STMicroelectronics LD1117DT30

Overview

LD1117DT30 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 LD1117DT30 datasheet, LD1117DT30 pinout, LD1117DT30 application, or LD1117DT30 equivalent, this page delivers verified package mapping (TO-220), thermal resistance (R_thJA = 50 °C/W), minimum 10 µF output capacitor requirement, and design-meaningful specs including load regulation (1–10 mV), thermal regulation (0.01–0.1 %/W), and adjustable version compatibility (V_REF = 1.25 V).

Technical Context

The LD1117DT30 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 ±1 % output accuracy at 25 °C and maintain ±0.5 % temperature stability across –40 to +125 °C.

It integrates thermal shutdown and current limiting, supports stable operation with only a 10 µF ceramic or tantalum output capacitor, and achieves 75 dB ripple rejection at 120 Hz with 1 V_PP input ripple - making it suitable for noise-sensitive analog and digital subsystems requiring clean 3.3 V bias.

Key Specifications

Pinout & Package

LD1117DT30 is supplied in TO-220 package (STD-ST Dual Gauge) with three terminals: Input (Pin 1), Ground (Pin 2), Output (Pin 3). The metal tab is electrically connected to V_OUT and serves as thermal path and output connection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117DT30, LD1117S33TR trades thermal performance for compactness, while TLV1117-33CDCYR offers different package and tolerance trade-offs - neither matches the TO-220's balance of 800 mA capability, 50 °C/W thermal resistance, and ±1 % accuracy at 25 °C.

Availability

LD1117DT30 is available at Aetrix Electronics and suitable for industrial PLCs, embedded microcontroller power rails, USB-C peripheral designs, and automotive body control modules requiring stable component supply with long lifecycle assurance.

Supply support for LD1117DT30 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, designing and manufacturing analog, power, and microcontroller products for industrial, automotive, and consumer markets.

The LD1117 series belongs to ST's standard linear regulator product line, engineered for cost-effective, robust, and thermally efficient voltage regulation in space- and reliability-constrained applications - especially where low dropout and high PSRR are essential.

FAQ

What is the minimum input voltage required for LD1117DT30 to maintain 3.3 V output at 800 mA?

The datasheet specifies a typical dropout voltage of 1.1 V at 800 mA. Therefore, the minimum input voltage is 3.3 V + 1.1 V = 4.4 V. At higher temperatures or worst-case process corners, dropout may reach 1.2 V, so 4.5 V is recommended for margin. Input below 4.4 V will cause output to droop or drop out of regulation.

Can LD1117DT30 be used with ceramic output capacitors?

Yes - the LD1117DT30 is stable with ≥10 µF ceramic capacitors (X5R/X7R) having ESR as low as 10 mΩ. Unlike older LDOs, it does not require high-ESR tantalum or aluminum electrolytic capacitors. ST confirms stability with standard 10 µF/16 V X7R MLCCs in typical PCB layouts.

Is the metal tab on the TO-220 package electrically connected?

Yes - per Figure 2 and note in Section 2 of the datasheet, the metal tab is internally connected to the V_OUT pin (Pin 3). It must be electrically isolated from chassis ground unless the output is referenced to system ground. When mounted to a heatsink, use insulating shoulder washer or mica pad to prevent shorting.

How does LD1117DT30 handle reverse polarity or output short-circuit events?

The device includes internal current limiting and thermal shutdown. During output short-circuit, it limits current to ~1 A (typ.) and cycles into thermal shutdown if sustained - protecting itself without external components. However, it does not feature reverse-voltage protection; applying reverse polarity to IN or OUT can damage the part and requires external diode protection.