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

STMicroelectronics L6997S

Name: L6997S
Brand: STMicroelectronics
SKU: L6997S
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L6997S

Manufacturer:: STMicroelectronics

Category:: DC DC Switching Controllers

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

Datasheet:: L6997S.pdf

Description:: IC REG CTRLR BUCK 20TSSOP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L6997S 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 output with lossless valley current limiting, remote sensing, and latched OVP/UVP protection. It drives external high- and low-side MOSFETs in buck topologies for CPU, DSP, and memory power supplies in networking and mobile applications.

For engineers reviewing the L6997S datasheet, L6997S pinout, L6997S application, or L6997S equivalent, key selection criteria include its 0.6V reference accuracy, selectable sinking mode, 600µA quiescent current, pulse-skipping at light loads, and compatibility with >20A output designs using external FETs and bootstrap gate drive.

Technical Context

The L6997S implements a voltage-feed-forward constant-on-time (COT) control architecture where Ton = K_OSC × V_SENSE/V_OSC + τ, enabling near-constant switching frequency across wide input ranges and ultrafast load transient response. Its hysteretic loop lacks an internal clock and initiates switching only when V_FB < V_REF, minimum off-time has elapsed, and current limit is not active.

Loop stability is enhanced via optional integrator insertion (INT–VFB short + capacitor to VOUT), which adds a DC pole to correct static error from PCB trace drops and output ripple; internal clamping (V_REF−50mV to V_REF+150mV) limits overshoot during transients. The zero-crossing comparator enables natural PFM operation below ~50% of inductor ripple current.

Key Specifications

Parameter	Value and Actual Design Meaning
V_REF	0.6 V ±1% - sets precise output regulation point; supports sub-1V core rails for modern processors.
V_IN Range	1 V to 35 V - accommodates wide-input industrial and telecom bus voltages while maintaining regulation.
I_Q (V_CC)	600 µA typical - enables low-power standby modes without sacrificing startup reliability.
Current Limit	Lossless valley sensing via R_DS(on) - eliminates sense resistor, preserves efficiency, and supports bidirectional (sinking) mode.
Topology	Constant-on-time with feed-forward - delivers <10 µs load transient recovery and input-voltage-invariant frequency tuning.
Protections	Latched OVP/UVP on V_SENSE, PGOOD open-drain status, and anti-cross-conduction drivers - ensures safe shutdown under fault conditions.
Efficiency	94% @ 3.3 V → 2.5 V - achieved via low-driver losses, adaptive dead-time control, and PFM at light loads.

Pinout & Package

The L6997S is housed in a thermally enhanced TSSOP20 package (4.4 mm × 6.5 mm, 0.65 mm pitch) with exposed thermal pad for improved power dissipation in high-current DC/DC modules.

Pin/Terminal	Circuit Role	Design Meaning
1 NOSKIP	Mode select	Connect to V_CC to disable pulse skipping and enforce continuous conduction mode.
2 GNDSENSE	Remote ground reference	Compensates for PCB trace IR drop between regulator output and load ground point.
3 INT	Integrator output	Enables DC error correction when shorted to V_FB and connected via capacitor to V_OUT.
4 V_SENSE	OVP/UVP monitor & feedback	Detects over/undervoltage relative to V_REF; provides integrator input and feed-forward path.
5 V_CC	Main supply rail	3–5.5 V bias for logic and gate drivers; powers internal reference and comparators.
6 GND	Signal ground	Reference for analog circuitry; separate from PGND to minimize noise coupling.
7 V_REF	Precision reference	0.6 V ±1% bandgap source; capable of sourcing/sinking 250 µA for external filtering.
8 V_FB	PWM comparator input	Negative input of error amplifier; tied to V_SENSE or INT to close regulation loop.
9 OSC	Voltage feed-forward input	Accepts resistive divider from V_IN to set stable f_SW; must be 50 mV–1 V for linearity.
10 SS	Soft-start ramp	5 µA current source charges external capacitor; controls current limit ramp and disables protections until 1 V.
11 ILIM	Current limit threshold	Voltage set by external R_ILIM to GND; defines valley current limit with ±2% accuracy.
12 SHDN	Enable/disable control	Logic-low disables all drivers and internal circuitry; requires pull-up or active drive.
13 OVP	Fault indicator	Open-drain output pulled high externally during overvoltage latch condition.
14 PGOOD	Power-good status	Open-drain output pulled high when V_OUT is within 89–110% of target; pulled low on fault.
15 PGND	Power ground return	Low-side driver return path; isolated from signal GND to reduce switching noise injection.
16 LGATE	Low-side driver output	Drives LS MOSFET gate; rise/fall times ≤90 ns into 14 nF load at 3.3 V.
17 V_DR	LS driver supply	3–5.5 V supply for low-side gate driver; decoupling required near pin.
18 PHASE	HS driver return	Floating return for high-side driver; connects to switch node between HS/LS FETs.
19 HGATE	High-side driver output	Drives HS MOSFET gate; rise/fall times ≤100 ns into 7 nF load at 3.3 V.
20 BOOT	Bootstrap supply	Charged via external diode/capacitor; supplies floating HS driver during conduction.

Key Features

Feature	Design Value
Constant-on-time control	Delivers <10 µs load transient recovery without compensation network redesign.
Lossless valley current limit	Eliminates power-wasting sense resistor while supporting bidirectional (sink) current mode.
Remote sensing (GNDSENSE + VSENSE)	Corrects up to 50 mV of static error from PCB trace resistance between output cap and load.
Pulse-skipping at light loads	Reduces I_Q to ~600 µA and improves light-load efficiency by disabling switching cycles.
Latched OVP/UVP with PGOOD	Ensures system-level safety by halting switching and asserting fault signals until manual reset.

Applications

Networking Power Modules

Mobile Baseband Processors

Use Scenario: Regulating 1.2 V/15 A supply for Ethernet PHY and switch ASICs in compact 1U rack units.

IC Role / Device Role / Timing Role: Primary synchronous buck controller managing gate timing, current limiting, and OVP latching.

Use Value: Remote sensing compensates for 30 mΩ board trace resistance; COT topology maintains <±15 mV output deviation during 8 A/µs load steps.

Use Scenario: Generating 0.85 V core voltage for LTE modem SoCs in battery-powered handheld devices.

IC Role / Device Role / Timing Role: Adaptive step-down controller enabling PFM mode below 200 mA to extend battery runtime.

Use Value: 600 µA quiescent current and pulse-skipping reduce no-load power to <1.5 mW; 0.6 V reference ensures accurate low-V_OUT scaling.

CPU Voltage Regulator Modules

DSP Memory Subsystems

Use Scenario: Delivering dynamically scaled 0.7–1.3 V/25 A output for x86 microprocessors in embedded industrial controllers.

IC Role / Device Role / Timing Role: High-current buck controller with integrator loop for tight DC regulation under variable thermal load.

Use Value: INT–VFB integrator reduces static error to <5 mV despite 100 mV peak-to-peak output ripple; latched UVP prevents brownout crashes.

Use Scenario: Supplying 1.5 V DDR3 termination and 1.2 V I/O rails for multi-core DSPs in radar signal processing boards.

IC Role / Device Role / Timing Role: Dual-rail controller coordinating sequencing via SHDN and PGOOD handshaking.

Use Value: Independent OVP/UVP on V_SENSE detects rail collapse before data corruption; PGND isolation minimizes switching noise on sensitive analog paths.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TPS54620	Fixed-frequency current-mode PWM (not COT); integrated FETs (6 A max); no remote GND sensing.	Targeted at mid-power integrated solutions; unsuitable for >20 A or ultra-fast transient applications.	Select when board space is constrained and output current ≤6 A; avoid for high-transient networking modules.
ISL8113	Voltage-mode COT controller; supports 40 V input; no sinking mode or integrator loop; different pinout.	Designed for higher-voltage industrial DC/DC; lacks V_SENSE-based OVP latching and GNDSENSE correction.	Prefer for 36 V input systems requiring fast transients but no bidirectional current capability or precision remote sensing.

Compared with TPS54620 and ISL8113, the L6997S uniquely combines lossless valley current limiting, remote ground sensing, and integrator-based DC error correction-making it optimal for high-accuracy, high-current, low-voltage CPU/DSP supplies where board-level IR drop and ripple-induced static error must be actively suppressed.

Availability

L6997S is available at Aetrix Electronics and suitable for networking power modules, mobile baseband processor supplies, and CPU voltage regulator modules requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for L6997S 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 analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The L6997S belongs to ST's high-efficiency DC/DC controller product line, engineered specifically for low-voltage, high-current point-of-load regulation in space-constrained networking and mobile platforms demanding fast transient response and precision output accuracy.

FAQ

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

The L6997S supports a minimum regulated output voltage of 0.6 V, defined by its internal ±1% precision bandgap reference (V_REF). Stability at this level is achieved through remote sensing (V_SENSE and GNDSENSE), integrator loop correction (INT–V_FB), and constant-on-time control that maintains regulation even with large input variations or PCB trace resistance up to 50 mΩ.

How does the lossless current limit function without a sense resistor?

The L6997S senses inductor current by monitoring the voltage drop across the low-side MOSFET's R_DS(on) using the ILIM pin. An external resistor (R_ILIM) sets the threshold voltage; the internal comparator triggers when V_ILIM exceeds this value, enforcing valley current limiting without dissipative external components-preserving efficiency and thermal margin.

Can the L6997S operate in forced continuous conduction mode (FCCM)?

Yes-connecting the NOSKIP pin to V_CC disables pulse skipping and forces continuous conduction mode. This eliminates low-frequency beat notes in noise-sensitive applications and ensures deterministic switching frequency, though at the cost of reduced light-load efficiency compared to native PFM operation.

What are the critical layout requirements for reliable boot capacitor operation?

A low-ESR ceramic boot capacitor (typically 0.1 µF) must be placed within 3 mm of the BOOT and PHASE pins, with a Schottky diode (e.g., BAT54) connecting V_CC to BOOT. The PHASE trace must be short and wide to minimize inductance; insufficient boot charge causes HGATE dropout and shoot-through risk due to inadequate high-side driver voltage during switching transitions.

L6997S Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Active

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

L6997S FAQ

1.How can I place an order for L6997S through Aetrix?

Please submit a Request for Quotation (RFQ) for L6997S 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 L6997S reliable?

The price and inventory of L6997S are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L6997S is usually 5 days.

3.What payment methods are accepted for L6997S?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L6997S transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L6997S?

L6997S orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L6997S 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 L6997S?

For technical support, including L6997S datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L6997S requirements.

6.How does Aetrix verify that L6997S is sourced from the original manufacturer or authorized distributors?

All L6997S 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 L6997S meets industry standards.

7.What is the process for return or replacement of L6997S?

All L6997S units undergo pre-shipment inspection (PSI). If there is an issue with L6997S, 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 L6997S part is unused and in its original packaging.

Return procedure for L6997S:

1.Submit a request within 90 days.

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

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