STMicroelectronics LD1117S50CTR

Overview

LD1117S50CTR from STMicroelectronics is a fixed-output 5.0 V, low-dropout linear voltage regulator in SOT-223 package, delivering up to 800 mA output current with 1.1 V typical dropout at 800 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection at 120 Hz. It serves as a primary post-regulator in embedded power rails for microcontrollers and sensors.

For engineers reviewing the LD1117S50CTR datasheet, LD1117S50CTR pinout, LD1117S50CTR application, or LD1117S50CTR equivalent, key selection criteria include dropout voltage under full load, thermal resistance (R_thJA = 110 °C/W), minimum load requirement (2–5 mA), stability with 10 µF ceramic output capacitor, and SOT-223 thermal pad connection to V_OUT.

Technical Context

The LD1117S50CTR uses an NPN pass transistor architecture, enabling high efficiency by routing quiescent current primarily into the load rather than ground-unlike PNP-based regulators. Its internal bandgap reference and error amplifier maintain regulation across input voltages from 6.5 V to 15 V.

Thermal protection and current limiting are implemented on-die, with junction temperature operating range of −40 °C to +125 °C (C-grade). The device achieves ±1 % initial accuracy via laser trimming and sustains ≤0.5 % temperature-induced drift over full operating range.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal tab electrically connected to V_OUT; requires PCB copper area for thermal dissipation. Pin 1 = IN, Pin 2 = OUT, Pin 3 = GND, Pin 4 = TAB/V_OUT.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AMS1117-5.0 and TLV1117-50, the LD1117S50CTR offers superior thermal performance (R_thJA = 110 °C/W), higher PSRR, and broader industrial temperature support (−40 to +125 °C), making it optimal for high-reliability embedded power rails where stability under thermal stress is critical.

Availability

LD1117S50CTR is available at Aetrix Electronics and suitable for industrial control systems, automotive body electronics, medical sensor modules, and IoT edge nodes requiring stable component supply with long-term manufacturability.

Supply support for LD1117S50CTR 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The LD1117 series belongs to ST's broad portfolio of linear voltage regulators designed for cost-effective, thermally robust post-regulation in space-constrained embedded systems-emphasizing reliability, ease of use, and wide operating temperature support.

FAQ

What is the minimum input voltage required for stable 5.0 V output at 800 mA?

The LD1117S50CTR requires a minimum input voltage of 6.1 V to maintain regulation at 800 mA load, based on its 1.1 V typical dropout voltage. At elevated temperatures or worst-case process corners, design margin should allow for up to 1.3 V dropout, so 6.3 V is recommended for robust operation across full temperature and lifetime conditions.

Can the LD1117S50CTR be used without an output capacitor?

No. A minimum 10 µF ceramic output capacitor is mandatory for stability per the datasheet. Omitting it causes oscillation and output voltage collapse under load. The capacitor must be placed within 5 mm of the OUT and GND pins, with low-ESR X5R or X7R dielectric; tantalum or aluminum electrolytics are not recommended due to ESR sensitivity.

Is the thermal tab (Pin 4) electrically isolated or connected internally?

The SOT-223 thermal tab (Pin 4) is electrically connected to the V_OUT pin internally. It must be soldered to a PCB copper pour tied to the 5 V output net-not to ground-to ensure proper thermal conduction and avoid short circuits. This configuration also improves transient response by lowering output impedance.

How does the LD1117S50CTR handle reverse-voltage conditions on the input or output?

The LD1117S50CTR has no reverse-voltage protection. Applying reverse polarity to IN or OUT can cause destructive latch-up or junction breakdown. External protection-such as a series Schottky diode on the input (with ~0.3 V drop) or a reverse-biased diode from OUT to IN-is required in systems prone to battery reversal or hot-swap events.