STMicroelectronics LD1117S12TR

Overview

LD1117S12TR from STMicroelectronics is a fixed-output 1.2 V low-dropout linear voltage regulator in SOT-223 package, delivering up to 800 mA output current with 1.0 V typical dropout at 100 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection at 120 Hz - used for post-regulation of 3.3 V or 5 V rails in embedded microcontroller power supplies.

For engineers reviewing the LD1117S12TR datasheet, LD1117S12TR pinout, LD1117S12TR application, or LD1117S12TR equivalent, key selection criteria include dropout performance under 800 mA load, thermal resistance (R_thJA = 110 °C/W), minimum 10 µF output capacitor requirement, and compatibility with standard SOT-223 PCB footprints across industrial and automotive control modules.

Technical Context

The LD1117S12TR uses an NPN pass transistor architecture to minimize quiescent current consumption in the load path, enabling high efficiency at light loads. Its internal bandgap reference and error amplifier maintain regulation across input voltages from 2.2 V to 15 V while sustaining stable operation with only a 10 µF ceramic or tantalum output capacitor.

Thermal protection and current limiting are implemented on-die, with junction temperature operating range specified from −40 °C to +125 °C for the 'C' grade variant. The device achieves ±1 % initial output accuracy at 25 °C and maintains ≤0.5 % temperature stability over full operating range.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal pad connected internally to V_OUT; 3-pin configuration optimized for surface-mount assembly and thermal dissipation in compact power rails.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-1202E/TT and TLV1117-12CDCYR, the LD1117S12TR uniquely balances 800 mA capability, ±1 % accuracy, and SOT-223 manufacturability - making it optimal for cost-sensitive, thermally constrained industrial controllers requiring tight core voltage regulation.

Availability

LD1117S12TR is available at Aetrix Electronics and suitable for industrial PLCs, automotive body control units, medical wearable sensor hubs, and smart home edge nodes requiring stable component supply with long-term lifecycle assurance.

Supply support for LD1117S12TR 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, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The LD1117 series belongs to ST's high-reliability linear regulator product line, engineered specifically for robust post-regulation in harsh environments where thermal resilience, accuracy, and long-term stability are critical.

FAQ

What is the minimum input voltage required for stable 1.2 V output at 800 mA?

The LD1117S12TR requires a minimum input voltage of 2.2 V to maintain regulation at 800 mA, based on its maximum dropout voltage of 1.2 V at that load (per Table 3, TJ = 0–125 °C). At room temperature and 100 mA, dropout drops to 1.0 V typ., allowing operation down to 2.2 V input.

Can LD1117S12TR replace adjustable LD1117 variants in existing designs?

No - the LD1117S12TR is a fixed 1.2 V version with only three terminals (VIN, GND, VOUT); it lacks the ADJ pin found on adjustable variants. Substitution would require redesigning the feedback network and verifying stability with the new output impedance profile.

Is a bypass capacitor required on the adjustment pin for LD1117S12TR?

Not applicable - the LD1117S12TR has no adjustment pin. It is a fixed-output variant. Only input (≥1 µF) and output (≥10 µF) capacitors are required, with the latter needing low ESR for guaranteed stability per Section 5 of the datasheet.

How does thermal performance differ between SOT-223 and DPAK packages for LD1117S12TR?

The SOT-223 package has R_thJA = 110 °C/W, while DPAK (TO-252) offers R_thJA = 100 °C/W - a 10 °C/W improvement. However, DPAK requires larger PCB area and different footprint; SOT-223 remains preferred for high-density layouts where thermal margin is managed via copper pour.