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

STMicroelectronics ST1S12G18R

Name: ST1S12G18R
Brand: STMicroelectronics
SKU: ST1S12G18R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ST1S12G18R

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: SOT-23-5 Thin, TSOT-23-5

Datasheet:: ST1S12G18R.pdf

Description:: IC REG BUCK 1.8V 700MA TSOT23-5

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Inventory:13,718

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Product details

Overview

ST1S12G18R from STMicroelectronics is a synchronous step-down DC-DC converter IC optimized for powering low-voltage digital cores (e.g., HDD controller logic, FPGA I/O banks, ASIC cores) with fixed 1.8 V output, 0.7 A load capability, 1.7 MHz switching frequency, ±3% output voltage tolerance, and TSOT23-5L package.

For engineers reviewing the ST1S12G18R datasheet, ST1S12G18R pinout, ST1S12G18R application, or ST1S12G18R equivalent, this page delivers verified electrical specs, thermal behavior, enable-controlled power sequencing, feedback-based regulation accuracy, and real-world efficiency curves across load/temperature - all critical for compact, thermally constrained embedded power rails.

Technical Context

This current-mode PWM regulator integrates NMOS and PMOS power switches (R_DS(ON) typ. 0.25 Ω each), internal soft-start, thermal shutdown (130–150 °C), and overcurrent protection (1.6 A limit). Its fixed 1.8 V output is set internally - eliminating external resistor divider components required in adjustable variants.

Operating from 2.5 V to 5.5 V input, it maintains >90% typical efficiency at 100–700 mA loads and achieves <650 µA quiescent current in non-switching mode. The 1.7 MHz fixed-frequency operation enables use of miniature 2.2 µH inductors and 10 µF ceramic capacitors, minimizing PCB footprint in space-constrained applications.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 1.8 V ±3% - ensures stable core supply for 1.8 V logic domains without external feedback resistors.
Max Output Current	0.7 A - sufficient for powering multi-core SoCs, DDR I/O buffers, or sensor interface ASICs.
Switching Frequency	1.7 MHz (typ.) - enables use of sub-3 mm × 3 mm inductors and reduces output ripple without large bulk capacitance.
Quiescent Current	650 µA max (over temp.) - minimizes standby power loss in battery-backed or always-on subsystems.
Input Voltage Range	2.5 V to 5.5 V - compatible with single-cell Li-ion, USB 5 V, or regulated 3.3 V system rails.
Efficiency	90% typ. at 100–700 mA, V_IN = 3.6 V - reduces thermal load in sealed enclosures and extends battery runtime.
Thermal Shutdown	130–150 °C with 15 °C hysteresis - provides robust fault recovery without external thermal monitoring circuitry.

Pinout & Package

TSOT23-5L package: 5-pin ultra-thin surface-mount with 0.95 mm pitch, 2.9 mm × 2.8 mm footprint, and exposed thermal pad (not electrically connected).

Pin/Terminal	Circuit Role	Design Meaning
1 - EN	Enable control input	Active-high logic input; device starts switching when voltage ≥1.5 V, shuts down fully below 0.5 V (I_EN ≤1 µA).
2 - GND	Power and signal ground reference	Primary return path for input/output currents and feedback loop; must be low-impedance connection to minimize noise coupling.
3 - SW	Switch node	Drives external inductor; carries high di/dt square wave (0 to V_IN) at 1.7 MHz; requires tight layout to reduce EMI.
4 - VIN	Main power input	Accepts 2.5–5.5 V; requires local 4.7 µF ceramic decoupling close to pin to suppress high-frequency input ripple.
5 - FB/VO	Feedback / output voltage sense	Internally tied to 1.8 V reference; no external divider needed - simplifies BOM and improves regulation accuracy vs. adjustable versions.

Key Features

Feature	Design Value
Synchronous rectification	Integrated NMOS/PMOS power stage eliminates external Schottky diode - improves efficiency by ~8% vs. asynchronous designs at full load.
Internal soft-start	Gradual output ramp-up prevents inrush current spikes into downstream capacitance - avoids input rail droop and system reset events.
Current-mode PWM control	Provides inherent cycle-by-cycle current limiting and fast transient response (<±5% output deviation for 100→700 mA step, 200 ns edge).
Low-R_DS(ON) switches	0.25 Ω typ. NMOS and PMOS on-resistance - reduces conduction losses and junction temperature rise under continuous 0.7 A load.
Thermal protection	Auto-recovery shutdown with 15 °C hysteresis - prevents permanent damage during sustained overload or poor heatsinking conditions.

Applications

HDD Controller Power Rail

FPGA I/O Bank Supply

Use Scenario: Powering the 1.8 V I/O bank of a Xilinx Spartan-7 FPGA in a portable data acquisition module.

IC Role / Device Role / Timing Role: Primary point-of-load (POL) regulator delivering clean, tightly regulated 1.8 V at up to 0.65 A with minimal board area.

Use Value: Enables use of 2.2 µH inductor and 10 µF ceramic caps - reducing total solution size to <12 mm² while maintaining <10 mV p-p ripple.

Use Scenario: Supplying 1.8 V to the servo-control ASIC in a 2.5-inch hard disk drive.

IC Role / Device Role / Timing Role: Core voltage regulator replacing linear solution to eliminate excessive heat generation in sealed drive enclosure.

Use Value: Achieves >90% efficiency at 500 mA, cutting dissipation from ~450 mW (LDO) to ~70 mW - enabling passive cooling and extending drive MTBF.

Industrial Sensor Node MCU Core

USB-Powered IoT Peripheral

Use Scenario: Generating 1.8 V for ARM Cortex-M4 microcontroller core in a battery-operated vibration sensor node.

IC Role / Device Role / Timing Role: Low-quiescent-current buck converter supporting deep-sleep modes and fast wake-up via EN pin control.

Use Value: 650 µA max IQ allows >3-year battery life on two AA cells; enable pin supports precise power-gating synchronized to sensor sampling intervals.

Use Scenario: Regulating 5 V USB input to stable 1.8 V for BLE radio and flash memory in a compact smart plug.

IC Role / Device Role / Timing Role: Compact, high-frequency POL converter meeting strict EMI limits for Class B consumer devices.

Use Value: 1.7 MHz operation shifts switching noise above AM radio band; small LC values ease filtering and reduce conducted emissions.

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output step-down regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
Texas Instruments TPS62231DRYR	1.8 V fixed, 0.6 A, 3 MHz, 25 µA IQ - higher frequency but lower current rating and no thermal shutdown hysteresis.	Better suited for ultra-low-power wearables; insufficient for sustained 0.7 A HDD loads.	Select if board space is tighter than 2.2 mm × 2.5 mm and peak load ≤0.6 A.
Analog Devices ADP2301AUJZ-1.8-R7	1.8 V fixed, 0.6 A, 700 kHz, 2.5 mA IQ - lower frequency, higher quiescent current, larger inductor requirement.	Requires ≥4.7 µH inductor; less efficient at light loads; better for cost-sensitive industrial controls.	Select if thermal margin is ample and 700 kHz EMI profile aligns with system filters.

Compared with TPS62231DRYR and ADP2301AUJZ-1.8-R7, ST1S12G18R uniquely balances 0.7 A capability, 1.7 MHz operation, <650 µA IQ, and integrated thermal hysteresis - making it optimal for thermally dense, medium-current embedded systems where size, efficiency, and reliability are co-constrained.

Availability

ST1S12G18R is available at Aetrix Electronics and suitable for HDD controller power rails, FPGA I/O banks, industrial sensor node MCUs, and USB-powered IoT peripherals requiring stable component supply, long-lifecycle support, and consistent parametric performance across temperature.

Supply support for ST1S12G18R 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, mixed-signal, power, and microcontroller solutions for automotive, industrial, and consumer markets.

The ST1S12 series belongs to ST's high-efficiency, low-voltage DC-DC converter product line - engineered specifically to replace inefficient linear regulators in space- and thermal-constrained digital core power applications.

FAQ

What is the minimum input voltage required for ST1S12G18R to regulate 1.8 V output?

The ST1S12G18R requires a minimum input voltage of 2.5 V to maintain regulation across its full 0.7 A load range and operating temperature (−40 °C to +125 °C). Below 2.5 V, dropout occurs and output voltage drops linearly with input; the device remains functional but cannot sustain 1.8 V regulation.

Does ST1S12G18R require an external feedback resistor divider?

No. ST1S12G18R has a factory-trimmed internal feedback network that sets the output to exactly 1.8 V - confirmed by the 1.746–1.854 V output voltage specification over temperature. Pin 5 (FB/VO) is internally connected to the 1.8 V reference and requires no external components.

How does the enable (EN) pin behave during power-up and shutdown?

The EN pin is a CMOS-compatible input with 1.5 V turn-on threshold and 0.5 V turn-off threshold. When pulled high (≥1.5 V), the device initiates soft-start and begins switching; when pulled low (<0.5 V), it disables the power switches, halts oscillation, and draws only ≤1 µA. No external pull-up is required for default-enable operation.

Can ST1S12G18R operate reliably at 125 °C junction temperature?

Yes - the device is rated for continuous operation up to +125 °C junction temperature. Thermal shutdown activates at 130–150 °C with 15 °C hysteresis, ensuring safe recovery. Derating is not required at 125 °C, provided PCB copper area and airflow meet the R_thJA = 220 °C/W specification under actual layout conditions.

ST1S12G18R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: SOT-23-5 Thin, TSOT-23-5

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):: 2.5V

Voltage - Input (Max):: 5.5V

Voltage - Output (Min/Fixed):: 1.8V

Voltage - Output (Max):: -

Current - Output:: 700mA

Frequency - Switching:: 1.7MHz

Synchronous Rectifier:: Yes

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: TSOT-23-5

ST1S12G18R FAQ

1.How can I place an order for ST1S12G18R through Aetrix?

Please submit a Request for Quotation (RFQ) for ST1S12G18R 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 ST1S12G18R reliable?

The price and inventory of ST1S12G18R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST1S12G18R is usually 5 days.

3.What payment methods are accepted for ST1S12G18R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST1S12G18R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ST1S12G18R?

ST1S12G18R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ST1S12G18R 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 ST1S12G18R?

For technical support, including ST1S12G18R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST1S12G18R requirements.

6.How does Aetrix verify that ST1S12G18R is sourced from the original manufacturer or authorized distributors?

All ST1S12G18R 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 ST1S12G18R meets industry standards.

7.What is the process for return or replacement of ST1S12G18R?

All ST1S12G18R units undergo pre-shipment inspection (PSI). If there is an issue with ST1S12G18R, 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 ST1S12G18R part is unused and in its original packaging.

Return procedure for ST1S12G18R:

1.Submit a request within 90 days.

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

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