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STMicroelectronics L6981CDR
- Part No.:
- L6981CDR
- Manufacturer:
- STMicroelectronics
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
L6981CDR.pdf
- Description:
- IC REG BUCK ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,457
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Product details
Overview
L6981CDR from STMicroelectronics is a synchronous monolithic step-down DC-DC converter delivering up to 1.5 A output current with 20 µA quiescent current (LCM version), operating from 3.5 V to 38 V input, supporting adjustable or fixed 3.3 V/5 V outputs, and featuring internal compensation in SO8 package - used in industrial 24 V bus power supplies and always-on sensor nodes.
For engineers reviewing the L6981CDR datasheet, L6981CDR pinout, L6981CDR application, or L6981CDR equivalent, key selection criteria include light-load efficiency mode (LCM vs LNM), EN/CLKIN dual-function pin behavior, output overvoltage protection trip at 120% nominal, soft-start duration of 1.3 ms, and SO8 thermal resistance of 65 °C/W.
Technical Context
The L6981CDR implements peak current mode control with integrated high-side and low-side MOSFETs (RDS(on) = 0.175 Ω / 0.125 Ω), fixed 400 kHz switching frequency (typ.), and internal slope compensation to prevent subharmonic oscillation. It supports two operational modes: LCM for ultra-low IQ (1–6 µA in fixed-VOUT mode) and LNM for constant-frequency PWM and reduced output ripple.
Its EN/CLKIN pin provides enable/disable control with dual thresholds (VWAKE_UP = 0.7 V, VEN = 1.2 V) and - in LNM variants only - accepts external 200–500 kHz synchronization clock. Output voltage regulation uses an error amplifier with 0.85 V reference (±0.5% over temperature) and built-in overvoltage protection triggering at 115–125% VREF.
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 Current | 1.5 A DC - sufficient for powering microcontrollers, sensors, and communication ICs in decentralized nodes. |
| Quiescent Current (LCM) | 1 µA (typ., fixed-VOUT) - enables multi-year operation in battery-powered always-on applications. |
| Switching Frequency | 400 kHz (typ.) - balances EMI performance and inductor size; synchronizable to external clock in LNM mode. |
| Voltage Reference | 0.85 V ±0.5% - ensures tight output regulation across temperature; supports 3.3 V/5 V fixed or adjustable outputs via FB divider. |
| Overvoltage Protection | 120% VREF trip with 2% hysteresis - discharges output capacitor via low-side MOSFET to limit transient overshoot. |
| Thermal Shutdown | 165 °C with 30 °C hysteresis - protects against sustained overload or poor PCB heatsinking in enclosed enclosures. |
Pinout & Package
Package: SO8 (SOIC-8, 150 mil width), surface-mount, with exposed thermal pad (PGND-connected). Thermal resistance RthJA = 65 °C/W on ST's 2-layer 2-oz Cu demo board.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 SW | Switching node | Connects to inductor and bootstrap capacitor; carries high di/dt pulses; requires tight layout to minimize ringing. |
| 2 BOOT | Bootstrap supply | Drives high-side gate via 100 nF capacitor between BOOT and SW; critical for NMOS gate drive during HS conduction. |
| 3 VCC | Analog supply rail | Powers internal bandgap, error amp, and logic; requires ≥1 µF ceramic bypass to AGND for stability. |
| 4 VOUT/FB | Output sense / feedback | In fixed-VOUT versions (e.g., L6981CDR), functions as regulated output; in adjustable versions, connects to external resistor divider. |
| 5 EN/CLKIN | Enable & sync input | Digital enable with 1.2 V threshold; in LNM variants only, accepts 200–500 kHz external clock for EMI reduction. |
| 6 AGND | Analog ground | Reference for error amplifier and internal circuits; must be separated from PGND and joined at single point near VCC capacitor. |
| 7 VIN | Main input supply | Accepts 3.5–38 V; requires local 10 µF ceramic input capacitor to suppress high-frequency noise and supply transients. |
| 8 PGND | Power ground | Return path for high-current switches and inductor; connects to thermal pad; must be low-inductance plane under SW/VIN pins. |
Key Features
| Feature | Design Value |
|---|---|
| Internal compensation network | Eliminates need for external Type-II/III compensation components, reducing BOM count and layout sensitivity. |
| Two light-load modes (LCM/LNM) | LCM enables <1 µA IQ in fixed-output mode; LNM maintains constant 400 kHz switching for predictable EMI filtering. |
| Integrated soft-start (1.3 ms) | Prevents inrush current into output capacitors and avoids input voltage droop during power-up sequencing. |
| Output overvoltage protection (OVP) | Active discharge via low-side MOSFET limits VOUT overshoot to ≤125% nominal, protecting downstream loads. |
| VIN-compatible EN pin | Operates directly from 24 V bus without level-shifting; dual-threshold wake-up (0.7 V) and enable (1.2 V) reduce false triggers. |
Applications
| Industrial 24 V Power Supply | Smart Meter Power Management |
|---|---|
|
Use Scenario: Regulating unregulated 24 V factory bus to 3.3 V for PLC I/O modules and fieldbus transceivers. IC Role / Device Role / Timing Role: Primary buck regulator providing isolated, stable 3.3 V rail with high PSRR and load-step immunity. Use Value: 38 V max input withstands 48 V transients per IEC 61000-4-5; 1.5 A output supports multiple digital loads simultaneously. |
Use Scenario: Powering metrology ASIC, RTC, and RF module in battery-backed smart electricity meters. IC Role / Device Role / Timing Role: Always-on DC-DC converter maintaining 3.3 V during mains failure using supercapacitor or LiSOCl₂ backup. Use Value: 1 µA quiescent current (LCM mode) extends battery life beyond 10 years; OVP safeguards meter accuracy-critical analog front-end. |
| Robot Cleaner Control Board | Decentralized Sensor Node |
|
Use Scenario: Generating 5 V for motor drivers and MCU on compact robotic vacuum cleaner mainboard. IC Role / Device Role / Timing Role: High-efficiency buck stage stepping down 24 V battery pack to 5 V, synchronized to system clock to avoid beat frequencies. Use Value: LNM mode enables EMI-controlled 400 kHz switching; thermal shutdown prevents overheating during brushless motor stall conditions. |
Use Scenario: Local power conversion for wireless vibration/temperature sensors mounted on rotating machinery. IC Role / Device Role / Timing Role: Low-noise, high-reliability regulator supplying 3.3 V to ultra-low-power MCU and BLE SoC in harsh EMI environments. Use Value: SO8 package with thermal pad ensures stable operation at 85 °C ambient; 20 µA IQ enables energy harvesting compatibility. |
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 | Higher 65 V input rating; 2 A output; 26 µA IQ; no LCM/LNM mode selection; requires external compensation. | Better suited for automotive 48 V systems; lacks light-load optimization for battery longevity. | Select if input exceeds 38 V or >1.5 A output needed; accept added design complexity for external loop compensation. |
| TPS54202HDDCR | 17 V max input; 2 A output; 25 µA IQ; integrated FETs; no OVP; requires external soft-start capacitor. | Targeted at lower-voltage consumer electronics; missing OVP and thermal hysteresis critical for industrial reliability. | Choose only for cost-sensitive 12 V applications where 38 V tolerance and robust protection are not required. |
Compared with LMR36520RNXR and TPS54202HDDCR, the L6981CDR uniquely combines 38 V input tolerance, sub-µA light-load IQ in fixed-VOUT mode, integrated OVP, and dual-mode operation - making it optimal for long-life, high-reliability 24 V industrial power rails.
Availability
L6981CDR is available at Aetrix Electronics and suitable for industrial 24 V power systems, smart meter deployments, and robot cleaner production requiring stable component supply and long-term lifecycle assurance.
Supply support for L6981CDR 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, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.
The L6981 belongs to ST's high-voltage monolithic DC-DC converter product line, engineered specifically for robust, low-maintenance power conversion in industrial automation, smart infrastructure, and battery-backed IoT edge devices.
FAQ
What is the difference between L6981CDR and L6981IDR?
The L6981CDR is the fixed 3.3 V output version in SO8 package, while L6981IDR is the adjustable version (0.85 V to VIN) with FB pin functionality. Both share identical input range, 1.5 A current capability, LCM/LNM modes, and SO8 packaging - but differ in internal feedback divider and output voltage setting.
Does L6981CDR support external clock synchronization?
No - only LNM versions (e.g., L6981ADJ-LNM, L698133-LNM) support synchronization via the EN/CLKIN pin. The L6981CDR is an LCM variant; its EN pin operates solely as an enable input with 1.2 V threshold and no clock input capability.
How does the switch-over feature reduce input current in L6981CDR?
In fixed-VOUT versions like L6981CDR, the switch-over feature powers internal circuitry from VOUT instead of VIN at light loads, reducing total input current to IQVIN ≈ IQOPVIN + (VOUT/VIN) × IQVOUT/η - achieving as low as 1 µA typical from VIN when VOUT = 3.3 V and VIN = 24 V.
Can L6981CDR safely drive a 100 µF output capacitor?
Yes - the internal soft-start (1.3 ms) and current-limited startup prevent inrush damage. However, ensure COUT ESR ≤ 10 mΩ and use ceramic or polymer types; large electrolytics may destabilize the internal compensation due to phase shift beyond the designed margin.
L6981CDR 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:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.5V
- Voltage - Input (Max):
- 38V
- Voltage - Output (Min/Fixed):
- 0.85V
- Voltage - Output (Max):
- 38V
- 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
L6981CDR FAQ
1.How can I place an order for L6981CDR through Aetrix?
Please submit a Request for Quotation (RFQ) for L6981CDR 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 L6981CDR reliable?
The price and inventory of L6981CDR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L6981CDR is usually 5 days.
3.What payment methods are accepted for L6981CDR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L6981CDR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L6981CDR?
L6981CDR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L6981CDR 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 L6981CDR?
For technical support, including L6981CDR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L6981CDR requirements.
6.How does Aetrix verify that L6981CDR is sourced from the original manufacturer or authorized distributors?
All L6981CDR 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 L6981CDR meets industry standards.
7.What is the process for return or replacement of L6981CDR?
All L6981CDR units undergo pre-shipment inspection (PSI). If there is an issue with L6981CDR, 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 L6981CDR part is unused and in its original packaging.
Return procedure for L6981CDR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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