STMicroelectronics LD1117DTR

Overview

LD1117DTR from STMicroelectronics is a fixed-output, low-dropout linear voltage regulator delivering up to 800 mA at 3.3 V with 1.1 V typical dropout at 100 mA, ±1 % output tolerance at 25 °C, and 75 dB supply voltage rejection - used in industrial power rails, embedded microcontroller core supplies, and post-regulation stages after switching converters.

For engineers reviewing the LD1117DTR datasheet, LD1117DTR pinout, LD1117DTR application, or LD1117DTR equivalent, this page provides verified pin functions, thermal performance data, stability capacitor requirements, and validated drop-in alternatives for 3.3 V LDO replacement in cost-sensitive, space-constrained PCB designs.

Technical Context

The LD1117DTR 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 error amplifier maintain regulation across input voltages from 4.75 V to 15 V.

Stability is achieved with only a 10 µF minimum output capacitor (tantalum or ceramic), and on-chip trimming ensures ±1 % initial output accuracy at 25 °C. Thermal shutdown and current limiting protect against overload and junction overheating up to 125 °C.

Key Specifications

Pinout & Package

LD1117DTR is supplied in DPAK (TO-252) surface-mount package with exposed thermal pad connected to VOUT. The package enables compact placement and efficient heat transfer to PCB copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-33CDR and MIC29302WU-3.3, LD1117DTR delivers optimal balance of precision (±1 %), thermal efficiency (100 °C/W in DPAK), and low quiescent current (5–10 mA) for mainstream 3.3 V embedded power delivery - making it ideal where accuracy, footprint, and standby power are jointly constrained.

Availability

LD1117DTR is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and consumer IoT devices requiring stable component supply and long-term manufacturability.

Supply support for LD1117DTR 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 specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The LD1117 product line targets cost-effective, robust linear regulation in space- and thermally-constrained applications - emphasizing ease of use, minimal external components, and wide operating temperature support.

FAQ

What is the minimum input voltage required for LD1117DTR to regulate 3.3 V at 800 mA?

The LD1117DTR requires VIN ≥ VO + Vd, where Vd = 1.2 V max at 800 mA and 125 °C. Thus, minimum input is 4.5 V under worst-case thermal conditions. At 25 °C, 4.4 V suffices per typical 1.1 V dropout. Input below 4.4 V causes dropout mode and unregulated output.

Can LD1117DTR be used with ceramic output capacitors?

Yes - the LD1117DTR is stable with ceramic capacitors ≥10 µF and ESR ≥ 0.1 Ω. ST's datasheet confirms compatibility with X5R/X7R types; no series resistor is needed. Avoid ultra-low-ESR ceramics (< 0.05 Ω) unless verified with transient testing.

How does the DPAK thermal pad connection affect reliability?

The DPAK tab is electrically connected to VOUT and serves as primary thermal path. Soldering it to ≥2 cm² of 2 oz copper with ≥4 thermal vias (0.3 mm diameter) reduces junction-to-ambient resistance by ~30 °C/W. Omitting this increases thermal stress and accelerates parametric drift over time.

Is there a recommended input capacitor value and type?

A 1 µF X7R ceramic capacitor placed within 5 mm of VIN and GND pins is recommended to suppress high-frequency noise and prevent oscillation during load transients. Larger values (e.g., 10 µF) improve low-frequency ripple rejection but are not required for stability.