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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

STMicroelectronics L4973V3.3

Name: L4973V3.3
Brand: STMicroelectronics
SKU: L4973V3.3
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L4973V3.3

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 18-DIP (0.300", 7.62mm)

Datasheet:: L4973V3.3.pdf

Description:: IC REG BUCK ADJ/0.5V 3.5A 18DIP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L4973V3.3 from STMicroelectronics is a monolithic step-down switching regulator delivering 3.5 A at a fixed 3.3 V ±1% output, operating from 8 V to 55 V input, featuring internal D-MOS with 0.15 Ω R_DS(on), adjustable switching frequency up to 300 kHz, and zero-load quiescent current as low as 1 mA - used in industrial power supplies for distributed 3.3 V rail generation.

For engineers reviewing the L4973V3.3 datasheet, L4973V3.3 pinout, L4973V3.3 application, or L4973V3.3 equivalent, key selection concerns include input voltage range compliance (8–55 V), thermal derating at high ambient temperatures, feedback loop stability with external compensation, and synchronization capability for multi-regulator systems.

Technical Context

The L4973V3.3 integrates a BCD-technology D-MOS power switch and error amplifier with voltage feed-forward control, enabling fast transient response and stable regulation across wide input/output differentials. Its oscillator supports external R/C programming and automatic line feed-forward without additional components.

Protection architecture includes pulse-by-pulse current limiting, hiccup-mode short-circuit recovery, thermal shutdown, output overvoltage protection, and feedback disconnection detection - all implemented in a single SO-20 (12+4+4) package with dedicated BOOT, SYNC, and INH pins for system-level control.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 3.3 V ±1% - ensures reliable logic-level supply for microcontrollers and FPGAs without external divider.
Max output current	3.5 A continuous - supports high-current digital loads such as SoC core rails or multi-channel sensor interfaces.
Input voltage range	8 V to 55 V - accommodates 12 V/24 V/48 V industrial bus systems with margin for transients.
R_DS(on)	0.15 Ω typical - minimizes conduction loss and enables >85% efficiency at 3.3 V/3.5 A output.
Switching frequency	Adjustable up to 300 kHz - balances EMI control, inductor size, and efficiency for compact board layouts.
Quiescent current	2.7–4 mA at no load - enables low-power standby operation in always-on industrial monitoring nodes.
Thermal resistance	R_thJA = 80 °C/W - requires PCB copper area and thermal vias for full 3.5 A operation above 70 °C ambient.

Pinout & Package

Package: SO-20 (12+4+4) surface-mount package with exposed thermal pad (not electrically connected); pin count and layout optimized for high-current buck converter layout with separate power, ground, and signal groups.

Pin/Terminal	Circuit Role	Design Meaning
2,3 OUT	Power output node	High-current path to output capacitor and load; connects directly to internal D-MOS drain.
4,5,6,7,14,15,16,17 GND	Signal and power ground	Eight dedicated ground pins reduce impedance and improve noise immunity for feedback and control loops.
8,9 VCC	Unregulated input supply	Provides bias for internal circuitry; must be decoupled near pin with ≥10 µF low-ESR capacitor.
10 INH	Enable/disable control	Active-high logic input; pulls device into <100 µA standby mode when asserted - enables system-level power sequencing.
11 COMP	Error amplifier output	Connects to external RC network for loop compensation; sets phase margin and transient response.
12 VFB	Feedback input	Internal 3.3 V reference connection point; direct tie yields fixed 3.3 V output; external divider enables adjustable outputs.
13 V5.1	5.1 V reference output	Stable 5.1 V ±1.5% reference available for auxiliary circuits or precision sensing - not used in L4973V3.3 configuration.
18 BOOT	Bootstrap gate drive	Capacitor between BOOT and OUT provides gate drive voltage > V_OUT for internal high-side switch - critical for duty cycle >95%.
20 SYNC	Sync input/output	Allows master-slave synchronization of multiple L4973 regulators to reduce beat-frequency EMI in multi-rail systems.
1 OSC	Oscillator timing	External R-C network sets switching frequency; resistor to VCC and capacitor to GND - determines ripple and filter size.

Key Features

Feature	Design Value
Voltage feed-forward regulation	Compensates for input voltage changes within one switching cycle - eliminates need for complex loop compensation under line transients.
Soft-start function	Internally controlled ramp-up of output voltage via external capacitor - prevents inrush current and overshoot during power-up.
Pulse-by-pulse current limiting	Detects overcurrent on each switching cycle and disables gate drive - protects MOSFET and inductor during short-circuit faults.
Hiccup-mode protection	Enters auto-retry after fault clearance - maintains safe thermal state while allowing recovery without manual reset.
Inhibit with zero-current sleep	Reduces total supply current to ≤200 µA at VCC = 24 V - enables energy-efficient system-level power gating.

Applications

Industrial PLC Power Supply

Automotive Body Control Module

Use Scenario: Generating stable 3.3 V for ARM Cortex-M7 microcontroller and CAN transceivers in programmable logic controllers with 24 V nominal input.

IC Role / Device Role / Timing Role: Primary DC-DC buck regulator providing isolated, low-noise core voltage with thermal robustness for continuous operation in cabinet-mounted enclosures.

Use Value: 8–55 V input range tolerates battery drop and load dump; hiccup-mode protection avoids latch-up during field wiring faults.

Use Scenario: Powering infotainment SoC subsystems (e.g., display interface, audio codec) from vehicle 12 V battery with cold-crank resilience.

IC Role / Device Role / Timing Role: High-efficiency step-down regulator supporting dynamic voltage scaling and low-quiescent operation during ignition-off modes.

Use Value: 2.7 mA no-load current extends battery life in parked state; SYNC pin enables EMI-aligned switching with other onboard converters.

Telecom Remote Radio Unit

Medical Diagnostic Sensor Hub

Use Scenario: Converting 48 V PoE-derived input to 3.3 V for FPGA-based signal processing and RF front-end ICs in outdoor base station radios.

IC Role / Device Role / Timing Role: High-voltage buck controller managing thermal stress in sealed, fanless enclosures with minimal heatsinking.

Use Value: R_DS(on) = 0.15 Ω reduces power loss at full 3.5 A load; thermal shutdown prevents damage during extended high-temperature operation.

Use Scenario: Providing clean, low-noise 3.3 V supply to precision ADCs, analog front-ends, and wireless BLE modules in portable diagnostic devices.

IC Role / Device Role / Timing Role: Regulated power source with soft-start and output overvoltage protection to safeguard sensitive analog measurement circuitry.

Use Value: Fixed 3.3 V ±1% output eliminates calibration drift; feedback disconnection protection prevents unregulated output during sensor cable failure.

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM2596T-3.3	3 A max output, 4.5–40 V input, fixed 3.3 V, no SYNC or INH, R_DS(on) ≈ 0.22 Ω	Lacks hiccup-mode, sync, and precise inhibit - suitable only for non-critical, lower-power applications	Choose if cost sensitivity outweighs thermal performance and system-level control needs.
MP2315GJ-Z	3.5 A, 4.5–36 V input, fixed 3.3 V, 500 kHz f_SW, integrated MOSFETs, no V5.1 reference	Higher switching frequency reduces inductor size but increases EMI filtering complexity; no external sync capability	Prefer for space-constrained designs where 36 V max input suffices and thermal management is less demanding.

Compared with LM2596T-3.3 and MP2315GJ-Z, the L4973V3.3 uniquely supports 55 V input, offers dual-mode current limiting, and provides system-level features like SYNC and INH - making it optimal for ruggedized industrial and automotive power domains requiring wide VIN and robust fault handling.

Availability

L4973V3.3 is available at Aetrix Electronics and suitable for industrial PLCs, automotive body control units, telecom remote radio units, and medical sensor hubs requiring stable component supply across extended temperature and voltage ranges.

Supply support for L4973V3.3 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 power management applications.

The L4973 series belongs to ST's high-voltage DC-DC converter product line, engineered specifically for industrial and transportation systems needing wide-input, high-current, and fault-resilient power conversion in harsh environments.

FAQ

What is the minimum input voltage required for stable 3.3 V output at full 3.5 A load?

The L4973V3.3 requires a minimum input voltage of 8 V to maintain regulated 3.3 V output at 3.5 A, as confirmed by electrical characteristics tables and dropout voltage curves. Below this threshold, the internal D-MOS cannot sustain sufficient gate drive or duty cycle, causing output collapse. Input ripple must also remain within ±0.5 V to avoid line regulation errors exceeding ±1%.

Can the L4973V3.3 be synchronized to an external clock, and what are the voltage thresholds for the SYNC pin?

Yes, the SYNC pin (Pin 20) supports both master and slave operation. As a slave input, it accepts TTL-compatible logic levels: high threshold ≥3.5 V and low threshold ≤0.9 V over the full 8–55 V VCC range. As a master output, it drives ≥4 V at 3 mA sink, enabling direct connection to other L4973 devices without level-shifting.

How does the hiccup-mode protection behave during sustained output short-circuit conditions?

Under sustained short-circuit, the L4973V3.3 enters hiccup mode after initial pulse-by-pulse limiting fails to clear the fault: it disables switching for ~20 ms, then attempts one restart pulse. If overload persists, it repeats the cycle - limiting average power dissipation to <0.5 W and junction temperature to <125 °C, preventing thermal runaway without manual intervention.

Is the V5.1 reference pin used in the L4973V3.3 variant, and what is its accuracy and load capability?

Yes, the V5.1 pin (Pin 18) remains active and functional in the L4973V3.3 variant, delivering a precise 5.1 V ±1.5% reference over –40 °C to +125 °C and 0–20 mA load. It is internally derived from the same bandgap source as the 3.3 V regulator, enabling use as a stable reference for external ADCs, comparators, or auxiliary rails - independent of the main output setting.

L4973V3.3 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 18-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Obsolete

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Adjustable (Fixed)

Number of Outputs:: 1

Voltage - Input (Min):: 8V

Voltage - Input (Max):: 55V

Voltage - Output (Min/Fixed):: 0.5V (3.3V)

Voltage - Output (Max):: 50V

Current - Output:: 3.5A

Frequency - Switching:: 100kHz ~ 300kHz

Synchronous Rectifier:: No

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 18-DIP

L4973V3.3 FAQ

1.How can I place an order for L4973V3.3 through Aetrix?

Please submit a Request for Quotation (RFQ) for L4973V3.3 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 L4973V3.3 reliable?

The price and inventory of L4973V3.3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4973V3.3 is usually 5 days.

3.What payment methods are accepted for L4973V3.3?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4973V3.3 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L4973V3.3?

L4973V3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L4973V3.3 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 L4973V3.3?

For technical support, including L4973V3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4973V3.3 requirements.

6.How does Aetrix verify that L4973V3.3 is sourced from the original manufacturer or authorized distributors?

All L4973V3.3 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 L4973V3.3 meets industry standards.

7.What is the process for return or replacement of L4973V3.3?

All L4973V3.3 units undergo pre-shipment inspection (PSI). If there is an issue with L4973V3.3, 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 L4973V3.3 part is unused and in its original packaging.

Return procedure for L4973V3.3:

1.Submit a request within 90 days.

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

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