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STMicroelectronics L4971D
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- Part No.:
- L4971D
- Manufacturer:
- STMicroelectronics
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
L4971D.pdf
- Description:
- IC REG BUCK ADJ 1.5A 16SO W
- Quantity:
- Payment:
- Shipping:
Inventory:4,829
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Product details
Overview
L4971D from STMicroelectronics is a monolithic step-down switching regulator IC featuring an internal 0.25Ω D-MOS power transistor, delivering up to 1.5A output current with adjustable output voltage from 3.3V to 50V, operating from 8V to 55V input, and supporting switching frequencies up to 300kHz - used in industrial power supplies requiring high-efficiency DC-DC conversion with wide input range.
For engineers reviewing the L4971D datasheet, L4971D pinout, L4971D application, or L4971D equivalent, key selection considerations include its voltage feedforward architecture, ±1% internal 3.3V reference, pulse-by-pulse current limiting, soft-start timing via external capacitor, and thermal shutdown with hiccup-mode short-circuit protection.
Technical Context
The L4971D implements a voltage-mode PWM controller with integrated power switch and bootstrap gate drive for high-side N-channel MOSFET operation. Its voltage feedforward compensation dynamically adjusts oscillator ramp amplitude based on input voltage, improving line regulation and transient response without external loop compensation components.
It features dual-stage overcurrent protection: cycle-by-cycle current limiting during overload and hiccup-mode shutdown under sustained short-circuit conditions. The error amplifier provides 57dB open-loop gain and 2.5mS transconductance, with COMP pin enabling Type II/III compensation network design for stable closed-loop regulation across load and line variations.
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 - enables direct use with 12V/24V/48V industrial bus rails and battery systems |
| Output Voltage Range | 3.3V to 50V (adjustable) - covers logic supply, analog rails, and intermediate bus voltages |
| Switching Frequency | Up to 300kHz - balances efficiency vs. size of external inductor and capacitors |
| Reference Voltage | 3.36V ±1% - ensures tight output regulation accuracy across temperature and load |
| RDS(on) | 0.25Ω typical - minimizes conduction loss and thermal rise at full load |
| Quiescent Current | 6mA operating / 200µA standby - enables low-power sleep mode in battery-backed systems |
Pinout & Package
Available in SO16W surface-mount package (10.1mm × 7.4mm, 1.27mm pitch), optimized for thermal performance in compact power designs. Pin 1 marked by notch or dot; pins 1, 7, 8, 9, 10, 15, and 16 are NC (no internal connection).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 2) | Power and signal ground reference | Common return path for internal bias, feedback, and PWM circuitry; must be low-impedance |
| SS_INH (Pin 3) | Soft-start timing & inhibit control | Capacitor-to-ground sets soft-start ramp time; logic-low disables regulator and reduces IQ to 200µA |
| OSC (Pin 4) | Oscillator frequency setting | Resistor-to-VCC + capacitor-to-ground configures switching frequency and enables automatic voltage feedforward |
| OUT (Pins 5,6) | Power switch output node | Drives external inductor; connects to BOOT capacitor for high-side gate drive bootstrapping |
| VCC (Pin 11) | Unregulated input supply | Primary power source for internal circuitry and gate driver; must be ≥8V and ≤55V |
| BOOT (Pin 12) | Bootstrap gate drive supply | Capacitor between BOOT and OUT generates floating voltage to fully enhance internal DMOS transistor |
| COMP (Pin 13) | Error amplifier output | Connects to external compensation network (RC/Zener) to stabilize feedback loop dynamics |
| FB (Pin 14) | Feedback voltage input | Direct connection yields 3.3V output; resistive divider scales for higher regulated outputs |
Key Features
| Feature | Design Value |
|---|---|
| Voltage feedforward regulation | Eliminates need for complex line-compensation networks; improves line transient response by >50% |
| Pulse-by-pulse current limiting | Prevents MOSFET failure during momentary overloads by clamping each switching cycle's peak current |
| Hiccup-mode short-circuit protection | Shuts down regulator after repeated current-limit events, then auto-restarts - prevents thermal runaway |
| Zero-load operation capability | Maintains regulation down to 0A output current without burst-mode instability or output voltage drift |
| Internal 3.3V ±1% reference | Enables accurate 3.3V LDO replacement or precision adjustable rail generation without external reference |
Applications
| Industrial PLC Power Supply | Telecom Intermediate Bus Converter |
|---|---|
|
Use Scenario: Provides isolated 5.1V/1.5A rail from 24V or 48V backplane in programmable logic controller modules. IC Role / Device Role / Timing Role: Primary step-down regulator controlling power delivery to microcontroller, I/O drivers, and communication interfaces. Use Value: Achieves 86% efficiency at 1.5A/5.1V with <6mV load regulation - eliminates need for secondary LDOs and reduces board heat density. |
Use Scenario: Generates stable 12V intermediate bus from 48V telecom rectified input in base station power distribution units. IC Role / Device Role / Timing Role: High-voltage buck controller managing bulk power conversion before point-of-load regulators. Use Value: Withstands 55V max input and delivers 93% efficiency at 1.5A/12V - extends system uptime during brownout conditions. |
| Automotive Body Control Module | Test Equipment Auxiliary Supply |
|
Use Scenario: Supplies 3.3V/1.5A to MCU and CAN transceivers in 12V vehicle body electronics with cold-crank tolerance. IC Role / Device Role / Timing Role: Input-rail tolerant buck regulator maintaining regulation during 6V–16V battery transients. Use Value: Operates down to 8V input and maintains ±1% output accuracy - avoids MCU reset during engine cranking. |
Use Scenario: Powers analog front-end circuits in portable bench instruments requiring low-noise, adjustable 3.3V–15V rails. IC Role / Device Role / Timing Role: Programmable lab-grade DC-DC source with precise voltage setpoint and soft-start sequencing. Use Value: Adjustable output (3.3V–50V) and 10mV ripple at 1.5A enable clean analog supply without post-regulation filtering. |
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 |
|---|---|---|---|
| LM2596S-ADJ | Fixed 150kHz frequency, no voltage feedforward, 3A rating but larger dropout (1.5V min) | Lacks hiccup-mode protection and zero-load regulation; requires external compensation | Preferred for cost-sensitive, lower-performance 12V→5V/3.3V conversions where input range is narrow |
| TPS54302DDAR | Higher 2.5A rating, 2.5V–28V input, integrated FETs, but no internal 3.3V reference | Requires external reference for 3.3V output; lacks dedicated inhibit pin for ultra-low standby | Better for space-constrained designs needing >1.5A, but adds BOM complexity for precision 3.3V regulation |
Compared with LM2596S-ADJ and TPS54302DDAR, the L4971D uniquely combines wide 8V–55V input, ±1% internal 3.3V reference, hiccup-mode fault recovery, and voltage feedforward - making it optimal for ruggedized industrial and automotive DC-DC stages where reliability and regulation accuracy outweigh raw current headroom.
Availability
L4971D is available at Aetrix Electronics and suitable for industrial PLC power supplies, telecom intermediate bus converters, automotive body control modules, and test equipment auxiliary supplies requiring stable component supply across extended lifecycle programs.
Supply support for L4971D 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, specializing in power management, microcontrollers, and automotive-grade analog ICs.
The L4971D belongs to ST's legacy high-voltage buck regulator product line, designed specifically for industrial and automotive power conversion where wide input range, robust protection, and precision regulation are critical.
FAQ
What is the minimum input voltage required for L4971D to regulate a 3.3V output?
The L4971D requires a minimum input voltage of 8V to maintain regulation at 3.3V output, due to internal circuitry overhead and the 0.55V typical dropout voltage across the internal DMOS transistor at 1.5A. Below 8V, the device enters undervoltage lockout and ceases switching.
Can L4971D operate without an external inductor?
No - the L4971D is a controller-integrated buck converter requiring an external inductor (e.g., 126µH for 100kHz operation) to store and transfer energy. It does not contain magnetic components; omission of the inductor will cause immediate failure due to uncontrolled current surge through the internal DMOS.
How is the soft-start time determined for L4971D?
Soft-start time is set by the capacitor connected between SS_INH (Pin 3) and GND: tSS ≈ CSS × 40µA / (VREF – 0.6V). For example, a 100nF capacitor yields ~1ms soft-start ramp. This linear voltage ramp controls PWM duty cycle startup to limit inrush current into output capacitors.
Does L4971D require external bootstrap diode or capacitor?
Yes - a ceramic bootstrap capacitor (typically 100nF) must be placed between BOOT (Pin 12) and OUT (Pins 5,6); no external diode is needed because the internal charge pump and bootstrapping circuitry are fully integrated and self-commutating during normal operation.
L4971D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- 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:
- Surface Mount
- Supplier Device Package:
- 16-SO W
L4971D FAQ
1.How can I place an order for L4971D through Aetrix?
Please submit a Request for Quotation (RFQ) for L4971D 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 L4971D reliable?
The price and inventory of L4971D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4971D is usually 5 days.
3.What payment methods are accepted for L4971D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4971D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L4971D?
L4971D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L4971D 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 L4971D?
For technical support, including L4971D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4971D requirements.
6.How does Aetrix verify that L4971D is sourced from the original manufacturer or authorized distributors?
All L4971D 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 L4971D meets industry standards.
7.What is the process for return or replacement of L4971D?
All L4971D units undergo pre-shipment inspection (PSI). If there is an issue with L4971D, 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 L4971D part is unused and in its original packaging.
Return procedure for L4971D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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