LD1117ADJTR - 1A Low Dropout Positive Regulator | STMicroelectronics
MPN: LD1117ADJTR β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.35 | $0.35 |
| 10 | $0.3 | $3.00 |
| 100 | $0.25 | $25.00 |
| 500 | $0.2 | $100.00 |
| 1,000 | $0.18 | $180.00 |
LD1117ADJTR Overview
A low dropout regulator (LDO) is a type of linear voltage regulator that maintains a stable output voltage even when the input voltage is very close to the output voltage. LDOs are essential in power management systems where a clean, regulated supply is needed with minimal voltage headroom. They are part of the voltage regulator family, which also includes switching regulators, and are widely used in battery-powered devices, automotive electronics, and industrial control systems.
Key features of the LD1117ADJTR include a fixed or adjustable output, internal current limiting, and thermal shutdown protection. The device operates over a junction temperature range of 0Β°C to 125Β°C, making it suitable for a variety of environments. The SOT-223 package offers a compact footprint with a thermal pad for improved heat dissipation, enabling reliable operation at moderate power levels.
The LD1117ADJTR uses a PNP pass transistor architecture, which provides low dropout voltage and stable operation. The adjustable version uses an external resistor divider to set the output voltage, allowing flexibility in design. The device also features a low quiescent current, which is beneficial for battery-powered applications where power efficiency is critical.
Typical applications include post-regulation for switching power supplies, battery chargers, and as a local supply for microcontrollers and other digital ICs. The wide input voltage range and low dropout make it ideal for automotive and industrial applications where input voltage can vary significantly.
When designing with the LD1117ADJTR, ensure adequate input-to-output voltage headroom to maintain regulation. The thermal pad should be connected to a large copper area for heat dissipation. Proper decoupling capacitors on input and output are essential for stability and transient response.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the STMicroelectronics datasheet, providing a comprehensive resource for engineers.
Drop-in alternatives for LD1117ADJTR β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
LD1117ADJTR-ND
β Drop-Inπ Reference alternative (not in catalog)
AMS1117ADJ
β Drop-Inπ Reference alternative (not in catalog)
NCP1117ADJ
β Drop-Inπ Reference alternative (not in catalog)
LD1117ADJTR Maximum Ratings & Electrical Characteristics
| Output Type | Adjustable |
| Output Voltage Range | 1.25 V to 15 V |
| Maximum Output Current | 1 A |
| Input Voltage Range | Up to 15 V |
| Dropout Voltage | 1.1 V at 1 A |
| Line Regulation | 0.2 % (typical) |
| Load Regulation | 0.4 % (typical) |
| Quiescent Current | 5 mA (typical) |
| Operating Temperature Range | 0Β°C to 125Β°C |
| Package | SOT-223 |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited) |
| RoHS Status | Compliant |
| Thermal Shutdown | Yes |
| Current Limiting | Yes |
LD1117ADJTR Pin Configuration
| Pin 1 | ADJ β Adjustable pin for setting output voltage |
| Pin 2 | OUT β Regulated output voltage |
| Pin 3 | IN β Input supply voltage |
| Pin 4 | TAB β Thermal pad, connected to ground |
Typical Applications
LD1117ADJTR is suitable for 6 applications: Post-Regulation for Switching Power Supplies, Battery-Powered Devices, Automotive Electronics, Industrial Control Systems, Consumer Electronics, Telecommunication Equipment.
Post-Regulation for Switching Power Supplies
The LD1117ADJTR is used as a post-regulator to provide a clean, low-noise output from a switching power supply. Its low dropout voltage allows it to operate efficiently with minimal headroom, and its adjustable output enables precise voltage setting. In a typical application, the LD1117ADJTR is placed after a buck converter to reduce ripple and provide a stable voltage for sensitive loads. The input capacitor (10uF) and output capacitor (22uF) are essential for stability and transient response. The thermal pad should be connected to a large copper area to dissipate heat generated by the dropout voltage. Compared to using a switching regulator alone, the LDO eliminates switching noise but dissipates more power; for a 5V-to-3.3V conversion at 500mA, power dissipation is 0.85W, which is manageable with proper PCB layout.
Recommended
Battery-Powered Devices
The LD1117ADJTR is ideal for battery-powered devices due to its low dropout voltage and low quiescent current. It can regulate the battery voltage down to a stable level for microcontrollers, sensors, and wireless modules. In a typical application, the LD1117ADJTR is connected directly to a lithium-ion battery (3.7V nominal) and provides a 3.3V output. The low dropout of 1.1V ensures the regulator operates even when the battery voltage drops to 4.4V. The quiescent current of 5mA is acceptable for many applications, but for ultra-low-power designs, a regulator with lower quiescent current may be preferred. The adjustable output allows optimization for different battery chemistries and load requirements.
Recommended
Automotive Electronics
The LD1117ADJTR is used in automotive electronics for powering sensors, microcontrollers, and communication interfaces. Its wide input voltage range and thermal shutdown protection make it suitable for the harsh automotive environment. In a typical application, the LD1117ADJTR regulates the vehicle's 12V battery voltage down to 5V or 3.3V for logic circuits. The dropout voltage of 1.1V ensures operation even when the battery voltage drops during cranking. The thermal shutdown prevents damage from overheating in high-temperature environments. However, the operating temperature range of 0Β°C to 125Β°C may not be sufficient for all automotive applications, which often require -40Β°C to 125Β°C. For such applications, consider the LD1117ADJTR-Q1 variant with extended temperature range.
Recommended
Industrial Control Systems
The LD1117ADJTR is widely used in industrial control systems for powering PLCs, sensors, and actuators. Its robust design and thermal protection ensure reliable operation in industrial environments. In a typical application, the LD1117ADJTR provides a stable 5V supply for a microcontroller from a 24V industrial bus. The wide input voltage range allows direct connection to the bus, but power dissipation must be considered. For a 24V-to-5V conversion at 100mA, power dissipation is 1.9W, which requires a heatsink or large copper area. The adjustable output allows customization for different logic levels. The device's current limiting and thermal shutdown provide protection against faults.
Recommended
Consumer Electronics
The LD1117ADJTR is used in consumer electronics such as set-top boxes, routers, and gaming consoles to provide clean power rails for various ICs. Its low cost and availability make it a popular choice for high-volume production. In a typical application, the LD1117ADJTR regulates a 5V rail down to 3.3V for a system-on-chip. The low dropout voltage ensures efficient operation, and the SOT-223 package is easy to assemble. The adjustable output allows fine-tuning of the supply voltage for optimal performance. The device's thermal shutdown protects against overheating in compact enclosures.
Recommended
Telecommunication Equipment
The LD1117ADJTR is used in telecommunication equipment for powering line drivers, transceivers, and baseband processors. Its low noise and stable output are essential for communication signal integrity. In a typical application, the LD1117ADJTR provides a clean 3.3V supply for an Ethernet PHY. The low dropout voltage ensures operation from a 5V rail with minimal power loss. The adjustable output allows optimization for different PHY requirements. The device's thermal shutdown protects against overheating in densely packed equipment. For high-frequency applications, additional filtering may be required to reduce noise.
Recommended
Recommended Products Summary
Engineering reference data for LD1117ADJTR β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LD1117ADJTR-ND | AMS1117ADJ | NCP1117ADJ |
|---|---|---|---|---|
| Package | SOT-223 | SOT-223 - same | SOT-223 - same | SOT-223 - same |
| Output Current | 1 A | 1 A | 1 A | 1 A |
| Output Voltage Range | 1.25V to 15V | 1.25V to 15V | 1.25V to 13.8V | 1.25V to 18V |
| Dropout Voltage | 1.1V at 1A | 1.1V at 1A | 1.1V at 1A | 1.1V at 1A |
| Quiescent Current | 5 mA | 5 mA | 5 mA | 5 mA |
| Operating Temperature Range | 0Β°C to 125Β°C | 0Β°C to 125Β°C | -40Β°C to 125Β°C | -40Β°C to 125Β°C |
| Line Regulation | 0.2% | 0.2% | 0.2% | 0.2% |
| Load Regulation | 0.4% | 0.4% | 0.4% | 0.4% |
Key Differentiators
- Wide output voltage range up to 15V (vs AMS1117ADJ)
- Extended temperature range option (vs NCP1117ADJ)
- Proven STMicroelectronics quality (vs AMS1117ADJ)
Design Notes
The LD1117ADJTR in SOT-223 package has a thermal resistance of approximately 50Β°C/W (junction-to-ambient) with minimal copper area. For a 12V-to-5V conversion at 500mA, power dissipation is 3.5W, resulting in a temperature rise of 175Β°C, which exceeds the maximum junction temperature. Use a larger copper area or a heatsink to keep the junction temperature below 125Β°C. For continuous operation above 1W, ensure the thermal pad is soldered to a large ground plane.
Place input and output capacitors as close to the IC pins as possible. Use a 10uF ceramic capacitor on the input and a 22uF ceramic capacitor on the output for stability. Add a 0.1uF ceramic capacitor in parallel for high-frequency noise bypass. The thermal pad should be connected to a large copper area with multiple vias to improve heat dissipation.
Do not exceed the maximum input voltage of 15V. Ensure the external resistor divider uses 1% or better tolerance resistors to maintain output voltage accuracy. The adjust pin current (IADJ) is typically 60uA, which should be considered when calculating the output voltage. Avoid using the device without output capacitor, as it may oscillate.
Compliance Information
RoHS compliant per STMicroelectronics product page. Not AEC-Q100 qualified - choose LD1117ADJTR-Q1 for automotive.
