STMicroelectronics

LD1117S18TR - 1.8V Fixed 800mA LDO Regulator | STMicroelectronics

Name: LD1117S18TR
Brand: STMicroelectronics
Price: 0.35 USD
Availability: InStock

MPN: LD1117S18TR ✓ Active

In Stock (99,999) Ships in 1-3 business days

1.8 V Vdss 800 mA Id 50 °C/W Rds(on) SOT-223 Package

$0.35 USD / Unit

MOQ: 1 |

Volume Pricing

Qty	Unit Price	Extended
1	$0.35	$0.35
10	$0.28	$2.80
100	$0.22	$22.00
500	$0.18	$90.00
1,000	$0.15	$150.00

ℹ️ All prices are in USD

View Datasheet (PDF) View Alternatives

Quantity

Drop-in alternatives for LD1117S18TR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.

Quick Comparison Tool — Select alternative parts for side-by-side comparison:

LD1117S33TR

✅ Drop-In

STMicroelectronics

📦 SOT-223

Fixed · 3.3 V · 800 mA · Up to 15 V · 1.1 V typical at 800 mA · 0.2 % typical · 0.4 % typical · 5 mA typical

✓ 99,999 In Stock

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LD1117S12TR

✅ Drop-In

📦 SOT-223

Same package and pinout, but output voltage is 1.2V instead of 1.8V

📋 Reference alternative (not in catalog)

LD1117S25TR

✅ Drop-In

STMicroelectronics

📦 SOT-223

Fixed · 2.5 V · 800 mA · Up to 15 V · 1.1 V at 800 mA · 5 mA · 0.2% (typical) · 0.4% (typical)

✓ 99,999 In Stock

$0.18 / Unit

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AMS1117-1.8

✅ Drop-In

📦 SOT-223

Cross-brand, same package and pinout, output current up to 1A

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NCP1117ST18T3G

✅ Drop-In

📦 SOT-223

Cross-brand, same package and pinout, output current up to 1A

📋 Reference alternative (not in catalog)

AP1117-18

✅ Drop-In

📦 SOT-223

Cross-brand, same package and pinout, output current up to 1A

📋 Reference alternative (not in catalog)

LD1117S18TR Maximum Ratings & Electrical Characteristics

Output Type	Fixed
Output Voltage	1.8 V
Maximum Output Current	800 mA
Input Voltage Range	2.5 V to 15 V
Dropout Voltage	1.1 V at 800 mA
Quiescent Current	5 mA
Line Regulation	0.2% (typical)
Load Regulation	0.4% (typical)
Thermal Resistance (junction-to-ambient)	50 °C/W
Operating Temperature Range	-40°C to +125°C
Package	SOT-223
Mounting Type	Surface Mount
MSL Level	1 (unlimited)
RoHS Status	Compliant
Enable Pin	No

LD1117S18TR Pin Configuration

Pin 1	GND — Ground
Pin 2	VOUT — Regulated output voltage (1.8V)
Pin 3	VIN — Input supply voltage
Pin 4	TAB — Exposed pad, connected to VOUT

Safe Operating Area (SOA) & Thermal Characteristics

No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.

Typical Applications

LD1117S18TR is suitable for 6 applications: Microcontroller Power Supply, FPGA Core Voltage, Battery-Powered IoT Devices, Post-Regulation in Switching Power Supplies, Industrial Control Systems, Consumer Electronics.

🔧

Microcontroller Power Supply

The LD1117S18TR provides a stable 1.8V supply for microcontrollers that operate at this voltage, such as STM32L series. Its low dropout voltage and 800mA output current ensure reliable operation even when the input voltage is close to 1.8V. The SOT-223 package is compact and suitable for space-constrained designs. The low quiescent current of 5mA helps extend battery life in portable applications. The device's thermal shutdown protection prevents damage from overheating, ensuring long-term reliability.

Recommended

STM32L053R8 (Microcontroller requiring 1.8V supply) STM32L476RG (Microcontroller requiring 1.8V supply)

🔧

FPGA Core Voltage

Many FPGAs require a 1.8V core voltage, and the LD1117S18TR can provide this with low noise and good regulation. The device's 800mA output current is sufficient for small to medium FPGAs. The low dropout voltage allows operation from a 3.3V rail with adequate headroom. The SOT-223 package is easy to solder and fits on standard PCB footprints. The internal current limiting protects the FPGA from overcurrent conditions. The device's thermal shutdown ensures safe operation under high ambient temperatures.

Recommended

ICE40LP1K (FPGA requiring 1.8V core) LCMXO2-1200 (FPGA requiring 1.8V core)

🧩

Battery-Powered IoT Devices

The LD1117S18TR is ideal for battery-powered IoT devices that require a stable 1.8V supply. Its low quiescent current of 5mA helps conserve battery power, extending device runtime. The wide input voltage range of 2.5V to 15V allows operation from various battery configurations, such as two AA batteries or a single lithium-ion cell. The SOT-223 package is compact and lightweight, making it suitable for wearable and portable devices. The device's thermal shutdown and current limiting provide protection in harsh environments.

Recommended

ESP32 (IoT module requiring 1.8V supply) nRF52832 (BLE SoC requiring 1.8V supply)

⚡

Post-Regulation in Switching Power Supplies

The LD1117S18TR can be used as a post-regulator after a switching power supply to reduce ripple and noise. Its low dropout voltage and high PSRR ensure a clean 1.8V output. The device's 800mA output current is sufficient for many digital loads. The SOT-223 package allows for easy integration into existing power supply designs. The internal current limiting and thermal shutdown provide additional protection. The device's stability with ceramic capacitors simplifies the output filter design.

Recommended

LM2596 (Switching regulator providing intermediate voltage) TPS5430 (Switching regulator providing intermediate voltage)

🏭

Industrial Control Systems

The LD1117S18TR is suitable for industrial control systems that require a reliable 1.8V supply for logic circuits and sensors. Its wide input voltage range and robust protection features make it suitable for harsh industrial environments. The device's operating temperature range of -40°C to +125°C ensures reliable operation in extreme conditions. The SOT-223 package is rugged and can withstand vibration and thermal cycling. The low dropout voltage allows operation from a 3.3V rail with minimal power loss.

Recommended

STM32F103 (Industrial microcontroller requiring 1.8V supply) MSP430G2553 (Industrial microcontroller requiring 1.8V supply)

📺

Consumer Electronics

The LD1117S18TR is used in consumer electronics such as set-top boxes, routers, and gaming consoles to provide a stable 1.8V supply for various ICs. Its low cost and small footprint make it ideal for high-volume production. The device's low quiescent current helps meet energy efficiency standards. The SOT-223 package is compatible with standard reflow soldering processes. The device's thermal shutdown and current limiting protect the product from damage due to faults.

Recommended

MT7628 (Router SoC requiring 1.8V supply) RT5350 (Router SoC requiring 1.8V supply)

Recommended Products Summary

STM32L053R8 Microcontroller requiring 1.8V supply Used in: Microcontroller Power Supply STM32L476RG Microcontroller requiring 1.8V supply Used in: Microcontroller Power Supply ICE40LP1K FPGA requiring 1.8V core Used in: FPGA Core Voltage LCMXO2-1200 FPGA requiring 1.8V core Used in: FPGA Core Voltage ESP32 IoT module requiring 1.8V supply Used in: Battery-Powered IoT Devices nRF52832 BLE SoC requiring 1.8V supply Used in: Battery-Powered IoT Devices LM2596 Switching regulator providing intermediate voltage Used in: Post-Regulation in Switching Power Supplies TPS5430 Switching regulator providing intermediate voltage Used in: Post-Regulation in Switching Power Supplies STM32F103 Industrial microcontroller requiring 1.8V supply Used in: Industrial Control Systems MSP430G2553 Industrial microcontroller requiring 1.8V supply Used in: Industrial Control Systems MT7628 Router SoC requiring 1.8V supply Used in: Consumer Electronics RT5350 Router SoC requiring 1.8V supply Used in: Consumer Electronics

What is the output voltage of LD1117S18TR?

The LD1117S18TR provides a fixed output voltage of 1.8V. According to the STMicroelectronics LD1117 datasheet, the output voltage is set internally to 1.8V with an accuracy of ±2%.

What is the maximum output current of LD1117S18TR?

The LD1117S18TR can deliver a maximum output current of 800mA. This is specified in the STMicroelectronics LD1117 datasheet, which lists the output current range from 0mA to 800mA.

What is the dropout voltage of LD1117S18TR?

The dropout voltage of the LD1117S18TR is 1.1V at 800mA output current. This means the input voltage must be at least 1.1V higher than the output voltage to maintain regulation.

What is the input voltage range of LD1117S18TR?

The LD1117S18TR operates with an input voltage range from 2.5V to 15V. This wide range allows it to be used in various applications, from battery-powered devices to industrial power supplies.

What is the quiescent current of LD1117S18TR?

The quiescent current of the LD1117S18TR is 5mA. This is the current consumed by the regulator itself when no load is applied, and it is important for battery-powered applications where power consumption is critical.

What package is LD1117S18TR available in?

The LD1117S18TR is available in the SOT-223 package. This surface-mount package is compact and suitable for automated assembly, with a thermal resistance of 50°C/W.

Is LD1117S18TR RoHS compliant?

Yes, the LD1117S18TR is RoHS compliant. According to the STMicroelectronics product page, the device meets the requirements of the RoHS directive, which restricts the use of hazardous substances in electrical and electronic equipment.

What are the typical applications of LD1117S18TR?

The LD1117S18TR is commonly used in applications requiring a stable 1.8V supply, such as powering microcontrollers, FPGAs, and other digital ICs. It is also used in battery-powered devices, IoT devices, and post-regulation in switching power supplies.

Does LD1117S18TR have thermal shutdown protection?

Yes, the LD1117S18TR includes internal thermal shutdown protection. This feature prevents the device from overheating by shutting down the output when the junction temperature exceeds a safe limit, protecting the regulator and the load.

What is the difference between LD1117S18TR and LD1117S33TR?

The LD1117S18TR outputs a fixed 1.8V, while the LD1117S33TR outputs a fixed 3.3V. Both are in the same LD1117 family and share the same SOT-223 package and pinout, making them drop-in replacements for each other if the output voltage requirement changes.

Can LD1117S18TR be used in automotive applications?

The LD1117S18TR is not specifically qualified to AEC-Q100, so it is not recommended for automotive applications that require such qualification. For automotive-grade LDOs, consider STMicroelectronics' AEC-Q100 qualified parts like the L4931 series.

What is the price of LD1117S18TR?

As of 2026-08-07, the price of LD1117S18TR is approximately $0.35 for a single unit, $0.22 for 100 units, and $0.15 for 1000 units, based on distributor listings. Prices may vary by quantity and supplier.

Where can I buy LD1117S18TR?

The LD1117S18TR is available from major distributors such as DigiKey, Mouser, and Arrow. You can also purchase it directly from STMicroelectronics' authorized distributors. Check stock availability and pricing on their websites.

What is the lead time for LD1117S18TR?

The lead time for LD1117S18TR is typically 4-6 weeks for standard orders, but it can vary depending on the distributor and current market conditions. For urgent requirements, check with distributors for expedited shipping options.

Is LD1117S18TR in stock?

Stock availability for LD1117S18TR varies by distributor. As of 2026-08-07, DigiKey and Mouser typically have stock, but it is recommended to check their websites for real-time inventory and lead times.

What is the best drop-in replacement for LD1117S18TR?

The best drop-in replacement for LD1117S18TR is the AMS1117-1.8 from Advanced Monolithic Systems, which shares the same SOT-223 package and pinout. Other options include the NCP1117ST18T3G from onsemi and the AP1117-18 from Diodes Incorporated, both pin-compatible and with similar specifications.

Can AMS1117-1.8 replace LD1117S18TR?

Yes, the AMS1117-1.8 can replace the LD1117S18TR as it is pin-compatible and has the same SOT-223 package. The AMS1117-1.8 has a similar output voltage (1.8V) and maximum output current (1A), making it a suitable drop-in replacement.

What is the difference between LD1117S18TR and AMS1117-1.8?

The LD1117S18TR has a maximum output current of 800mA, while the AMS1117-1.8 can deliver up to 1A. Both are fixed 1.8V LDOs in SOT-223 packages, but the AMS1117-1.8 has a slightly higher current capability and a lower dropout voltage of 1.1V at 800mA.

Where can I download the LD1117S18TR datasheet PDF?

The LD1117S18TR datasheet PDF can be downloaded from the STMicroelectronics website at https://www.st.com/resource/en/datasheet/ld1117.pdf. It is also available on distributor websites like DigiKey and Mouser.

What are the key specifications of LD1117S18TR that engineers should know?

The key specifications of LD1117S18TR include a fixed 1.8V output, 800mA maximum output current, 1.1V dropout voltage at full load, 5mA quiescent current, and an input voltage range of 2.5V to 15V. It is packaged in SOT-223 and operates over -40°C to +125°C.

Engineering reference data for LD1117S18TR — comparison, design guidance, and compliance information.

Selection Guide

Choose the LD1117S18TR when you need a fixed 1.8V output with up to 800mA current capability in a compact SOT-223 package. It is ideal for powering microcontrollers, FPGAs, and other digital ICs that require a stable 1.8V supply. If you need a higher output current of 1A, consider the AMS1117-1.8 or NCP1117ST18T3G, which are pin-compatible drop-in replacements. For applications requiring a different output voltage, such as 3.3V, the LD1117S33TR is a same-brand alternative with the same package and pinout. The LD1117S18TR is a cost-effective choice for consumer and industrial applications where STMicroelectronics' reliability is valued.

Comparison with Alternatives

Parameter	This Product	LD1117S33TR	AMS1117-1.8	NCP1117ST18T3G
Package	SOT-223	SOT-223	SOT-223	SOT-223
Brand	STMicroelectronics	STMicroelectronics	Advanced Monolithic Systems	onsemi
Output Voltage	1.8V	3.3V	1.8V	1.8V
Maximum Output Current	800mA	800mA	1A	1A
Dropout Voltage	1.1V at 800mA	1.1V at 800mA	1.1V at 800mA	1.1V at 800mA
Quiescent Current	5mA	5mA	5mA	5mA
Input Voltage Range	2.5V to 15V	2.5V to 15V	2.5V to 15V	2.5V to 15V
Enable Pin	No	No	No	No

Key Differentiators

Fixed 1.8V output with 800mA capability (vs AMS1117-1.8)
STMicroelectronics quality and reliability (vs AP1117-18)
Wide input voltage range (vs NCP1117ST18T3G)

Design Notes

The LD1117S18TR in SOT-223 has a thermal resistance of 50°C/W. At maximum output current of 800mA and a dropout voltage of 1.1V, power dissipation is approximately 0.88W, resulting in a temperature rise of 44°C above ambient. Ensure adequate PCB copper area for heat dissipation, especially in high ambient temperature environments.

Place input and output capacitors close to the respective pins. A 10uF tantalum or ceramic capacitor on the input and a 10uF capacitor on the output are recommended for stability. The SOT-223 package has a large tab connected to VOUT, which should be soldered to a large copper pad for thermal and electrical performance.

Do not exceed the maximum input voltage of 15V. Ensure the input voltage is at least 1.1V above the output voltage to maintain regulation. The device does not have an enable pin, so power sequencing must be handled externally if required. Use a capacitor with low ESR on the output to avoid oscillation.