STMicroelectronics LD1117DTTR

Overview

LD1117DTTR from STMicroelectronics is a fixed-output 3.3 V, 800 mA low-dropout linear voltage regulator in DPAK (TO-252) package, featuring 1.1 V typical dropout at 800 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection. It serves as a post-regulator in power management subsystems for microcontroller-based industrial controllers requiring stable 3.3 V rail under variable load and input conditions.

For engineers reviewing the LD1117DTTR datasheet, LD1117DTTR pinout, LD1117DTTR application, or LD1117DTTR equivalent, key selection criteria include dropout voltage at full load, thermal resistance (R_thJA = 100 °C/W), output tolerance over temperature, minimum required output capacitance (10 µF), and compatibility with standard PCB footprints for DPAK packages.

Technical Context

The LD1117DTTR uses an NPN pass transistor architecture to minimize quiescent current consumption-most of the bias current flows into the load rather than being wasted as ground current. This improves efficiency compared to PNP-based LDOs, especially at light loads.

It integrates internal current limiting and thermal shutdown protection, with guaranteed operation across -40 °C to +125 °C junction temperature. The device requires only a single 10 µF ceramic or tantalum output capacitor for stability and achieves 0.01–0.1 %/W thermal regulation during transient pulses.

Key Specifications

Pinout & Package

DPAK (TO-252) surface-mount package with exposed thermal pad connected internally to V_OUT; optimized for high-power density and thermal performance in 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 TLV1117-33CDR and MCP1703T-3302E/MB, the LD1117DTTR delivers superior thermal capability (R_thJA = 100 °C/W) and higher current headroom at full load, making it optimal for industrial-grade 3.3 V power domains where reliability under sustained 800 mA operation is essential.

Availability

LD1117DTTR is available at Aetrix Electronics and suitable for industrial PLCs, embedded MCU power rails, medical sensor interfaces, and automotive body control modules requiring stable component supply with long-term manufacturability and consistent parametric performance.

Supply support for LD1117DTTR 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The LD1117 series belongs to ST's broad portfolio of linear voltage regulators engineered for cost-sensitive, high-reliability applications demanding robust thermal behavior, tight output tolerance, and simple external component requirements.

FAQ

What is the minimum output capacitance required for stability?

The LD1117DTTR requires a minimum 10 µF output capacitor for guaranteed stability across all operating conditions. Ceramic, tantalum, or aluminum electrolytic types are acceptable; ESR between 0.1 Ω and 10 Ω is supported. Lower values may cause oscillation, especially under light load.

Can LD1117DTTR be used with input voltages below 4.4 V?

No - with a 3.3 V output and 1.1 V typical dropout, the absolute minimum input voltage is 4.4 V at 800 mA load. At lighter loads (e.g., 100 mA), dropout drops to 1.0 V, allowing operation down to 4.3 V, but derating is recommended for thermal and process variation margins.

Is the DPAK thermal pad electrically connected?

Yes - the exposed tab (Pin 2) is internally connected to the V_OUT terminal. It must be soldered to a large copper pour tied to the 3.3 V net for both thermal conduction and electrical integrity. Floating or grounding the tab will cause malfunction or damage.

Does LD1117DTTR support reverse-voltage protection?

No - the device lacks integrated reverse-polarity protection. Applying negative voltage to VIN or GND relative to VOUT can cause destructive latch-up. An external series Schottky diode on the input is required for systems subject to accidental reverse connection or battery reversal.