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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > DC DC Switching Controllers

STMicroelectronics L6997STR

Name: L6997STR
Brand: STMicroelectronics
SKU: L6997STR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L6997STR

Manufacturer:: STMicroelectronics

Category:: DC DC Switching Controllers

Package:: 20-TSSOP (0.173", 4.40mm Width)

Datasheet:: L6997STR.pdf

Description:: IC REG CTRLR BUCK 20TSSOP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L6997STR from STMicroelectronics is a constant-on-time synchronous step-down controller IC for low-voltage DC/DC conversion, supporting 1V–35V input and regulating down to 0.6V ±1% reference with remote sensing, lossless valley current limit, and integrated high- and low-side gate drivers. It delivers >20A output current in networking power modules and CPU/DSP core supplies.

For engineers reviewing the L6997STR datasheet, L6997STR pinout, L6997STR application, or L6997STR equivalent, this controller enables fast transient response in distributed power systems, supports pulse-skipping at light loads for efficiency, integrates OVP/UVP latched protection, and provides programmable soft-start and integrator-based static error correction.

Technical Context

The L6997STR implements a voltage-feed-forward constant-on-time (COT) topology where Ton = K_OSC × V_SENSE/V_OSC + τ, enabling near-constant switching frequency across wide input ranges. Its hysteretic control loop lacks an internal clock and initiates switching only when V_FB < V_REF, minimum off-time expires, and current limit is not triggered.

It embeds dual gate drivers with adaptive anti-cross-conduction logic-turning on LGATE only after PHASE falls below 250mV and delaying HGATE until LGATE rises above 500mV. The integrator (INT pin) introduces a DC pole via external capacitor to correct static regulation error from PCB trace drop and output ripple.

Key Specifications

Parameter	Value and Actual Design Meaning
V_IN Range	1V to 35V - supports wide-input industrial and telecom bus rails including 3.3V and 5V backplanes.
V_OUT Min / V_REF	0.6V ±1% - enables direct core supply for modern CPUs, DSPs, and low-V_GS MOSFETs.
Topology	Constant On-Time (COT) with voltage feed-forward - ensures fast load transient recovery <10µs and stable operation without external compensation.
Current Limit	Lossless valley current sensing via R_DS(on) - sets precise overcurrent threshold using external R_ILIM, active in both sourcing and sinking modes.
Protections	Latched OVP/UVP on V_SENSE, PGOOD open-drain status, shutdown via SHDN pin - prevents system damage during fault and enables safe restart.
Quiescent Current	600µA typical at V_CC/V_DR = 3.3V - minimizes standby power in battery-backed or always-on mobile applications.
Efficiency	94% at 3.3V→2.5V - achieved via low-driver losses, pulse-skipping at light loads, and optimized gate drive timing.

Pinout & Package

TSSOP20 package with exposed thermal pad (pin 19 = HGATE, pin 20 = BOOT, pin 15 = PGND); RoHS-compliant, moisture sensitivity level MSL3.

Pin/Terminal	Circuit Role	Design Meaning
1 NOSKIP	Mode select input	Connect to V_CC to disable pulse-skipping and force continuous conduction mode with sink capability.
2 GNDSENSE	Remote ground sense	Provides Kelvin connection point to load ground, compensating for PCB trace IR drop in precision regulation.
3 INT	Integrator output	Drives external capacitor to add DC pole in control loop; clamped between V_REF−50mV and V_REF+150mV to limit overshoot.
4 VSENSE	OVP/UVP monitor & feedback	Inputs remote output voltage for protection thresholds and integrator reference; enables valley regulation accuracy.
5 V_CC	Logic supply	Powers internal circuitry; valid range 3V–5.5V; turn-on threshold 2.97V with 90mV hysteresis.
6 GND	Signal ground	Reference for analog comparators and logic; separate from PGND to avoid noise coupling into feedback path.
7 V_REF	0.6V precision reference	Stable ±1% bandgap source; capable of sourcing/sinking 250µA; requires ≤10nF ceramic bypass to GND.
8 V_FB	PWM comparator input	Compares against V_REF; shorted to INT for integrator use or to VSENSE for standard feedback configuration.
9 OSC	Voltage feed-forward input	Accepts resistor divider from V_IN to set switching frequency; must be 50mV–1V for linear COT operation.
10 SS	Soft-start ramp	5µA current source charges external capacitor; active range 0.6V–1V; disables protections until 1V reached.
11 ILIM	Current limit threshold	Voltage input scaled by external R_ILIM to set valley current limit; linear range 10mV–1V.
12 SHDN	Enable/disable control	Active-high logic input; <0.6V = shutdown, >1.2V = active; pulls drivers and logic offline with µA leakage.
13 OVP	Open-drain fault flag	Pulled high externally during overvoltage; latched until SHDN cycle or power cycle clears fault state.
14 PGOOD	Power-good indicator	Open-drain output pulled high when V_OUT within 89–110% of target; pulled low on UVP/OVP latch.
15 PGND	Power ground return	Low-side driver return path; isolated from signal GND to prevent switching noise injection into analog section.
16 LGATE	Low-side MOSFET driver	Drives N-channel sync FET gate; rise/fall time 50–90ns into 14nF load; includes anti-cross-conduction delay.
17 V_DR	Low-side driver supply	3–5.5V supply for LGATE driver; independent of V_CC to support higher gate drive voltages.
18 PHASE	High-side return node	Swinging node tied to inductor; used as return for HGATE driver and zero-cross detection for PFM mode.
19 HGATE	High-side MOSFET driver	Bootstrap-driven output for N-channel high-side FET; rise/fall time 50–100ns into 7nF load.
20 BOOT	Bootstrap capacitor terminal	Connects external capacitor between BOOT and PHASE to generate floating supply for HGATE driver.

Key Features

Feature	Design Value
Constant On-Time Control	Enables sub-10µs load transient response without external loop compensation components.
Remote Sensing (VSENSE + GNDSENSE)	Corrects up to 50mV of static output error caused by PCB trace resistance between regulator and load.
Programmable Valley Current Limit	Uses MOSFET R_DS(on) for lossless sensing; threshold set by single resistor (R_ILIM) with ±10% accuracy.
Latched OVP/UVP Protection	Prevents damage during rail faults; requires explicit SHDN toggle or power cycle to reset, ensuring safe recovery.
Pulse-Skipping at Light Loads	Reduces quiescent current to ~600µA and improves light-load efficiency by disabling switching cycles.

Applications

Networking Power Modules

Mobile Baseband Processors

Use Scenario: Regulating 1.2V/15A core supply from 3.3V mid-rail in 1U network switches with tight thermal constraints.

IC Role / Device Role / Timing Role: Primary step-down controller managing synchronous buck stage with remote sensing and fast transient recovery.

Use Value: Maintains ±1% output accuracy under 5A/µs load steps while delivering 94% peak efficiency and eliminating external compensation.

Use Scenario: Generating 0.9V core voltage for LTE baseband SoCs in handheld devices with battery input ranging 3.2–4.4V.

IC Role / Device Role / Timing Role: Adaptive COT controller enabling pulse-skipping during idle periods and full PWM during burst processing.

Use Value: Extends battery runtime via 600µA quiescent current and avoids audible noise by operating outside 20kHz during light loads.

Distributed CPU Power

DC/DC Module Reference Design

Use Scenario: Providing 0.85V/20A VR12-compatible supply to multi-core x86 processors in embedded servers.

IC Role / Device Role / Timing Role: High-current controller interfacing with digital PMBus supervisors for margining and telemetry.

Use Value: Supports remote sensing and integrator-based DC error correction to meet ±10mV static regulation spec across 15cm PCB traces.

Use Scenario: Core controller in 50W quarter-brick DC/DC module targeting telecom and industrial DIN-rail power systems.

IC Role / Device Role / Timing Role: Fixed-frequency COT controller with latched protections and programmable soft-start for system-level safety compliance.

Use Value: Enables EN 62368-1 certification via OVP/UVP latching, PGOOD sequencing, and thermal-safe gate drive architecture.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MP2940A from Monolithic Power Systems	Fixed-frequency current-mode PWM (not COT); requires external compensation; 0.6V reference; no remote ground sense pin.	Lacks GNDSENSE and integrator (INT), limiting static regulation accuracy in long-trace layouts.	Choose when fixed-frequency EMI control is prioritized over transient speed and trace-drop compensation.
TPS546D24 from Texas Instruments	Dual-loop D-CAP3 control; supports PMBus; 0.5V reference; integrated MOSFET drivers; no dedicated NOSKIP pin.	Includes digital interface and telemetry but requires more external components and lacks sink-mode selection.	Prefer for systems needing real-time telemetry and dynamic voltage scaling over discrete controller simplicity.

Compared with MP2940A and TPS546D24, the L6997STR offers superior transient response via COT architecture, built-in remote sensing for trace-drop correction, and selectable sink-mode operation-making it optimal for space-constrained, high-accuracy analog-regulated power stages without digital overhead.

Availability

L6997STR is available at Aetrix Electronics and suitable for networking power modules, mobile baseband processors, and distributed CPU power systems requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant TSSOP packaging.

Supply support for L6997STR 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 L6997STR belongs to ST's high-efficiency DC/DC controller product line, engineered specifically for low-voltage, high-current point-of-load regulation in telecom infrastructure and portable computing platforms.

FAQ

What is the minimum recommended output voltage and how is it stabilized?

The L6997STR supports a minimum regulated output voltage of 0.6V, defined by its internal ±1% precision bandgap reference (V_REF). Stability is maintained through constant-on-time control with voltage feed-forward, remote sensing (VSENSE + GNDSENSE), and optional integrator compensation (INT pin). This achieves ±10mV static regulation accuracy even with 50mV PCB trace drop.

How does the lossless current limit function and what external component sets it?

The lossless current limit senses the low-side MOSFET's R_DS(on) voltage drop and compares it to a threshold set by an external resistor (R_ILIM) connected between ILIM pin and GND. The ILIM pin voltage is internally scaled by K_ILIM = 1.8 µA/V, so R_ILIM = V_ILIM / (I_VALLEY × K_ILIM). This eliminates sense-resistor power loss and supports both sourcing and sinking modes.

Can the L6997STR operate without an external integrator, and what is the trade-off?

Yes-the L6997STR operates without the integrator by shorting INT to VREF. However, this removes DC error correction for PCB trace IR drop and output ripple-induced valley regulation error. Without the integrator, static regulation degrades by up to 30mV under full load due to trace resistance alone, making it unsuitable for high-accuracy core supplies.

What protection features are latched, and how is the device recovered from fault?

OVP and UVP protections are latched: upon violation, both high- and low-side drivers disable, PGOOD goes low, and OVP goes high. Recovery requires either toggling the SHDN pin (pulling it low then high) or cycling V_CC/V_DR power. No automatic retry occurs-ensuring system safety before re-enabling regulation.

L6997STR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 20-TSSOP (0.173", 4.40mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Output Type:: Transistor Driver

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Number of Outputs:: 1

Output Phases:: 1

Voltage - Supply (Vcc/Vdd):: 3V ~ 5.5V

Frequency - Switching:: -

Duty Cycle (Max):: -

Synchronous Rectifier:: Yes

Clock Sync:: No

Serial Interfaces:: -

Control Features:: Current Limit, Enable, Phase Control, Power Good, Soft Start

Operating Temperature:: -40°C ~ 125°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 20-TSSOP

L6997STR FAQ

1.How can I place an order for L6997STR through Aetrix?

Please submit a Request for Quotation (RFQ) for L6997STR 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 L6997STR reliable?

The price and inventory of L6997STR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L6997STR is usually 5 days.

3.What payment methods are accepted for L6997STR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L6997STR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L6997STR?

L6997STR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L6997STR 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 L6997STR?

For technical support, including L6997STR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L6997STR requirements.

6.How does Aetrix verify that L6997STR is sourced from the original manufacturer or authorized distributors?

All L6997STR 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 L6997STR meets industry standards.

7.What is the process for return or replacement of L6997STR?

All L6997STR units undergo pre-shipment inspection (PSI). If there is an issue with L6997STR, 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 L6997STR part is unused and in its original packaging.

Return procedure for L6997STR:

1.Submit a request within 90 days.

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

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