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

STMicroelectronics L5973AD

Name: L5973AD
Brand: STMicroelectronics
SKU: L5973AD
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L5973AD

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

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

Datasheet:: L5973AD.pdf

Description:: IC REG BUCK ADJ 2A 8HSOP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L5973AD from STMicroelectronics is a monolithic step-down switching regulator with an integrated 2 A P-channel D-MOS power switch, operating from 4 V to 36 V input and delivering adjustable output voltage from 1.235 V to 35 V. It features 500 kHz fixed-frequency operation, 3.3 V ±2% internal reference, voltage feedforward control, and thermal shutdown-enabling compact, high-efficiency DC-DC conversion in space-constrained industrial and consumer power supplies.

For engineers reviewing the L5973AD datasheet, L5973AD pinout, L5973AD application, or L5973AD equivalent, key selection considerations include its HSOP8 exposed-pad thermal performance (R_thJA ≈ 40 °C/W), pulse-by-pulse current limiting (2–3.5 A), zero-load burst-mode operation, and synchronization capability for multi-rail systems.

Technical Context

The L5973AD implements a voltage-mode PWM architecture with an internal transconductance error amplifier (2.3 mS g_m, 50–57 dB open-loop gain) referenced to a precision 1.235 V feedback threshold. Its oscillator generates a fixed 500 kHz sawtooth ramp, enabling voltage feedforward compensation to improve line regulation and transient response.

Current protection combines cycle-by-cycle limiting (triggered at ~2 A) with frequency foldback during overloads, while thermal shutdown activates at 150 °C with ~20 °C hysteresis. The inhibit function supports <100 μA standby current via active-high INH control, and feedback disconnection protection disables the device if FB floats.

Key Specifications

Parameter	Value and Actual Design Meaning
Input Voltage Range	4 V to 36 V - supports 5 V bus and automotive battery inputs without external pre-regulation.
Output Voltage Range	1.235 V to 35 V - set via external resistor divider; 1.235 V achieved by direct FB-to-VOUT connection.
Switch Current Limit	2 A typical, 3.5 A max - enables ≥1.5 A continuous load current with proper thermal design.
Switching Frequency	500 kHz fixed - minimizes external inductor/capacitor size; synchronizable to external clock >500 kHz.
R_DS(on)	0.25 Ω typical - low conduction loss enables high efficiency (90% at 5 V/12 V) without bootstrap circuitry.
Reference Voltage	3.3 V ±2% - stable, unfiltered internal reference available on VREF pin for auxiliary circuitry.
Thermal Resistance	R_thJA = 40 °C/W - enabled by HSOP8 exposed pad; allows >1.5 A operation at +60 °C ambient.

Pinout & Package

Package: HSOP8 with exposed thermal pad (JEDEC MO-187 variant), optimized for low R_thJA and high-power density mounting.

Pin/Terminal	Circuit Role	Design Meaning
1 OUT	Power switch drain output	Connects directly to inductor; carries full switched current; requires low-inductance layout to minimize ringing.
2 SYNC	Synchronization I/O	Configurable as master (output sync signal) or slave (accepts external >500 kHz clock); enables phase-aligned multi-regulator designs.
3 INH	Inhibit control input	Active-high logic: >2.2 V disables regulator (<100 μA I_qst-by); <0.8 V enables; floating defaults to OFF via internal pull-up.
4 COMP	Error amplifier output	Drives external RC compensation network; sets loop stability, bandwidth, and transient response.
5 FB	Feedback input	High-impedance node sensing output voltage via resistor divider; triggers OVP if disconnected or open.
6 VREF	3.3 V reference output	Stable, buffered reference usable for ADC references or biasing; no external capacitor required.
7 GND	Analog/digital ground	Common return for feedback, reference, and control circuits; must be tied to power ground near exposed pad.
8 VCC	Unregulated input supply	Power source for internal circuitry; bypass with 10 μF ceramic close to pin; supports 4–36 V range.

Key Features

Feature	Design Value
Voltage feedforward control	Improves line regulation and transient response by scaling PWM ramp amplitude with V_IN.
Pulse-by-pulse current limiting	Prevents MOSFET destruction during short-circuit by disabling switch each cycle exceeding ~2 A.
Zero-load burst-mode operation	Maintains regulation at no load using P-channel switch - eliminates need for bootstrap capacitor or external bias.
Feedback disconnection protection	Shuts down regulator if FB pin floats, preventing uncontrolled high-duty-cycle output voltage rise.
Thermal shutdown with hysteresis	Turns off power stage at 150 °C junction temperature; restarts only after cooling to ~130 °C to avoid oscillation.

Applications

Consumer Audio Power Supply

Industrial DC-DC Converter

Use Scenario: Powering analog audio stages and DACs in high-fidelity car radios and LCD monitors requiring low-noise, stable 3.3 V or 5 V rails.

IC Role / Device Role / Timing Role: Primary buck regulator delivering regulated output with <±2% accuracy and <10 mV load/line regulation.

Use Value: Integrated 3.3 V reference and feedforward enable tight regulation across wide input (9–16 V automotive) and load (0–1.5 A) ranges.

Use Scenario: Generating isolated or non-isolated 12 V/1.2 A outputs in industrial chargers and battery management systems.

IC Role / Device Role / Timing Role: High-current step-down controller driving external inductor and Schottky diode in standard buck topology.

Use Value: 2 A internal switch and 40 °C/W thermal resistance allow full-rated output without heatsink at +60 °C ambient.

Networking XDSL Line Card

Computer Peripheral Power

Use Scenario: Providing clean 3.3 V and 5 V supplies for DSL modems and line interface ICs in telecom equipment.

IC Role / Device Role / Timing Role: Synchronized buck converter sharing clock with other regulators to reduce EMI peaks in dense PCB layouts.

Use Value: SYNC pin enables deterministic multi-rail timing, minimizing beat frequencies and improving conducted emission compliance.

Use Scenario: Powering USB audio interfaces, graphics card auxiliary rails, and optical drive controllers in desktop PCs.

IC Role / Device Role / Timing Role: Compact, efficient point-of-load regulator replacing linear solutions to reduce heat and board area.

Use Value: 500 kHz switching and SO8 footprint enable small 15 μH inductors and minimal ceramic output capacitance (330 μF POSCAP).

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
L5972D	Same 2 A switch but 250 kHz fixed frequency; higher R_DS(on) (0.3 Ω typ); no SYNC pin.	Lacks synchronization and feedforward; lower switching frequency increases inductor size but reduces EMI.	Select when cost sensitivity outweighs EMI or board space constraints; not suitable for synchronized multi-rail systems.
L5973D	2.5 A switch, same package; identical 500 kHz, SYNC, and features-but higher current limit and slightly higher R_DS(on) (0.22 Ω typ).	Supports higher output current (up to ~1.8 A continuous) with same thermal footprint and feature set.	Choose when future-proofing for higher load or margin is required; pin-compatible upgrade path with identical layout.

Compared with L5972D, the L5973AD offers superior EMI control and smaller magnetics via 500 kHz operation and feedforward; versus L5973D, it trades 0.5 A current headroom for tighter R_DS(on) tolerance and proven thermal margin at 1.5 A loads.

Availability

L5973AD is available at Aetrix Electronics and suitable for industrial DC-DC converters, consumer audio power supplies, and networking XDSL line cards requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L5973AD 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, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The L5973AD belongs to the L597x family of monolithic step-down regulators engineered for high-current, wide-input industrial and automotive power conversion - emphasizing thermal robustness, protection integrity, and layout simplicity.

FAQ

What is the minimum input voltage required for L5973AD to regulate a 3.3 V output?

The L5973AD operates down to 4 V input, making it fully functional for 3.3 V output generation even with marginal 5 V bus conditions. Its 100% duty-cycle capability ensures regulation at V_IN = V_OUT + dropout, and the internal P-channel switch eliminates bootstrap dependency - enabling reliable start-up and regulation at the 4 V absolute minimum rating.

Can L5973AD operate with no output load?

Yes - the L5973AD supports true zero-load operation using burst-mode control. Because it employs a P-channel high-side switch, no bootstrap capacitor is needed, and the internal circuitry maintains regulation even at 0 A output current. Efficiency drops at light loads, but output voltage remains within specification and protection functions remain active.

How does the SYNC pin function in master vs. slave configuration?

When left open, the SYNC pin outputs a signal synchronous with the internal switch turn-off. When driven by an external clock >500 kHz, it forces the L5973AD into slave mode. Connecting SYNC pins of multiple devices causes the highest-frequency unit to act as master; others synchronize as slaves - enabling deterministic interleaving and EMI reduction without external timing ICs.

What thermal derating applies above 60 °C ambient?

The L5973AD's maximum power dissipation is specified at T_A ≤ 60 °C (2.25 W). Above this, derating follows R_thJA ≈ 40 °C/W: for example, at 85 °C ambient, max allowable power drops to ~1.6 W, limiting continuous output current to ~1.2 A at 12 V input/3.3 V output. Layout with full exposed-pad soldering is mandatory to achieve rated thermal performance.

L5973AD 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:: 2A

Frequency - Switching:: 500kHz

Synchronous Rectifier:: No

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-HSOP

L5973AD FAQ

1.How can I place an order for L5973AD through Aetrix?

Please submit a Request for Quotation (RFQ) for L5973AD 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 L5973AD reliable?

The price and inventory of L5973AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L5973AD is usually 5 days.

3.What payment methods are accepted for L5973AD?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L5973AD transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L5973AD?

L5973AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L5973AD 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 L5973AD?

For technical support, including L5973AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L5973AD requirements.

6.How does Aetrix verify that L5973AD is sourced from the original manufacturer or authorized distributors?

All L5973AD 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 L5973AD meets industry standards.

7.What is the process for return or replacement of L5973AD?

All L5973AD units undergo pre-shipment inspection (PSI). If there is an issue with L5973AD, 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 L5973AD part is unused and in its original packaging.

Return procedure for L5973AD:

1.Submit a request within 90 days.

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

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