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STMicroelectronics L6981C50DR
- Part No.:
- L6981C50DR
- Manufacturer:
- STMicroelectronics
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
L6981C50DR.pdf
- Description:
- IC REG BUCK 5V 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,933
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Product details
Overview
L6981C50DR from STMicroelectronics is a synchronous step-down DC-DC converter delivering up to 1.5 A output current with 3.5–38 V input range, fixed 5.0 V output, and 550 µA typical quiescent current in low-noise mode (LNM). It features internal compensation, 400 kHz nominal switching frequency, output overvoltage protection, and EN/CLKIN pin for enable or external synchronization-designed for smart meters and robot cleaners requiring stable, low-noise 5 V rail from 24 V bus or battery.
For engineers reviewing the L6981C50DR datasheet, L6981C50DR pinout, L6981C50DR application, or L6981C50DR equivalent, key selection criteria include its LNM-mode constant-frequency operation, VIN-compatible enable threshold (1.2 V), 0.85 V internal reference accuracy (±0.5%), thermal shutdown at 165 °C, and SO8 package compatibility with standard PCB layout practices for industrial power conversion.
Technical Context
The L6981C50DR implements peak current mode control with forced PWM in LNM configuration, ensuring constant 360–440 kHz switching across load conditions to minimize conducted EMI. Its integrated high-side (0.175 Ω) and low-side (0.125 Ω) MOSFETs support efficient 5 V regulation from 24 V input with <1.3 ms internal soft-start and pulse-by-pulse current sensing on both switches.
It uses an embedded transconductance error amplifier with internal compensation, eliminating external loop components. The EN/CLKIN pin serves dual function: digital enable with 1.2 V rising threshold and 200–500 kHz synchronization input for noise-sensitive systems-only active in LNM variants like this C50DR part.
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 5.0 V ±0.45% (–40 to 125 °C) - precision internal feedback divider enables accurate 5 V rail for MCU peripherals and sensors. |
| Max Output Current | 1.5 A DC - sufficient for powering microcontrollers, communication ICs, and motor drivers in decentralized nodes. |
| Quiescent Current (LNM) | 550 µA typ. from VIN - enables always-on operation in smart meters with minimal standby power drain. |
| Switching Frequency | 400 kHz typ. (360–440 kHz) - balances efficiency, EMI filtering size, and transient response for compact designs. |
| Thermal Shutdown | 165 °C with 30 °C hysteresis - protects against sustained overload or poor heatsinking in enclosed industrial enclosures. |
| Overvoltage Protection | 120% VOUT trip (6.0 V) with 2% hysteresis - actively discharges output capacitor via low-side FET to prevent downstream damage. |
Pinout & Package
Package: SO8 (Small Outline, 8-pin, 1.27 mm pitch), RoHS-compliant, thermally enhanced for 1.5 A operation with RthJA = 65 °C/W on 2-layer demo board.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 SW | Switching node | Connection point between internal high-side and low-side MOSFETs; requires low-inductance routing to minimize voltage spikes and EMI. |
| 2 BOOT | Bootstrap capacitor terminal | Connects 100 nF ceramic capacitor to SW to gate-drive high-side FET; critical for proper high-side conduction timing. |
| 3 VCC | Analog supply rail | Powers internal reference and error amplifier; requires ≥1 µF ceramic bypass capacitor to stabilize 3.3 V LDO output. |
| 4 VOUT/FB | Output voltage sense / feedback | In fixed-5V version, functions as VOUT pin; internally connected to precision 0.85 V reference for regulation. |
| 5 EN/CLKIN | Enable input / sync clock input | Digital enable (1.2 V threshold); in LNM mode, accepts 200–500 kHz external clock to synchronize switching and reduce beat frequencies. |
| 6 AGND | Analog ground | Reference for error amplifier and internal circuitry; must be separated from PGND and joined at single point near VCC capacitor. |
| 7 VIN | Main power input | Accepts 3.5–38 V DC; requires 10 µF low-ESR input capacitor close to pin to suppress ripple and transient surges. |
| 8 PGND | Power ground | Return path for high-current switch node and low-side FET; routed with wide copper pour to minimize IR drop and thermal rise. |
Key Features
| Feature | Design Value |
|---|---|
| Low-Noise Mode (LNM) | Forced PWM with constant 400 kHz switching - eliminates variable-frequency burst mode noise, meeting EMC requirements for smart meter RF modules. |
| Internal Soft-Start | 1.3 ms monotonic ramp - limits inrush current during power-up, preventing input voltage sag and system reset in battery-powered robot cleaners. |
| VIN-Compatible Enable | 1.2 V enable threshold referenced to GND - allows direct interfacing with 3.3 V or 5 V logic without level-shifting in industrial PLC I/O modules. |
| Output Overvoltage Protection | Active discharge via low-side FET at 6.0 V - protects connected microcontrollers and ADCs from latch-up or permanent damage during transient faults. |
| Thermal Protection with Hysteresis | 165 °C shutdown + 30 °C recovery - prevents thermal runaway while allowing automatic recovery after cooling, enhancing reliability in sealed enclosures. |
Applications
| Smart Meters | Robot Cleaners |
|---|---|
|
Use Scenario: Metering ICs and RF transceivers require ultra-stable, low-noise 5 V supply in utility-grade electricity meters operating continuously for >10 years. IC Role / Device Role / Timing Role: Primary 5 V power regulator supplying metrology SoC, PLC modem, and secure element with tight load regulation (<0.5%) and minimal ripple. Use Value: LNM mode ensures constant switching frequency avoids interference with narrowband PLC carrier signals (e.g., PRIME or G3-PLC), preserving communication integrity. |
Use Scenario: Autonomous vacuum robots use 24 V battery packs to power motor drivers, vision processors, and sensor fusion units needing clean, efficient 5 V rails. IC Role / Device Role / Timing Role: Main system regulator converting 24 V battery to 5 V for MCU, IMU, and lidar interface ICs with fast transient response to motor startup surges. Use Value: 1.5 A capability and 550 µA LNM quiescent current extend runtime during standby while maintaining low EMI for sensitive optical sensors. |
| Industrial Sensors | Decentralized I/O Nodes |
|
Use Scenario: High-precision analog sensors (e.g., strain gauges, RTDs) in factory automation require isolated, low-noise 5 V supply unaffected by nearby motor drives or switching loads. IC Role / Device Role / Timing Role: Local power regulator on sensor node PCB, rejecting conducted noise from shared 24 V bus using LNM's predictable spectral content. Use Value: Fixed 5.0 V output with ±0.45% tolerance over temperature ensures ADC reference stability, reducing calibration drift in Class A measurement systems. |
Use Scenario: Modular I/O terminals in distributed control systems draw power from centralized 24 V backbone and must operate reliably under varying ambient temperatures (–40 to 85 °C). IC Role / Device Role / Timing Role: Point-of-load regulator delivering 5 V to FPGA configuration memory, CAN transceivers, and optocoupler drivers with robust thermal management. Use Value: SO8 package with 65 °C/W thermal resistance and 165 °C thermal shutdown enable continuous operation in unventilated DIN-rail enclosures without derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS54202DRCT | 3.5–28 V input, 2 A output, 500 kHz, 26 µA IQ (non-LNM), no sync input | Lacks external clock synchronization and fixed 5 V option; higher IQ in light-load but no LNM noise control | Select when higher output current (2 A) is needed and EMI filtering can absorb variable-frequency operation. |
| MP2451DT-LF-Z | 4.5–36 V input, 0.6 A output, 340 kHz, 100 µA IQ, no sync, no OVP | Lower current rating, no overvoltage protection, no synchronization capability, no LNM/LCM modes | Choose only for cost-sensitive, non-critical 5 V rails where full protection and noise control are not required. |
Compared with TPS54202DRCT and MP2451DT-LF-Z, the L6981C50DR uniquely combines 1.5 A capability, LNM-mode EMI control, 5 V fixed output with ±0.45% accuracy, and active OVP-making it optimal for certified smart meter and industrial sensor applications demanding functional safety and regulatory compliance.
Availability
L6981C50DR is available at Aetrix Electronics and suitable for smart meters, robot cleaners, industrial sensors, and decentralized I/O nodes requiring stable component supply with long-term industrial lifecycle support.
Supply support for L6981C50DR 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, specializing in power management, microcontrollers, and automotive ICs with strong industrial and energy infrastructure focus.
The L6981 series targets industrial power conversion with emphasis on wide-input, low-quiescent-current, and noise-controlled operation-specifically engineered for battery-backed and always-on equipment in harsh environments.
FAQ
What is the purpose of the EN/CLKIN pin on the L6981C50DR?
The EN/CLKIN pin serves two distinct functions: as a digital enable input with 1.2 V rising threshold to turn the regulator on/off, and-specifically in LNM versions like the C50DR-as a synchronization input accepting 200–500 kHz external clock signals to align switching edges and reduce beat frequencies in multi-rail systems. This dual role eliminates need for separate enable and sync pins, saving board space.
How does the L6981C50DR achieve low-noise operation?
The L6981C50DR achieves low-noise operation through its Low-Noise Mode (LNM), which enforces constant-frequency PWM control across all load conditions-including light loads-eliminating the variable-frequency burst mode used in LCM variants. This results in predictable, narrowband switching harmonics that are easier to filter and less likely to interfere with sensitive analog or RF circuits in smart meters and sensor nodes.
Does the L6981C50DR require external compensation components?
No, the L6981C50DR features an internally compensated transconductance error amplifier, removing the need for external compensation networks such as RC or R-C networks typically required in adjustable buck controllers. This simplifies design, reduces BOM count, and improves consistency across production units-especially valuable for high-volume industrial applications where layout variability must be minimized.
What protection features are built into the L6981C50DR?
The L6981C50DR integrates six protection features: (1) output overvoltage protection (trip at 120% VOUT), (2) thermal shutdown (165 °C), (3) pulse-by-pulse overcurrent protection on both high-side and low-side switches, (4) undervoltage lockout on VCC, (5) reverse current limiting (1.5 A sink), and (6) internal soft-start to limit inrush current. All operate autonomously without external components.
L6981C50DR 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):
- 5V
- 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
L6981C50DR FAQ
1.How can I place an order for L6981C50DR through Aetrix?
Please submit a Request for Quotation (RFQ) for L6981C50DR 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 L6981C50DR reliable?
The price and inventory of L6981C50DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L6981C50DR is usually 5 days.
3.What payment methods are accepted for L6981C50DR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L6981C50DR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L6981C50DR?
L6981C50DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L6981C50DR 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 L6981C50DR?
For technical support, including L6981C50DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L6981C50DR requirements.
6.How does Aetrix verify that L6981C50DR is sourced from the original manufacturer or authorized distributors?
All L6981C50DR 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 L6981C50DR meets industry standards.
7.What is the process for return or replacement of L6981C50DR?
All L6981C50DR units undergo pre-shipment inspection (PSI). If there is an issue with L6981C50DR, 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 L6981C50DR part is unused and in its original packaging.
Return procedure for L6981C50DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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