STMicroelectronics LD1117S33CTR

Overview

LD1117S33CTR from STMicroelectronics is a fixed-output 3.3 V, 800 mA low-dropout linear voltage regulator in SOT-223 package, featuring 1 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 switching supplies in industrial control modules and embedded microcontroller power rails.

For engineers reviewing the LD1117S33CTR datasheet, LD1117S33CTR pinout, LD1117S33CTR application, or LD1117S33CTR equivalent, key selection criteria include dropout voltage under load, thermal resistance (R_thJA = 110 °C/W), output tolerance across temperature, minimum load current requirement (2–5 mA), and compatibility with standard 10 µF ceramic output capacitors.

Technical Context

The LD1117S33CTR uses an NPN pass transistor architecture to minimize quiescent current consumption in the load path, enabling higher efficiency than PNP-based LDOs. Its internal bandgap reference and error amplifier maintain regulation across input voltages from 4.75 V to 15 V and junction temperatures from −40 °C to +125 °C.

On-chip trimming achieves ±1 % initial output accuracy at 25 °C, while thermal regulation (0.01–0.1 %/W) and long-term stability (0.3 % over 1000 hrs at 125 °C) ensure consistent performance in thermally demanding environments such as motor drive PCBs and programmable logic controllers.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal pad connected internally to V_OUT; compact 3.4 mm × 6.5 mm footprint optimized for space-constrained industrial PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AMS1117-3.3 and TLV1117-33, the LD1117S33CTR delivers superior output accuracy (±1 % vs. ±2 %), lower thermal resistance (110 vs. ≥125 °C/W), and proven robustness in industrial temperature cycling - making it optimal for mission-critical embedded power rails requiring long-term stability.

Availability

LD1117S33CTR is available at Aetrix Electronics and suitable for industrial PLCs, embedded microcontroller power supplies, smart sensor nodes, and motor drive control boards requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for LD1117S33CTR 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, specializing in power management, microcontrollers, and automotive-grade ICs with ISO 9001-certified manufacturing.

The LD1117 series belongs to ST's general-purpose linear regulator product line, designed specifically for cost-sensitive yet thermally demanding industrial and embedded applications requiring high reliability and wide-input-voltage operation.

FAQ

What is the minimum load current required for stable regulation?

The LD1117S33CTR requires a minimum load current of 2–5 mA to maintain regulation, as specified in Table 3 and Table 12 of the datasheet. This is achieved by placing a 1 kΩ–2.2 kΩ pull-down resistor from V_OUT to GND when driving very light or intermittent loads, such as standby logic or EEPROM interfaces.

Can the LD1117S33CTR be used with ceramic output capacitors?

Yes - the LD1117S33CTR is stable with standard 10 µF X5R/X7R ceramic capacitors (ESR < 1 Ω), eliminating the need for higher-ESR tantalum or aluminum electrolytic types. This reduces board area, improves reliability, and avoids aging-related capacitance drift in long-life industrial deployments.

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

In SOT-223, R_thJA is 110 °C/W; in DPAK (TO-252), it drops to 100 °C/W - a 9 % improvement. However, DPAK requires larger PCB real estate and different footprint layout. For 800 mA loads above 60 °C ambient, DPAK enables higher power density without forced air cooling, whereas SOT-223 demands aggressive copper pour design.

Is the LD1117S33CTR compatible with lead-free reflow profiles?

Yes - the LD1117S33CTR is qualified for standard lead-free reflow per JEDEC J-STD-020, with peak temperature up to 260 °C for 30 seconds. The SOT-223 package uses matte tin plating and passes MSL3 moisture sensitivity testing, ensuring robust assembly yield in high-volume SMT lines.