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STMicroelectronics L6981N33DR
- Part No.:
- L6981N33DR
- Manufacturer:
- STMicroelectronics
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
L6981N33DR.pdf
- Description:
- IC REG BUCK 3.3V 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,501
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Product details
Overview
L6981N33DR from STMicroelectronics is a synchronous step-down DC-DC converter delivering 1.5 A output current with fixed 3.3 V output, operating from 3.5 V to 38 V input. It features 20 µA quiescent current in LCM mode, internal compensation, and SO8 package-designed for industrial 24 V bus systems requiring stable low-noise or high-efficiency regulation.
For engineers reviewing the L6981N33DR datasheet, L6981N33DR pinout, L6981N33DR application, or L6981N33DR equivalent, key selection criteria include light-load efficiency mode (LCM vs LNM), EN/CLKIN dual-function pin behavior, VOUT/FB pin configuration for fixed-output operation, and thermal shutdown at 165 °C with 30 °C hysteresis.
Technical Context
The L6981N33DR implements peak current mode control with internal slope compensation and a transconductance error amplifier. Its fixed 3.3 V output is sensed via internal resistor divider on the VOUT/FB pin, eliminating external feedback components.
It supports two operational modes: Low Consumption Mode (LCM) for battery-powered applications with pulse-skipping at light loads, and Low Noise Mode (LNM) for constant-frequency PWM operation-though L6981N33DR is an LCM variant, confirmed by part number suffix 'N' and 1–6 µA IQ_VIN specification.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.5 V to 38 V - supports direct connection to 24 V industrial buses and wide-range battery inputs without pre-regulation. |
| Output Voltage | Fixed 3.3 V ±1% - internally trimmed reference enables plug-and-play design without external resistors. |
| Max Output Current | 1.5 A DC - sufficient for powering microcontrollers, sensors, and communication interfaces in decentralized nodes. |
| Quiescent Current (IQ) | 1–6 µA from VIN - enables multi-year operation in always-on sensor nodes powered by 24 V batteries. |
| Switching Frequency | 360–440 kHz - balances EMI performance and inductor size; not synchronizable (LCM version). |
| Shutdown Current | 2 µA - ensures minimal leakage during system sleep states, critical for energy harvesting and low-power IoT. |
| Thermal Shutdown | 165 °C with 30 °C hysteresis - protects against sustained overload or poor PCB thermal design without latch-up. |
Pinout & Package
Supplied in SO8 package (SO-8 narrow, 150 mil width), with exposed pad for thermal enhancement. Pin layout optimized for compact buck layout with minimal loop area between VIN, PGND, SW, and BOOT.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 SW | Switching node | Connects to inductor and diode/capacitor node; high dv/dt path requiring tight layout to minimize EMI. |
| 2 BOOT | Bootstrap supply | Requires 100 nF ceramic capacitor to SW; enables high-side NMOS gate drive above VIN. |
| 3 VCC | Analog supply rail | Powers internal bandgap, error amp, and logic; requires ≥1 µF ceramic bypass to AGND. |
| 4 VOUT/FB | Fixed output voltage sense | Internally connected to 3.3 V divider; no external resistors needed-simplifies BOM and layout. |
| 5 EN/CLKIN | Enable input (LCM only) | Digital enable with 1.2 V rising threshold; not used for clock sync (LNM feature only). |
| 6 AGND | Analog ground reference | Separate from PGND to avoid noise coupling into error amplifier; must connect to star ground point. |
| 7 VIN | Main power input | Accepts 3.5–38 V; requires local 10 µF ceramic input capacitor near pin for transient suppression. |
| 8 PGND | Power ground return | High-current return path for HS/LS switches and inductor; ties to thermal pad for heat dissipation. |
Key Features
| Feature | Design Value |
|---|---|
| Internal compensation network | Eliminates need for external Type-II/III compensation components-reduces design time and board space. |
| Programmable soft-start | 1.3 ms internal ramp limits inrush current during power-up, preventing input rail collapse in shared supplies. |
| Output overvoltage protection (OVP) | Triggers at 120% nominal (3.96 V), discharging output via LS switch to protect downstream 3.3 V logic. |
| Pulse-by-pulse current sensing | Monitors both HS peak and LS valley currents-ensures robust short-circuit protection across full duty cycle range. |
| Voltage sequencing support | EN pin enables controlled power-up timing relative to other rails-critical for FPGA and multi-rail SoC systems. |
Applications
| Industrial 24 V Power Systems | Sensors and Always-On Nodes |
|---|---|
|
Use Scenario: Power conversion in PLC I/O modules and fieldbus gateways operating from unregulated 24 V DC rails. IC Role / Device Role / Timing Role: Primary buck regulator supplying 3.3 V to ARM Cortex-M microcontrollers and isolated RS-485 transceivers. Use Value: 38 V max input withstands load-dump transients; 20 µA IQ extends uptime in battery-backed backup operation. |
Use Scenario: Continuous monitoring nodes in predictive maintenance systems deployed in remote machinery. IC Role / Device Role / Timing Role: Always-on power source for ultra-low-power sensor signal chains and BLE/Wi-Fi MCUs. Use Value: 1–6 µA quiescent current enables >5-year runtime on single 24 V alkaline pack; OVP guards against aging battery overvoltage. |
| Smart Meters | Robot Cleaners |
|
Use Scenario: Metering head in DIN-rail mounted electricity meters with optical/RF communication interfaces. IC Role / Device Role / Timing Role: Secondary regulator deriving 3.3 V from 24 V auxiliary supply for metrology ADC and real-time clock. Use Value: Thermal shutdown at 165 °C prevents failure during sealed enclosure operation; SO8 package supports automated assembly. |
Use Scenario: Mainboard power stage for navigation MCU and motor driver logic in consumer robot vacuum cleaners. IC Role / Device Role / Timing Role: High-reliability 3.3 V rail generator tolerant of battery voltage sag and motor-induced line noise. Use Value: Internal soft-start avoids brown-out during startup surges; PGND/AGND separation maintains ADC accuracy amid motor switching noise. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMR36520RNXR | 3.8–65 V input, 2 A output, 26 µA IQ, no internal compensation - requires external loop compensation. | Higher input voltage range suits 48 V industrial systems; lacks fixed 3.3 V option - needs external feedback. | Select when input exceeds 38 V or higher output current is required; accept added design complexity for compensation. |
| TPS54202HDDCR | 4.5–28 V input, 2 A output, 2 µA shutdown, adjustable VOUT only - no fixed 3.3 V variant. | Lower max input limits use in 24 V-only systems; smaller SO8 package but no OVP or sequencing support. | Prefer for cost-sensitive 24 V designs where external feedback is acceptable and OVP is handled upstream. |
Compared with L6981N33DR, LMR36520RNXR offers wider VIN and higher current but demands external compensation and lacks fixed-VOUT simplicity; TPS54202HDDCR provides lower shutdown current but omits OVP and fixed 3.3 V integration-making L6981N33DR optimal for drop-in 24 V-to-3.3 V industrial conversion.
Availability
L6981N33DR is available at Aetrix Electronics and suitable for industrial 24 V power systems, smart metering platforms, and robot cleaner mainboards requiring stable component supply with long lifecycle assurance.
Supply support for L6981N33DR 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, MCU, and sensor solutions for industrial, automotive, and consumer markets.
L6981 belongs to ST's high-voltage synchronous buck regulator product line, engineered specifically for robust, low-quiescent-power DC-DC conversion in harsh industrial environments with wide input ranges.
FAQ
What is the function of the EN/CLKIN pin on L6981N33DR?
The EN/CLKIN pin serves as a digital enable input with 1.2 V rising threshold and 2 µA shutdown current. For L6981N33DR (an LCM variant), it does not support clock synchronization-only enable/disable functionality. Pulling it below 0.4 V powers down internal circuitry; above 1.2 V initiates 1.3 ms soft-start. It is VIN-compatible and includes wake-up hysteresis for noise immunity.
Does L6981N33DR require external compensation components?
No. L6981N33DR integrates a complete compensation network optimized for stability with standard output capacitors (e.g., 22 µF MLCC). This eliminates external Type-II or Type-III compensation networks, reducing bill-of-materials count and PCB area while maintaining phase margin >45° across temperature and load conditions per datasheet characterization.
How does the output overvoltage protection (OVP) operate on L6981N33DR?
OVP triggers when VOUT exceeds 120% of nominal (3.96 V), activating the low-side MOSFET to sink up to 1.5 A negative current and discharge the output capacitor. Hysteresis is 2%, so recovery occurs at ~3.88 V. This second-level protection operates independently of feedback loop dynamics and is designed to safeguard downstream 3.3 V logic during fault conditions like open-feedback or sudden load removal.
Can L6981N33DR be used with a 12 V input supply?
Yes. With a 3.5–38 V input range, L6981N33DR fully supports 12 V operation. At 12 V input and 3.3 V output, typical efficiency exceeds 88% at 1 A load. The device maintains regulation down to minimum on-time (85 ns) and supports continuous conduction mode across its full load range, making it suitable for automotive auxiliary power and portable 12 V equipment.
L6981N33DR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.5V
- Voltage - Input (Max):
- 38V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 1.5A
- Frequency - Switching:
- 400kHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
L6981N33DR FAQ
1.How can I place an order for L6981N33DR through Aetrix?
Please submit a Request for Quotation (RFQ) for L6981N33DR 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 L6981N33DR reliable?
The price and inventory of L6981N33DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L6981N33DR is usually 5 days.
3.What payment methods are accepted for L6981N33DR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L6981N33DR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L6981N33DR?
L6981N33DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L6981N33DR 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 L6981N33DR?
For technical support, including L6981N33DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L6981N33DR requirements.
6.How does Aetrix verify that L6981N33DR is sourced from the original manufacturer or authorized distributors?
All L6981N33DR 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 L6981N33DR meets industry standards.
7.What is the process for return or replacement of L6981N33DR?
All L6981N33DR units undergo pre-shipment inspection (PSI). If there is an issue with L6981N33DR, 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 L6981N33DR part is unused and in its original packaging.
Return procedure for L6981N33DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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