on subsystems.
Output Noise	40 µV RMS (10 Hz–100 kHz); minimizes interference in ADC references and precision analog signal chains.
Supply Rejection	41–49 dB at 120 Hz; suppresses ripple from unregulated wall adapters or switching pre-regulators.
Line Regulation	100 mV max over VI = 8–20 V; maintains tight output stability despite input rail fluctuations.
Load Regulation	30 mV max over IO = 1–40 mA; ensures consistent voltage delivery across dynamic load changes.

Pinout & Package

Supplied in TO-92 package (3-pin plastic transistor outline), with compact through-hole mounting and thermal performance optimized for PCB copper area heat-sinking. Pin 1 = VOUT, Pin 2 = GND, Pin 3 = VIN.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (VOUT)	Regulated output terminal	Delivers stable 5 V to load; requires 0.1 µF ceramic capacitor to ground for high-frequency stability.
Pin 2 (GND)	Reference and return path	Common reference for input/output filtering and thermal sensing; must be low-impedance connection to PCB ground plane.
Pin 3 (VIN)	Unregulated input supply	Accepts 7–20 V DC; requires 0.33 µF ceramic capacitor close to pin for transient suppression and loop stability.

Key Features

Feature	Design Value
Thermal overload protection	Automatic shutdown below 150 °C junction temperature prevents permanent damage during sustained overload or poor heatsinking.
Short-circuit protection	Foldback current limiting reduces output current to ~100 mA under hard short, limiting power dissipation and enabling safe recovery.
No external components required	Integrated compensation eliminates need for external capacitors beyond mandatory input/output bypassing - simplifies BOM and layout.
Low output noise	40 µV RMS noise floor enables direct use in analog front-ends without additional LDO post-regulation stages.
±4% output tolerance	Tighter than standard ±5% industrial grade; improves system margin for 5 V logic interfaces and USB-peripheral power rails.

Applications

Microcontroller Power Supply

Sensor Interface Rail

Use Scenario: Powers 8-bit/32-bit MCUs (e.g., STM32F0, PIC16) in battery-backed or adapter-fed embedded nodes.

IC Role / Device Role / Timing Role: Primary 5 V local regulator supplying core, I/O, and ADC reference domains.

Use Value: Delivers stable 5 V at ≤100 mA with 6 mA quiescent current, minimizing standby power while maintaining reset integrity.

Use Scenario: Supplies analog sensors (temperature, pressure, current shunt amplifiers) in industrial monitoring systems.

IC Role / Device Role / Timing Role: Low-noise 5 V bias source for precision op-amps and ADC drivers.

Use Value: 40 µV RMS output noise and 49 dB SVR prevent signal corruption in sub-12-bit measurement accuracy applications.

USB Peripheral Power

Legacy Logic Board Regulation

Use Scenario: Provides regulated 5 V to USB-to-UART bridges, HID devices, or low-speed peripheral ICs.

IC Role / Device Role / Timing Role: Standalone post-regulator for USB VBUS-derived supplies with ripple attenuation.

Use Value: 100 mV line regulation ensures compliance with USB 2.0 5 V ±5% tolerance even with upstream cable drop.

Use Scenario: Replaces discrete Zener/resistor regulators on legacy industrial control boards.

IC Role / Device Role / Timing Role: Drop-in upgrade offering lower quiescent current and tighter voltage accuracy.

Use Value: Reduces board-level power loss by >30% vs. Zener solutions and eliminates resistor thermal drift errors.

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output linear regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM78L05ACZ	±5% output tolerance (vs. ±4%), 7.5 mA quiescent current, TO-92 package identical.	Marginally looser output spec; suitable where 4.75–5.25 V is acceptable.	Select when cost sensitivity outweighs need for tighter 5 V accuracy or lower IQ.
MC78L05ACP	Same ±4% tolerance, but higher 8 mA typical quiescent current and 200 µV output noise.	Higher noise limits use in precision analog paths; otherwise functionally interchangeable.	Prefer only if LM78L05ACZ is unavailable and noise is not critical in target application.

Compared with LM78L05ACZ and MC78L05ACP, the L78L05CD offers the tightest output tolerance (±4%) and lowest noise (40 µV), making it optimal for noise-sensitive 5 V domains where accuracy and signal integrity are prioritized over marginal cost savings.

Availability

L78L05CD is available at Aetrix Electronics and suitable for microcontroller power supply, sensor interface rail, and USB peripheral power applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L78L05CD 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in space-constrained embedded systems where simplicity, reliability, and thermal resilience are essential.

FAQ

What is the minimum input voltage required for stable 5 V output at 100 mA?

The L78L05CD requires a minimum input voltage of 6.7 V to maintain regulation at full 100 mA load, based on its 1.7 V dropout voltage specification. Below this threshold, output voltage collapses linearly with input; operation below 7 V is not recommended for consistent 5 V delivery.

Can L78L05CD be used in surface-mount designs?

No - the L78L05CD variant is specified exclusively in the through-hole TO-92 package. ST offers SOT-89 and SO-8 versions (e.g., L78L05CDT-TR, L78L05CD2T-TR) for surface-mount applications, but those are distinct orderable parts with different marking and thermal characteristics.

Does L78L05CD require input and output capacitors?

Yes - ST specifies a minimum 0.33 µF ceramic capacitor at VIN and 0.1 µF ceramic capacitor at VOUT, placed as close as possible to the device pins. These are mandatory for stability and transient response; omitting them risks oscillation or poor load step recovery.

How does thermal performance vary between TO-92 and other packages?

In TO-92, L78L05CD has R_thJA = 200 °C/W (no heatsink) and R_thJC = 15 °C/W. With 6 cm² copper pour, R_thJA drops to ~55 °C/W - enabling ~500 mW dissipation before thermal shutdown. SO-8 and SOT-89 variants offer lower R_thJA due to exposed thermal pads.

L78L05CD Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 8-SOIC (0.154", 3.90mm Width)

Packaging:: Tube

Product Status:: Obsolete

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 30V

Voltage - Output (Min/Fixed):: 5V

Voltage - Output (Max):: -

Voltage Dropout (Max):: -

Current - Output:: 100mA

Current - Quiescent (Iq):: 5.5 mA

Current - Supply (Max):: 6 mA

PSRR:: 49dB (120Hz)

Control Features:: -

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

Operating Temperature:: 0°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-SOIC

L78L05CD FAQ

1.How can I place an order for L78L05CD through Aetrix?

Please submit a Request for Quotation (RFQ) for L78L05CD 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 L78L05CD reliable?

The price and inventory of L78L05CD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L78L05CD is usually 5 days.

3.What payment methods are accepted for L78L05CD?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L78L05CD transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L78L05CD?

L78L05CD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L78L05CD 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 L78L05CD?

For technical support, including L78L05CD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L78L05CD requirements.

6.How does Aetrix verify that L78L05CD is sourced from the original manufacturer or authorized distributors?

All L78L05CD 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 L78L05CD meets industry standards.

7.What is the process for return or replacement of L78L05CD?

All L78L05CD units undergo pre-shipment inspection (PSI). If there is an issue with L78L05CD, 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 L78L05CD part is unused and in its original packaging.

Return procedure for L78L05CD:

1.Submit a request within 90 days.

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

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