STMicroelectronics LD1117D33CTR

Overview

LD1117D33CTR from STMicroelectronics is a fixed-output 3.3 V low-dropout linear voltage regulator delivering up to 800 mA, 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 in microcontroller power rails, USB peripheral supplies, and industrial sensor interfaces.

For engineers reviewing the LD1117D33CTR datasheet, LD1117D33CTR pinout, LD1117D33CTR application, or LD1117D33CTR equivalent, this page delivers verified electrical specs, thermal performance data, SOT-223 package layout, real-world load/line regulation behavior, and validated alternatives for 3.3 V LDO replacement in cost-sensitive embedded designs.

Technical Context

The LD1117D33CTR 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 tight output regulation across temperature and load.

It integrates thermal shutdown and current limiting, with on-chip trimming achieving ±1 % output accuracy at 25 °C and ±2 % over −40 to +125 °C (C-grade). Stability requires only a 10 µF ceramic or tantalum output capacitor, eliminating need for complex compensation networks.

Key Specifications

Pinout & Package

SOT-223 package (4-pin, tab-connected to V_OUT), optimized for surface-mount assembly and thermal performance in space-constrained PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3.3 V LDO regulator applications.

Compared with AMS1117-3.3 and TLV1117-33CDCYR, the LD1117D33CTR offers superior thermal resistance in SOT-223 (110 °C/W vs. >130 °C/W for SO-8), guaranteed ±1 % accuracy at 25 °C, and broader package availability - making it optimal for thermally constrained industrial and embedded applications demanding long-term stability.

Availability

LD1117D33CTR is available at Aetrix Electronics and suitable for microcontroller power supplies, USB peripheral regulation, and industrial sensor interfaces requiring stable component supply with consistent parametric performance across production batches.

Supply support for LD1117D33CTR 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 analog ICs for industrial, automotive, and consumer markets.

The LD1117 series belongs to ST's general-purpose linear regulator product line, designed specifically for cost-sensitive, high-volume embedded systems needing reliable, easy-to-use 3.3 V and other fixed-voltage regulation with minimal external components.

FAQ

What is the minimum input voltage required for stable 3.3 V output at 800 mA?

The LD1117D33CTR requires a minimum input voltage of 4.4 V to maintain regulation at 800 mA, based on its maximum dropout voltage of 1.2 V (per Table 12, TJ = 0 to 125 °C). At lower loads, input can drop to 4.3 V (1.1 V dropout), but design margin should include worst-case thermal and tolerance conditions.

Can the LD1117D33CTR be used with ceramic output capacitors?

Yes - the LD1117D33CTR is stable with ceramic capacitors ≥10 µF, provided they meet the minimum ESR requirement (typically >15 mΩ). ST's datasheet explicitly validates stability with standard X5R/X7R ceramics, eliminating need for tantalum or aluminum electrolytic types.

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 10 °C/W improvement due to larger thermal pad area. For 800 mA at 3 V dropout (2.4 W dissipation), DPAK yields ~24 °C lower junction rise above ambient, enabling higher ambient operation without heatsink.

Is there a version with enhanced ESD protection for industrial I/O applications?

No - the LD1117D33CTR has standard HBM ESD rating (2 kV per JEDEC JESD22-A114), not enhanced industrial-grade (e.g., 4 kV+). For high-ESD environments, ST recommends adding external TVS diodes on input/output lines; alternative parts like STLQ015 (ultra-low IQ LDO) offer higher ESD but lack 800 mA capability.