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

STMicroelectronics L5973D

Name: L5973D
Brand: STMicroelectronics
SKU: L5973D
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L5973D

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

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

Datasheet:: L5973D.pdf

Description:: IC REG BUCK ADJ 2.5A 8HSOP

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Product details

Overview

L5973D from STMicroelectronics is a monolithic step-down switching regulator with an internal 2.5 A P-channel D-MOS switch, 4–36 V input range, adjustable 1.235–35 V output, and fixed 250 kHz switching frequency. It delivers >2 A DC load current in typical applications, supports 100% duty cycle for low-dropout operation, and features voltage feedforward, synchronization, and thermal shutdown-used in LCD monitors, hard disk drives, and automotive infotainment systems.

For engineers reviewing the L5973D datasheet, L5973D pinout, L5973D application, or L5973D equivalent, key selection criteria include its SO8 exposed-pad thermal performance (R_thJA = 40°C/W), ±2% reference accuracy, pulse-by-pulse current limiting, and INH pin for zero-quiescent-current disable-critical for power-sensitive embedded and industrial DC-DC designs.

Technical Context

The L5973D implements a voltage-mode buck topology with internal P-channel MOSFET (R_DS(on) = 250 mΩ typ), fixed-frequency oscillator (250 kHz), and integrated error amplifier with COMP pin for external compensation. Its voltage feedforward architecture improves line regulation and transient response across wide input ranges.

It supports master/slave synchronization via SYNC pin, includes dedicated VREF (3.3 V ±2%) and FB (1.235 V nominal) pins for precise output setting, and integrates protection including thermal shutdown, feedback disconnection detection, and internal current limiting with pulse-by-pulse modulation.

Key Specifications

Parameter	Value and Actual Design Meaning
Input Voltage Range	4 V to 36 V - enables direct use on 5 V, 12 V, and 24 V rails without pre-regulation.
Output Current Capability	2.5 A min switch current limit - supports ≥2 A continuous DC load under thermal design with HSOP8 exposed pad.
Switching Frequency	250 kHz fixed - balances EMI control, inductor size, and efficiency in mid-power DC-DC stages.
Reference Voltage	3.3 V ±2% (VREF), 1.235 V ±1.2% (FB) - enables accurate adjustable outputs with standard resistor dividers.
Thermal Resistance	R_thJA = 40°C/W (HSOP8 exposed pad) - allows >2 W dissipation at T_A ≤ 60°C without forced cooling.
Quiescent Current	3–5 mA operating, 50–150 µA standby (INH high) - suitable for always-on subsystems with low-power sleep modes.
Duty Cycle Range	0–100% - supports ultra-low dropout operation down to V_OUT ≈ V_IN − 0.4 V at full load.

Pinout & Package

Package: HSOP8 with exposed thermal pad (ECOPACK-compliant), 5.0 mm × 6.2 mm footprint, R_thJA = 40°C/W when mounted per datasheet layout guidelines.

Pin/Terminal	Circuit Role	Design Meaning
OUT (Pin 1)	Power switch output node	Connects to inductor and output capacitor; carries high di/dt switching current and must be routed with low-inductance loop.
SYNC (Pin 2)	Synchronization input/output	Accepts external clock (2.5 V logic high) or drives slave devices; enables EMI reduction via frequency alignment.
INH (Pin 3)	Enable/disable control	Active-high logic input; open-circuit defaults to disable via internal pull-up; grounds to enable.
COMP (Pin 4)	Error amplifier output	External compensation network (RC) connects here to set loop bandwidth and phase margin.
FB (Pin 5)	Feedback sensing input	Monitors output via resistive divider; regulates to 1.235 V - sets V_OUT = 1.235 × (1 + R1/R2).
VREF (Pin 6)	Stable 3.3 V reference	Provides precision bias for external circuits; no bypass capacitor required for stability.
GND (Pin 7)	Analog and power ground	Common return for FB, COMP, VREF, and INH; must be tied to exposed pad for thermal and noise integrity.
VCC (Pin 8)	Unregulated input supply	Primary power input (4–36 V); powers internal circuitry and gate driver; decoupling required near pin.

Key Features

Feature	Design Value
Voltage feedforward control	Improves line regulation and transient response without requiring complex compensation adjustments.
Zero-load operation	Maintains regulation with no minimum load requirement - eliminates need for dummy loads in battery-powered systems.
Internal current limiting with pulse-by-pulse modulation	Provides robust short-circuit protection while maintaining stable operation during overload transients.
Inhibit pin with microamp standby current	Reduces total system quiescent current to <150 µA - critical for automotive always-on modules and IoT edge nodes.
Thermal shutdown with hysteresis	Shuts down at ~150°C junction temperature and auto-recovers after cooldown - prevents permanent damage during sustained overloads.

Applications

Hard Disk Drive Power Supply

LCD Monitor Main Rail

Use Scenario: Provides regulated 5 V and 12 V rails from a 19 V adapter in desktop and portable LCD monitors.

IC Role / Device Role / Timing Role: Primary buck controller delivering >2 A at 5 V with tight line/load regulation and low ripple.

Use Value: Enables compact, fanless monitor designs using HSOP8 thermal pad to dissipate >1.5 W without heatsinks.

Use Scenario: Powers logic and backlight drivers in flat-panel displays with variable input from AC/DC adapters.

IC Role / Device Role / Timing Role: Adjustable-output buck regulator configured for 3.3 V or 5 V main logic rail with SYNC for EMI spread-spectrum alignment.

Use Value: Delivers ±2% output accuracy across 4–36 V input and -40°C to +125°C ambient, ensuring display controller stability.

Automotive Infotainment Core Supply

Industrial DC-DC Module

Use Scenario: Generates 3.3 V core voltage for SoC and audio codecs in car radio head units powered from 9–16 V battery.

IC Role / Device Role / Timing Role: High-input-range buck converter with 100% duty cycle capability for cold-crank (6.5 V) support.

Use Value: Maintains regulation during engine start-up dips; INH pin enables controlled power sequencing with MCU GPIO.

Use Scenario: Serves as the main regulator in DIN-rail-mounted programmable logic controllers with 24 V bus input.

IC Role / Device Role / Timing Role: Robust, thermally efficient DC-DC stage delivering 2 A at 5 V or 12 V with built-in thermal and short-circuit protection.

Use Value: HSOP8 exposed pad and 40°C/W R_thJA allow continuous 2 A operation in 70°C cabinet environments without derating.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM2596S-ADJ	3 A switch, 150 kHz fixed frequency, no SYNC or VREF pin, higher R_DS(on) (~350 mΩ)	Lacks voltage feedforward and precision 3.3 V reference; requires larger inductor for same ripple	Prefer for cost-sensitive, non-synchronized, lower-EMI applications where thermal margin is ample
MP2307DN-LF-Z	3 A switch, 340 kHz frequency, no VREF pin, no INH, smaller SOP8 package (no exposed pad)	Higher switching loss and thermal resistance (R_thJA ≈ 65°C/W) limits continuous current to ~1.5 A	Choose when board space is constrained and peak current <1.8 A; avoid for high-ambient or high-duty-cycle use

Compared with LM2596S-ADJ and MP2307DN-LF-Z, the L5973D offers superior thermal performance (40°C/W), integrated 3.3 V reference, synchronization capability, and feedforward control-making it optimal for high-reliability, thermally constrained, or EMI-sensitive industrial and automotive DC-DC stages.

Availability

L5973D is available at Aetrix Electronics and suitable for LCD monitor power supplies, automotive infotainment systems, and industrial DC-DC modules requiring stable component supply, long-lifecycle support, and ECOPACK-compliant packaging.

Supply support for L5973D 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The L5973D belongs to ST's monolithic DC-DC switching regulator product line, engineered for high-current, wide-input-voltage industrial and automotive power conversion with emphasis on thermal efficiency, protection robustness, and design simplicity.

FAQ

What is the maximum continuous output current achievable with the L5973D?

The L5973D guarantees a minimum 2.5 A switch current limit and can deliver >2 A DC output continuously under proper thermal design-specifically with the HSOP8 exposed pad mounted on ≥2 oz copper with thermal vias, achieving R_thJA = 40°C/W. At 12 V_IN/3.3 V_OUT, typical efficiency exceeds 90% up to 2.2 A before thermal limiting begins.

How does the INH pin function, and what is its logic threshold?

The INH pin is an active-high enable input with a guaranteed turn-on threshold of ≥0.8 V and turn-off threshold of ≤2.2 V. When left unconnected, an internal pull-up disables the device; grounding enables operation. In standby mode (INH high), total quiescent current drops to 50–150 µA, making it ideal for battery-backed or always-on subsystems.

Can the L5973D regulate output voltages below 1.235 V?

Yes-using the circuit in Figure 19 of the datasheet, the L5973D can generate outputs as low as 0.6 V by injecting current into the FB pin via an auxiliary resistor network. The formula V_OUT = V_FB − [(V_REF − V_FB) × (R2/R1)] applies, and a minimum load resistor is required to prevent output overvoltage when unloaded.

What is the purpose of the VREF pin, and is external decoupling required?

The VREF pin provides a stable, buffered 3.3 V ±2% reference output usable for external circuit biasing (e.g., ADC references or sensor excitation). Unlike most regulators, no external capacitor is required for stability-the internal design ensures noise immunity and regulation integrity without added components.

L5973D Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Active

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Adjustable

Number of Outputs:: 1

Voltage - Input (Min):: 4V

Voltage - Input (Max):: 36V

Voltage - Output (Min/Fixed):: 1.235V

Voltage - Output (Max):: 35V

Current - Output:: 2.5A

Frequency - Switching:: 250kHz

Synchronous Rectifier:: No

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-HSOP

L5973D FAQ

1.How can I place an order for L5973D through Aetrix?

Please submit a Request for Quotation (RFQ) for L5973D 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 L5973D reliable?

The price and inventory of L5973D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L5973D is usually 5 days.

3.What payment methods are accepted for L5973D?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L5973D transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L5973D?

L5973D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L5973D 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 L5973D?

For technical support, including L5973D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L5973D requirements.

6.How does Aetrix verify that L5973D is sourced from the original manufacturer or authorized distributors?

All L5973D 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 L5973D meets industry standards.

7.What is the process for return or replacement of L5973D?

All L5973D units undergo pre-shipment inspection (PSI). If there is an issue with L5973D, 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 L5973D part is unused and in its original packaging.

Return procedure for L5973D:

1.Submit a request within 90 days.

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

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