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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

STMicroelectronics L6984TR

Name: L6984TR
Brand: STMicroelectronics
SKU: L6984TR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L6984TR

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 10-VFDFN Exposed Pad

Datasheet:: L6984TR.pdf

Description:: IC REG BUCK ADJ/3.3V 10VFDFPN

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Product details

Overview

L6984TR from STMicroelectronics is a 36 V, 400 mA synchronous step-down switching regulator with constant-on-time (COT) control, integrated high- and low-side MOSFETs, and dual operating modes (LCM/LNM). It delivers 400 mA DC output current across 4.5–36 V input, supports adjustable output from 0.9 V, achieves 75 µA quiescent current in Low Consumption Mode at 3.3 V output, and features PGOOD open-collector signaling for power sequencing-used in automotive battery-powered systems requiring ultra-low standby power.

For engineers reviewing the L6984TR datasheet, L6984TR pinout, L6984TR application, or L6984TR equivalent, key selection criteria include light-load efficiency (75 µA IQ in LCM), adjustable switching frequency (250–600 kHz), VBIAS-assisted biasing for efficiency optimization, valley current limit (350 mA), and thermal shutdown protection at 150 °C.

Technical Context

The L6984TR implements a constant-on-time (COT) control architecture with frequency feed-forward correction over VIN, enabling fast load transient response and near-constant switching frequency across input voltage variations. Its on-time generator uses an external R_TON resistor to set nominal f_SW, while internal compensation adapts T_ON dynamically to maintain regulation under varying line/load conditions.

Two user-selectable operating modes are implemented via the LNM pin: Low Noise Mode (LNM) enables constant-frequency PWM for minimal output ripple in audio/sensor applications, while Low Consumption Mode (LCM) employs pulse-skipping to reduce quiescent current to 75 µA at light load. The device integrates a switchover regulator that draws bias current from VBIAS (typically connected to V_OUT) to maximize light-load efficiency.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Current	400 mA DC maximum - supports medium-power embedded loads without external boost stages.
Input Voltage Range	4.5 V to 36 V - compatible with 12 V/24 V automotive batteries and industrial wide-input rails.
Quiescent Current (LCM)	75 µA at V_OUT = 3.3 V - enables >1-year battery life in parking-mode automotive sensors.
Switching Frequency	Adjustable 250–600 kHz - allows EMI tuning and inductor size optimization (e.g., 47 µH @ 500 kHz).
Output Voltage Range	0.9 V to 36 V (adjustable); fixed 3.3 V requires no external resistor divider - simplifies BOM and layout for standard rail generation.
Valley Current Limit	350 mA typical - provides robust short-circuit protection without external sensing components.
PGOOD Output	Open-collector, 4 mA sink capability - enables precise power-rail sequencing and system-level fault reporting.
Thermal Shutdown	150 °C with 20 °C hysteresis - ensures safe operation under sustained overload or poor PCB thermal design.

Pinout & Package

The L6984TR is available in VFDFPN10 (4 mm × 4 mm × 1.0 mm) and VDFPN10 (3 mm × 3 mm × 1.0 mm) packages. Both are exposed-pad, RoHS-compliant, thermally enhanced QFN variants optimized for compact power delivery.

Pin/Terminal	Circuit Role	Design Meaning
PGOOD	Power Good status indicator	Open-collector output pulled low when FB voltage drops below 84% of target - used for system power sequencing and fault detection.
FB	Inverting input of error amplifier	Senses regulated output via external divider (or directly tied to VCC for fixed 3.3 V) - reference voltage is 0.9 V typical.
TON	Frequency setting node	Connects to VIN via resistor (RTON) to program switching frequency (250–600 kHz) - board parasitics require scope calibration.
EN	Enable control input	Active-high logic input (2.6 V threshold); tie to VIN if always enabled - supports system-level power gating.
GND	Power ground reference	Main return path for high-current switching loop - must be connected to exposed thermal pad for optimal thermal performance.
LX	Switching node	Drives external inductor; connects internally to high- and low-side MOSFETs - requires low-inductance layout to minimize EMI.
VIN	Main input supply	Accepts 4.5–36 V; powers internal circuitry and high-side switch - requires local 10 µF ceramic input capacitor.
VCC	Internal LDO output	3.3 V regulated supply for control logic; bypassed with 1 µF capacitor - sourced from VBIAS when >3.2 V to improve light-load efficiency.
VBIAS	Bias voltage input	Connected to V_OUT to supply analog circuitry; reduces IQ by bypassing internal LDO - improves efficiency at light load.
LNM	Mode selection strap	Tied to VCC for Low Noise Mode (constant f_SW), GND for Low Consumption Mode (pulse skipping) - determines ripple vs. efficiency trade-off.

Key Features

Feature	Design Value
Synchronous rectification	Integrated high- and low-side MOSFETs eliminate external diode losses - achieves >90% efficiency at medium-to-heavy load.
Constant-on-time (COT) control	No external compensation required - stable with ceramic output capacitors (including zero-ESR types) and fast transient response (<10 µs).
VBIAS-assisted biasing	Draws quiescent current from regulated output instead of VIN - reduces IQ by up to 70% in LCM mode at light load.
Dual operating modes (LCM/LNM)	User-selectable via single pin - LCM maximizes battery life in parking-mode systems; LNM minimizes conducted noise in sensor/audio rails.
No-resistor 3.3 V configuration	FB tied to VCC enables fixed 3.3 V output without external divider - reduces component count, cost, and layout area.
Pulse-by-pulse current limiting	Valley current sensing on low-side switch - provides accurate, cycle-by-cycle overcurrent protection without sense resistors.

Applications

Automotive Parking Sensors

Industrial Smart Meters

Use Scenario: Ultrasonic parking assist modules powered by vehicle battery during extended parking periods.

IC Role / Device Role / Timing Role: Primary 3.3 V power supply with ultra-low IQ (75 µA) in Low Consumption Mode to extend battery life beyond 12 months.

Use Value: Eliminates need for external enable logic or sleep controllers - direct integration reduces system BOM and failure points.

Use Scenario: Battery-backed real-time clock and metrology ICs in electricity meters requiring stable 3.3 V rail during mains outage.

IC Role / Device Role / Timing Role: Standby power regulator delivering 400 mA peak during meter wake-up events while maintaining <100 µA average IQ.

Use Value: Meets IEC 62053-21 Class 0.2 accuracy requirements by minimizing voltage droop during load transients.

Automotive Cabin Sensors

Portable Medical Monitors

Use Scenario: Occupancy and air quality sensors mounted in vehicle cabin, powered from 12 V battery with strict EMI limits.

IC Role / Device Role / Timing Role: Low-noise 3.3 V supply operating in Low Noise Mode (LNM) to avoid interference with analog sensor front-ends.

Use Value: Maintains <10 mV_pp output ripple across 1–400 mA load range - preserves signal integrity of 24-bit ADCs.

Use Scenario: Portable ECG and SpO₂ monitors using coin-cell or Li-ion batteries requiring long runtime and clean analog rails.

IC Role / Device Role / Timing Role: Main system regulator supporting 3.3 V microcontroller, BLE radio, and analog front-end with dynamic load switching.

Use Value: Dual-mode operation allows firmware to switch between LCM (during sleep) and LNM (during measurement) - optimizing both battery life and signal fidelity.

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
TPS62840DRVR	Lower IQ (300 nA shutdown, 75 nA operation), but max 1 A output and 6 V input - not suitable for 36 V automotive input.	Targeted at ultra-low-power IoT sensors, not automotive or industrial wide-input systems.	Select only for sub-6 V battery-powered designs where 36 V tolerance is unnecessary.
MP2451DT-LF-Z	4.5–36 V input, 600 mA output, but uses voltage-mode control and requires external compensation - slower transient response than COT.	Used in cost-sensitive industrial supplies where EMI filtering is less critical than in automotive.	Choose when design prioritizes lower BOM cost over transient performance and light-load efficiency.

Compared with TPS62840DRVR and MP2451DT-LF-Z, the L6984TR uniquely combines 36 V input tolerance, COT-based fast transient response, and dual-mode operation - making it the only option among the three qualified for automotive parking-mode and sensor-rail applications demanding both wide VIN and sub-100 µA IQ.

Availability

L6984TR is available at Aetrix Electronics and suitable for automotive battery-powered systems, industrial smart metering, portable medical devices, and cabin sensor modules requiring stable component supply across extended temperature ranges (−40 °C to +125 °C junction).

Supply support for L6984TR 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 microcontrollers, power management ICs, and analog/mixed-signal devices for automotive, industrial, and consumer markets.

The L6984TR belongs to ST's high-efficiency monolithic DC-DC converter product line, engineered specifically for automotive and industrial applications requiring wide-input voltage operation, ultra-low quiescent current, and robust thermal performance in compact packages.

FAQ

What is the recommended input capacitor for L6984TR in a 12 V automotive application?

A minimum 10 µF X7R ceramic capacitor rated for ≥25 V must be placed within 3 mm of VIN and GND pins. For robustness against load dump transients, ST recommends adding a parallel 47 µF tantalum or polymer capacitor. Total effective capacitance should exceed 22 µF with ESR < 50 mΩ to ensure stable operation during cold-crank (6.5 V min) and load-dump (40 V max) events.

How does the VBIAS pin improve light-load efficiency?

VBIAS allows the internal bias regulator to draw current from the regulated output (e.g., 3.3 V) instead of VIN. When VBIAS > 3.2 V, the internal LDO is disabled and bias current is sourced directly from VBIAS, reducing total input current by up to 70% in Low Consumption Mode. This is confirmed by datasheet IQ measurements: 75 µA with VBIAS = 3.3 V vs. 230 µA with VBIAS = GND.

Can L6984TR operate without an external feedback resistor divider?

Yes - for fixed 3.3 V output, connect FB directly to VCC and tie VBIAS to VOUT. This leverages the internal 0.9 V reference and built-in 3.67× divider ratio (3.3 V / 0.9 V), eliminating external resistors. The configuration is validated in Figure 1 and Section 3.1 of the datasheet, with output accuracy maintained at ±2.1% (3.23–3.37 V).

What is the purpose of the TON pin, and how is its resistor value calculated?

The TON pin sets switching frequency via an external resistor (R_TON) between VIN and TON. Nominal f_SW ≈ 0.9 × R_TON × C_INT / V_IN, where C_INT = 7.5 pF typical. For 500 kHz at 12 V, R_TON ≈ 1.0 MΩ. However, board parasitics (C_PAR) require oscilloscope validation - ST provides R_TON/C_TON design curves in Figures 10–13 for precision tuning.

L6984TR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 10-VFDFN Exposed Pad

Packaging:: Tape & Reel (TR)

Product Status:: Active

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Adjustable (Fixed)

Number of Outputs:: 1

Voltage - Input (Min):: 4.5V

Voltage - Input (Max):: 36V

Voltage - Output (Min/Fixed):: 0.9V (3.3V)

Voltage - Output (Max):: 28V

Current - Output:: 400mA

Frequency - Switching:: 250kHz ~ 600kHz

Synchronous Rectifier:: Yes

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 10-VFDFPN (4x4)

L6984TR FAQ

1.How can I place an order for L6984TR through Aetrix?

Please submit a Request for Quotation (RFQ) for L6984TR 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 L6984TR reliable?

The price and inventory of L6984TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L6984TR is usually 5 days.

3.What payment methods are accepted for L6984TR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L6984TR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L6984TR?

L6984TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L6984TR 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 L6984TR?

For technical support, including L6984TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L6984TR requirements.

6.How does Aetrix verify that L6984TR is sourced from the original manufacturer or authorized distributors?

All L6984TR 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 L6984TR meets industry standards.

7.What is the process for return or replacement of L6984TR?

All L6984TR units undergo pre-shipment inspection (PSI). If there is an issue with L6984TR, 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 L6984TR part is unused and in its original packaging.

Return procedure for L6984TR:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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