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STMicroelectronics L4971
- Part No.:
- L4971
- Manufacturer:
- STMicroelectronics
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
L4971.pdf
- Description:
- IC REG BUCK ADJ 1.5A 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,117
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Product details
Overview
L4971 from STMicroelectronics is a monolithic step-down switching regulator IC delivering up to 1.5A output current with adjustable output voltage from 3.3V to 50V, operating from 8V to 55V input, featuring internal 3.3V ±1% reference, 100kHz typical switching frequency, and integrated D-MOS power transistor with 0.25Ω typical RDS(on). It serves as the primary DC-DC conversion stage in industrial power supplies requiring wide-input, high-efficiency regulation.
For engineers reviewing the L4971 datasheet, L4971 pinout, L4971 application, or L4971 equivalent, this device is selected for fixed/adjustable buck conversion where input voltage exceeds 8V, output load reaches 1.5A, thermal management is constrained, and feedback disconnection protection is required in harsh environments.
Technical Context
The L4971 implements voltage-mode PWM control with feedforward compensation, using an internal error amplifier (57dB open-loop gain, 2.5mS transconductance) and oscillator synchronized to external R-C network. Its bootstrap gate drive enables high-side N-channel DMOS switching without external high-voltage bias.
Protection architecture includes cycle-by-cycle current limiting (2.5A typ), hiccup-mode short-circuit response, thermal shutdown at 150°C, and dedicated feedback disconnect detection that forces shutdown if FB pin floats. Inhibit logic supports zero-quiescent-current sleep mode (<200µA standby).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output current | 1.5A continuous - supports mid-power industrial loads without external pass devices |
| Input voltage range | 8V to 55V - accommodates 12V/24V/48V nominal bus systems with wide transient tolerance |
| Output voltage range | 3.3V to 50V adjustable - covers standard logic rails (3.3V, 5.1V), analog supplies (±12V, ±15V), and higher-voltage subsystems |
| Switching frequency | Up to 300kHz - enables compact magnetics while maintaining >85% efficiency at 3.3V/1.5A |
| Reference voltage | 3.3V ±1% - ensures tight output regulation stability across temperature (0.4mV/°C drift) |
| RDS(on) | 0.25Ω typical - minimizes conduction loss in internal power switch, reducing thermal stress on DIP8/SO16W packages |
| Quiescent current | 6mA operating / 200µA standby - enables low-power operation during system idle states |
Pinout & Package
Available in plastic DIP8 (through-hole) and SO16W (wide-body surface-mount) packages. DIP8 meets JEDEC MS-001, SO16W conforms to JEDEC MO-153 with 1.27mm pitch and 10.5mm body width.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (DIP8 Pin 2 / SO16W Pin 3) | Power and signal reference ground | Common return path for internal bias, error amp, and PWM logic; requires low-impedance PCB plane connection |
| SS_INH (DIP8 Pin 3 / SO16W Pin 4) | Soft-start timing and inhibit control | Capacitor-to-ground sets soft-start ramp time; logic-low disables regulator and reduces IQ to <200µA |
| OSC (DIP8 Pin 4 / SO16W Pin 5) | Oscillator timing node | External R-C network sets switching frequency; line feedforward is automatic and requires no additional components |
| OUT (DIP8 Pins 5–6 / SO16W Pins 11–12) | Power switch output | Drives external inductor; dual pins reduce current density and parasitic inductance in high-current paths |
| VCC (DIP8 Pin 11 / SO16W Pin 12) | Unregulated input supply | Provides bias for internal circuitry; must be decoupled locally with ≥100nF ceramic capacitor |
| BOOT (DIP8 Pin 12 / SO16W Pin 13) | Bootstrap gate drive supply | Capacitor between BOOT and OUT generates floating voltage to fully enhance internal DMOS gate above source potential |
| COMP (DIP8 Pin 13 / SO16W Pin 14) | Error amplifier output | Connects to external RC compensation network to stabilize loop response and prevent oscillation |
| FB (DIP8 Pin 14 / SO16W Pin 15) | Feedback input | Direct connection yields 3.3V output; resistive divider scales higher outputs with 3.36V nominal reference point |
Key Features
| Feature | Design Value |
|---|---|
| Voltage feedforward regulation | Compensates for input line variations in real time without requiring additional sensing circuitry or loop redesign |
| Pulse-by-pulse current limiting | Clamps peak switch current per cycle to ~2.5A, preventing magnetic saturation and enabling safe restart after overload |
| Hiccup-mode short-circuit protection | Enters burst-mode shutdown on sustained overcurrent, reducing average power dissipation and enabling self-recovery |
| Zero-load operation capability | Maintains regulation down to 0A output with stable 3.3V reference and minimal dropout (0.55V at 1.5A) |
| Thermal shutdown with hysteresis | Shuts down at 150°C junction temperature and resumes only after cooling to ~135°C, preventing thermal runaway |
Applications
| Industrial PLC Power Rails | Telecom Line Card Supplies |
|---|---|
|
Use Scenario: Generating isolated 5.1V/1.5A rails for microcontroller and I/O interface circuits in programmable logic controllers operating from 24V or 48V backplanes. IC Role / Device Role / Timing Role: Primary non-isolated buck converter providing regulated intermediate voltage before downstream LDOs or isolated DC-DC stages. Use Value: Delivers 86% efficiency at 5.1V/1.5A with 10mV ripple, eliminating need for heatsinking in confined DIN-rail enclosures. |
Use Scenario: Supplying 12V/1.5A to analog front-end circuitry and digital signal processors in telecom line cards powered from -48V telecom rectified bus. IC Role / Device Role / Timing Role: High-input-voltage buck regulator converting -48V-derived +55V intermediate rail to stable 12V system supply. Use Value: Supports 55V max input rating and withstands 14V transients per GR-1089, ensuring reliability in central office environments. |
| Automotive Body Control Modules | Test Equipment Auxiliary Supplies |
|
Use Scenario: Providing 3.3V/1.5A for CAN controller, EEPROM, and sensor interfaces in 12V automotive body control modules exposed to load-dump transients. IC Role / Device Role / Timing Role: Main buck regulator handling battery-supplied input (8–16V nominal, up to 55V during load dump) with built-in overvoltage protection. Use Value: Internal 3.3V ±1% reference and 3mV line regulation ensure accurate ADC reference and stable MCU core voltage under battery fluctuations. |
Use Scenario: Delivering adjustable 15V/1.5A output for op-amp biasing and DAC reference in portable benchtop test equipment powered from universal AC adapters. IC Role / Device Role / Timing Role: Programmable-output buck regulator supporting multiple instrument configurations via resistor-divider selection. Use Value: Output adjustability from 3.3V to 50V allows single BOM variant to serve diverse analog subsystems, reducing inventory complexity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596-ADJ | Lower max input (40V), lower current (3A), no internal DMOS (external switch required), no feedforward | Requires external MOSFET and driver; lacks hiccup-mode protection and feedback disconnect detection | Choose when cost sensitivity outweighs protection robustness and input voltage stays below 40V |
| TPS5430 | Higher switching frequency (up to 500kHz), lower quiescent current (3.5mA), but narrower input (5.5–36V) | Not suitable for 48V+ systems; requires external bootstrap diode; lacks zero-load regulation guarantee | Prefer for space-constrained designs needing >300kHz operation and 24V-only inputs |
Compared with LM2596-ADJ and TPS5430, the L4971 uniquely combines 55V input tolerance, integrated DMOS, hiccup-mode fault recovery, and guaranteed zero-load regulation-making it optimal for ruggedized industrial and automotive 48V-system power stages where reliability trumps raw frequency or ultra-low IQ.
Availability
L4971 is available at Aetrix Electronics and suitable for industrial PLCs, telecom line cards, automotive body control modules, and test equipment requiring stable component supply across extended temperature and voltage ranges.
Supply support for L4971 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 L4971 belongs to ST's legacy power management IC portfolio targeting high-reliability DC-DC conversion in harsh environments, emphasizing wide-input operation, integrated protection, and thermal resilience over ultra-high-frequency optimization.
FAQ
What package variants are offered for the L4971?
The L4971 is manufactured in two industry-standard packages: DIP8 (dual in-line, through-hole) and SO16W (16-pin wide-body SOIC surface-mount). The SO16W variant uses a 1.27mm lead pitch and 10.5mm body width per JEDEC MO-153, while DIP8 complies with JEDEC MS-001. Both packages share identical electrical specifications and pin functions.
Does the L4971 require an external bootstrap diode?
No. The L4971 integrates a charge pump circuit that automatically charges the BOOT capacitor from the OUT node during low-side conduction, eliminating the need for an external bootstrap diode. This simplifies layout and improves reliability compared to controllers requiring discrete bootstrap networks.
How is output voltage set when using the L4971?
Output voltage is set by connecting the FB pin to a resistive divider between OUT and GND. With no external divider, FB tied directly to OUT yields 3.3V output. For higher voltages, use R1 (from OUT to FB) and R2 (from FB to GND); VOUT = 3.36V × (1 + R1/R2). Typical values for 5.1V are R1 = 20kΩ, R2 = 9.1kΩ.
What thermal derating applies to the L4971 in SO16W package?
In SO16W, the L4971 has a maximum power dissipation of 0.8W at Tamb ≤60°C, with thermal resistance Rth(j-amb) = 110°C/W. Derating begins above 60°C ambient: power limit decreases linearly to zero at 150°C junction temperature. A 2-layer PCB with ≥1in² copper pour under the package reduces effective θJA by ~30%.
L4971 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 8V
- Voltage - Input (Max):
- 55V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- 50V
- Current - Output:
- 1.5A
- Frequency - Switching:
- 100kHz ~ 300kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-DIP
L4971 FAQ
1.How can I place an order for L4971 through Aetrix?
Please submit a Request for Quotation (RFQ) for L4971 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 L4971 reliable?
The price and inventory of L4971 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4971 is usually 5 days.
3.What payment methods are accepted for L4971?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4971 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L4971?
L4971 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L4971 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 L4971?
For technical support, including L4971 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4971 requirements.
6.How does Aetrix verify that L4971 is sourced from the original manufacturer or authorized distributors?
All L4971 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 L4971 meets industry standards.
7.What is the process for return or replacement of L4971?
All L4971 units undergo pre-shipment inspection (PSI). If there is an issue with L4971, 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 L4971 part is unused and in its original packaging.
Return procedure for L4971:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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