STMicroelectronics LD1117ADT18TR

Overview

LD1117ADT18TR from STMicroelectronics is a fixed-output 1.8 V low-dropout linear voltage regulator delivering up to 1 A output current with 1.15 V typical dropout at full load, ±2% output voltage tolerance at 25 °C, and 80 dB supply voltage rejection at 120 Hz - used in post-regulation of DC-DC converter outputs for FPGA core supplies.

For engineers reviewing the LD1117ADT18TR datasheet, LD1117ADT18TR pinout, LD1117ADT18TR application, or LD1117ADT18TR equivalent, key selection criteria include dropout voltage at 1 A, thermal resistance (R_thJA = 100 °C/W in DPAK), quiescent current (5 mA typ.), and stability with only 10 µF output capacitance.

Technical Context

The LD1117ADT18TR employs an NPN pass transistor architecture enabling low dropout while maintaining high PSRR and thermal stability. It integrates internal current limiting and thermal shutdown, with operation validated across 0 °C to 125 °C junction temperature range.

Designed for fixed 1.8 V output, it requires no external feedback components and achieves 0.5% temperature coefficient and 0.3% long-term stability over 1000 hours at 125 °C - critical for power rails in industrial microcontroller and sensor interface circuits.

Key Specifications

Pinout & Package

LD1117ADT18TR is housed in the DPAK (TO-252) surface-mount package with exposed thermal pad connected to VOUT. The package provides R_thJA = 100 °C/W and R_thJC = 8 °C/W, enabling 1 A operation with minimal heatsinking on standard 2-layer PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-18CDR and MCP1703T-1802E/MB, the LD1117ADT18TR uniquely balances 1 A capability, 1.15 V dropout, and 80 dB PSRR in a thermally efficient DPAK package - making it optimal for industrial and embedded systems demanding both current and noise performance.

Availability

LD1117ADT18TR is available at Aetrix Electronics and suitable for industrial PLCs, FPGA power management, medical sensor modules, and automotive body control units requiring stable component supply with full production lifecycle support.

Supply support for LD1117ADT18TR 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The LD1117A series was developed to provide robust, low-cost LDO regulation for space-constrained embedded systems - emphasizing thermal efficiency, minimal external components, and wide-input compatibility in industrial and computing applications.

FAQ

What is the minimum input voltage required for LD1117ADT18TR to maintain regulation at 1 A?

The minimum input voltage is calculated as V_OUT + V_DROP = 1.8 V + 1.30 V (max dropout @ 1 A) = 3.10 V. In practice, 3.3 V input is recommended to accommodate line and load transients while maintaining regulation margin across temperature and process variation.

Can LD1117ADT18TR be used with ceramic output capacitors?

Yes - the device is stable with 10 µF ceramic capacitors having ESR ≥ 10 mΩ. Unlike older LDOs, it does not require minimum ESR for stability, simplifying layout and enabling use of compact X5R/X7R MLCCs without series resistors.

How does the DPAK package's thermal performance compare to TO-220 for this part?

In DPAK, R_thJA = 100 °C/W versus 50 °C/W in TO-220. However, DPAK's smaller footprint and surface-mount compatibility enable better PCB copper spreading, often achieving comparable thermal performance in production boards with 2 oz. copper and thermal vias - especially where mechanical height constraints prohibit TO-220.

Is there a risk of reverse current flow when VIN drops below VOUT?

No - the LD1117ADT18TR lacks reverse-current protection, so external diode isolation is required if the input may fall below output (e.g., during hot-swap or backup battery switchover). This behavior is inherent to NPN pass transistor topology and documented in ST's application note AN2811.