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STMicroelectronics L4972AD
- Part No.:
- L4972AD
- Manufacturer:
- STMicroelectronics
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
L4972AD.pdf
- Description:
- IC REG BUCK ADJ 2A 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,329
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Product details
Overview
L4972AD from STMicroelectronics is a monolithic stepdown switching regulator IC delivering 2A continuous output current with adjustable output voltage from 5.1V to 40V, operating up to 200kHz switching frequency in continuous conduction mode, featuring internal 5.1V ±2% reference, feed-forward line regulation, and reset/power-fail monitoring for microprocessor systems.
For engineers reviewing the L4972AD datasheet, L4972AD pinout, L4972AD application, or L4972AD equivalent, this device supports high-efficiency DC-DC conversion in industrial power supplies, embedded system rails, and multi-voltage board designs requiring precise undervoltage lockout, soft-start control, and synchronous operation across multiple regulators.
Technical Context
The L4972AD integrates a vertical DMOS power transistor using BCD mixed-signal technology, enabling fast switching (50ns typical) and high efficiency (up to 90% at 2A). Its PWM control loop uses a sawtooth oscillator with feed-forward compensation, error amplifier with external RC compensation (Pin 7), and a latch to prevent multiple pulses per cycle.
It implements diagnostic functions including open-drain reset output (Pin 3) triggered by input voltage threshold (Pin 4, 5.1V reference-based), programmable delay via capacitor on Pin 2, and thermal shutdown at ~150°C with hysteresis. Startup is enabled via internal Vstart circuit (Pin 14) with turn-on threshold of 11V ±1V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 2A continuous - supports medium-power loads without external pass devices |
| Output Voltage Range | 5.1V to 40V - adjustable via external feedback divider; fixed 5.1V when connected directly to FB (Pin 9) |
| Switching Frequency | Up to 200kHz - enables compact LC filter design with reduced size/cost of inductors and capacitors |
| Reference Voltage | 5.1V ±2% (Pin 13) - precision internal bandgap reference used for regulation and power-fail detection |
| Duty Cycle Range | 0–90% - supports wide input-to-output voltage ratios while maintaining stable regulation |
| Efficiency | Up to 90% at Vo = 5.1V, Io = 2A, fsw = 100kHz - achieved via low Rds(on) DMOS and optimized gate drive |
| Thermal Shutdown | ~150°C junction temperature with hysteresis - protects against sustained overload or poor heatsinking |
Pinout & Package
L4972AD is housed in a SO20 (Small Outline, 20-pin) plastic package with exposed thermal pad (per SO20 mechanical drawing), compatible with standard surface-mount reflow processes and offering lower thermal resistance (Rth j-amb max 80°C/W) than DIP variants.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (BOOTSTRAP) | Bootstrap capacitor connection | Charges to ~12V to drive DMOS gate above output voltage; enables high-side N-channel switch operation |
| 2 (RESET DELAY) | Reset timing capacitor node | External capacitor sets delay before reset signal asserts after power-up or recovery |
| 3 (RESET OUT) | Open-collector reset output | Active-low signal indicating valid output voltage and input supply status; sinks up to 50mA |
| 4 (P. FAIL INPUT) | Power-fail threshold input | Compares input voltage (via external divider) to internal 5.1V reference; triggers reset on undervoltage |
| 5,6,15,16 (GND) | Common ground terminals | Multiple GND pins reduce ground impedance and improve noise immunity in high-current switching paths |
| 7 (FREQ. COMP.) | Error amplifier output / compensation node | Connect external RC network to set loop gain, phase margin, and transient response stability |
| 8 (SOFT START) | Soft-start timing capacitor node | Capacitor defines linear ramp time for output voltage rise; prevents inrush current and overshoot |
| 9 (FEEDBACK IN.) | Regulation error sense input | Compares output (direct or divided) to 5.1V reference; primary control point for output voltage accuracy |
| 10 (SYNC INPUT) | External synchronization input | Accepts TTL/CMOS clock to synchronize switching frequency across multiple L4972ADs, reducing EMI |
| 11 (SUPPLY VOLTAGE) | Main unregulated input | Operates from 15V to 50V input range; includes UVLO with 11V turn-on and 1V hysteresis |
| 12,19 (N.C.) | No-connect terminals | Not internally bonded; must remain unconnected to avoid parasitic coupling or latch-up risk |
| 13 (Vref) | Internal 5.1V reference output | Stable, trimmed reference usable for external circuitry; load-limited to 1mA max |
| 14 (Vstart) | Internal start-up voltage source | Provides ~12V to bootstrap circuit during initial power-up; ensures reliable gate drive before regulation |
| 17 (Rosc) | Oscillator timing resistor | External resistor to ground sets constant charging current for Cosc; determines switching frequency |
| 18 (Cosc) | Oscillator timing capacitor | External capacitor to ground, with Rosc, sets switching frequency; supports 20kHz–200kHz range |
| 20 (OUTPUT) | Regulated DC output | DMOS-switched output node; requires external LC filter and catch diode (e.g., STPS5L60) |
Key Features
| Feature | Design Value |
|---|---|
| Integrated DMOS power switch | Enables self-contained buck topology with no external MOSFET required; reduces BOM count and layout complexity |
| Feed-forward line regulation | Improves line transient response and reduces output variation over wide input range (15–50V) |
| PWM latch with single-pulse-per-cycle | Eliminates subharmonic oscillation and noise-induced multiple switching events in noisy environments |
| Reset and power-fail monitoring | Provides microprocessor-ready signals for safe boot sequencing and brownout detection without external comparators |
| Under-voltage lockout with hysteresis | Prevents erratic startup below 10V and ensures stable operation above 11V; avoids oscillatory behavior near threshold |
Applications
| Industrial PLC Power Rails | Embedded Microcontroller Supply |
|---|---|
|
Use Scenario: Providing stable 5.1V or 12V rail for programmable logic controllers in factory automation cabinets with wide-input 24V/48V DC distribution. IC Role / Device Role / Timing Role: Primary stepdown regulator managing load transients from I/O modules and communication interfaces. Use Value: Integrated reset and power-fail outputs ensure deterministic MCU boot and graceful shutdown during input dips. |
Use Scenario: Generating clean 5.1V supply for ARM Cortex-M or PIC microcontrollers in battery-backed IoT edge nodes. IC Role / Device Role / Timing Role: Core power management IC with soft-start and UVLO protecting firmware integrity during cold starts. Use Value: 200kHz operation allows miniature 150µH inductor and low-ESR ceramic output caps, minimizing board area. |
| Multipower Board Systems | Test & Measurement Equipment |
|
Use Scenario: Synchronizing multiple L4972ADs on a single PCB to generate 5.1V, 12V, and 24V rails with interleaved switching. IC Role / Device Role / Timing Role: Master-slave synchronized buck controller coordinating phase to reduce input ripple and EMI peaks. Use Value: Pin 10 SYNC capability eliminates need for external clock generators or complex timing ICs. |
Use Scenario: Delivering regulated 12V/2A output in portable oscilloscope front-end power stages where efficiency and thermal headroom are critical. IC Role / Device Role / Timing Role: High-efficiency switching regulator replacing linear solutions to minimize heat dissipation in sealed enclosures. Use Value: 90% peak efficiency and thermal shutdown protect against ambient temperature drift and prolonged overloads. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar stepdown switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596-ADJ | Lower max output current (3A vs 2A), fixed 150kHz frequency, no sync or reset outputs, no feed-forward line regulation | Lacks integrated power-fail monitoring and synchronization; requires external circuits for reset generation and EMI control | Choose for cost-sensitive, non-critical applications where diagnostics and multi-rail coordination are unnecessary |
| TPS54202D | Higher switching frequency (2.2MHz), integrated MOSFETs, smaller solution size, but only 2A max and narrower input range (4.5–28V) | Not suitable for 40V output or >28V input systems; lacks dedicated reset/power-fail pins and bootstrap architecture | Prefer for space-constrained designs with ≤28V input and no requirement for >5.1V output or system-level fault signaling |
Compared with LM2596-ADJ and TPS54202D, the L4972AD uniquely combines 40V output capability, built-in reset/power-fail signaling, and synchronization-making it optimal for industrial multi-rail systems requiring robust fault handling and coordinated switching.
Availability
L4972AD is available at Aetrix Electronics and suitable for industrial PLC power rails, embedded microcontroller supply, multipower board systems, and test & measurement equipment requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for L4972AD 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 L4972AD belongs to ST's legacy high-voltage switching regulator product line, engineered specifically for ruggedized industrial power conversion where reliability, integrated diagnostics, and wide input/output flexibility are essential.
FAQ
What is the minimum input voltage required for L4972AD to start regulation?
The L4972AD features an under-voltage lockout with a turn-on threshold of 11V (typical), ±1V hysteresis. Regulation begins only when the input voltage at Pin 11 exceeds this threshold, ensuring sufficient headroom for internal bootstrap and gate drive circuits to operate reliably before enabling the power stage.
Can L4972AD generate output voltages higher than 5.1V?
Yes - the L4972AD supports output voltages from 5.1V to 40V using an external resistive divider from output to Pin 9 (FB). The internal 5.1V reference serves as the regulation setpoint; scaling the feedback network proportionally increases the output while preserving accuracy and stability.
How does the RESET OUT pin function during power-down?
The RESET OUT (Pin 3) is an open-drain output that goes low immediately when either the input voltage falls below the power-fail threshold (set via Pin 4) or the output voltage drops below 5V. This provides fast, deterministic reset assertion to halt microprocessor execution before supply collapse.
Is an external catch diode required, and what type is recommended?
Yes - an external Schottky catch diode is mandatory across the inductor (anode to GND, cathode to OUTPUT). ST recommends STPS5L60 (5A, 60V, low VF) per the evaluation board design; its low forward voltage and fast recovery minimize conduction losses and improve efficiency at 2A load.
L4972AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 15V
- Voltage - Input (Max):
- 50V
- Voltage - Output (Min/Fixed):
- 5.1V
- Voltage - Output (Max):
- 40V
- Current - Output:
- 2A
- Frequency - Switching:
- 100kHz ~ 200kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
L4972AD FAQ
1.How can I place an order for L4972AD through Aetrix?
Please submit a Request for Quotation (RFQ) for L4972AD 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 L4972AD reliable?
The price and inventory of L4972AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4972AD is usually 5 days.
3.What payment methods are accepted for L4972AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4972AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L4972AD?
L4972AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L4972AD 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 L4972AD?
For technical support, including L4972AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4972AD requirements.
6.How does Aetrix verify that L4972AD is sourced from the original manufacturer or authorized distributors?
All L4972AD 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 L4972AD meets industry standards.
7.What is the process for return or replacement of L4972AD?
All L4972AD units undergo pre-shipment inspection (PSI). If there is an issue with L4972AD, 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 L4972AD part is unused and in its original packaging.
Return procedure for L4972AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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