STMicroelectronics LD1117DT33

Overview

LD1117DT33 from STMicroelectronics is a fixed-output 3.3 V low-dropout linear voltage regulator 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-used for post-regulation in industrial power supplies and embedded microcontroller core rails.

For engineers reviewing the LD1117DT33 datasheet, LD1117DT33 pinout, LD1117DT33 application, or LD1117DT33 equivalent, this page provides verified package mapping (TO-252/DPAK), thermal resistance data (R_thJA = 100 °C/W), minimum load requirement (2–5 mA), stability capacitor value (10 µF), and validated alternatives for 3.3 V LDO replacement in cost-sensitive, thermally constrained designs.

Technical Context

The LD1117DT33 employs 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 trimming circuitry achieve tight initial accuracy without external components.

It integrates thermal shutdown and current limiting, operates across –40 °C to +125 °C junction temperature, and maintains regulation with input-to-output differentials as low as 1.1 V at full load-enabling use with 5 V input rails supplying 3.3 V logic domains where headroom is limited.

Key Specifications

Pinout & Package

LD1117DT33 is supplied in TO-252 (DPAK) package with exposed thermal pad connected to V_OUT. The TAB is electrically tied to the output pin, enabling direct thermal coupling to PCB copper.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117DT33, LD1117S33TR trades thermal performance for smaller footprint, while TLV1117-33CDCYR sacrifices dropout and accuracy for second-source availability in SO-8-making the DPAK variant optimal for thermally demanding, high-accuracy 3.3 V regulation.

Availability

LD1117DT33 is available at Aetrix Electronics and suitable for industrial PLCs, embedded microcontroller power rails, USB-powered instrumentation, and automotive body control modules requiring stable component supply with long lifecycle support.

Supply support for LD1117DT33 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 standard linear regulator product line, engineered for cost-effective, robust DC/DC conversion in space- and thermal-constrained applications where simplicity and reliability outweigh ultra-low quiescent current requirements.

FAQ

What is the minimum load current required for LD1117DT33 stability?

The LD1117DT33 requires a minimum load current of 2–5 mA to maintain regulation and avoid output voltage drift. This is achieved by placing a 1 kΩ–3.3 kΩ pull-down resistor from VOUT to GND if the connected circuit draws less than 2 mA in all operating states-such as during deep sleep modes of microcontrollers.

Can LD1117DT33 be used with ceramic output capacitors?

Yes-LD1117DT33 is stable with ceramic output capacitors ≥10 µF, including X5R and X7R types. Unlike older LDOs, it does not require ESR-based damping; however, capacitor voltage rating must exceed the maximum expected input voltage (≥16 V recommended for 15 V max input).

How does thermal performance differ between DPAK and TO-220 packages?

DPAK (LD1117DT33) has R_thJA = 100 °C/W, while TO-220 (LD1117PT33) achieves 50 °C/W with heatsink. Without PCB copper, DPAK reaches thermal limit at ~4 W dissipation (e.g., 5 V_IN–3.3 V_OUT × 800 mA = 1.36 W), allowing full-rated current with ≥2 cm² 2-oz copper pour.

Is LD1117DT33 pin-compatible with other 3.3 V LDOs in DPAK?

No-LD1117DT33 uses standard DPAK pinout (VIN–GND–VOUT), but many competing 3.3 V LDOs (e.g., MIC29302, TPS7A47) use different pin assignments. Always verify pin function per datasheet; swapping without layout revision risks reverse-biasing or short-circuit conditions.