STMicroelectronics LDL1117S12R

Overview

LDL1117S12R from STMicroelectronics is a fixed 1.185 V (±2% at 10 mA, ±3% over temperature), 1.2 A low-dropout linear voltage regulator in SOT223 package, featuring 350 mV typical dropout at full load, 87 dB PSRR at 120 Hz, and internal thermal/current/power limiting. It operates from 2.5 V to 18 V input and supports DC-DC post-regulation in motherboard point-of-load (P.O.L.) systems.

For engineers reviewing the LDL1117S12R datasheet, LDL1117S12R pinout, LDL1117S12R application, or LDL1117S12R equivalent, this part is selected for stable low-noise 1.2 V rail generation where high PSRR, tight output accuracy, and robust thermal protection are required in industrial and consumer power management designs.

Technical Context

The LDL1117S12R implements a PMOS pass transistor architecture enabling low dropout and high PSRR across frequency-87 dB at 120 Hz, 80 dB at 1 kHz, and 65 dB at 100 kHz. Its control loop is optimized for stability with ceramic output capacitors ≥4.7 μF and ESR < 100 mΩ.

Protection logic integrates three independent mechanisms: current limit (1.5–2 A), SOA-dependent power limiting, and thermal shutdown at 175 °C with 25 °C hysteresis. The tab is electrically connected to VOUT, requiring careful PCB thermal pad routing.

Key Specifications

Pinout & Package

LDL1117S12R is housed in a thermally enhanced SOT223 package with exposed tab connected to VOUT. The package provides low thermal resistance (15°C/W junction-to-case) and supports >1 A continuous operation with proper PCB copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL1117S12R, the LDL1117S12RA offers identical regulation performance with enhanced environmental compliance, while LDL1117S12R-TR delivers identical functionality in machine-ready packaging-neither alters thermal behavior, PSRR, or dropout characteristics.

Availability

LDL1117S12R is available at Aetrix Electronics and suitable for motherboard P.O.L., industrial sensor nodes, and SMPS secondary regulation requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for LDL1117S12R 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, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The LDL1117 series belongs to ST's high-PSRR LDO portfolio, engineered specifically for noise-sensitive post-regulation in switched-mode power supplies and embedded point-of-load applications.

FAQ

What is the minimum input voltage required for stable 1.185 V output at 1.2 A?

The LDL1117S12R requires VIN ≥ VOUT + VDROP. With 350 mV typical dropout at 1.2 A, minimum input is 1.535 V. However, datasheet specifies 2.5 V minimum operating input voltage due to internal bandgap and bias circuitry requirements-so 2.5 V is the absolute lower limit for guaranteed regulation.

Can LDL1117S12R be used without an input capacitor?

No. The datasheet mandates a minimum 1 μF ceramic input capacitor placed adjacent to the VIN pin. Omitting it risks instability, startup failure, and increased susceptibility to input ripple-especially critical when fed from noisy SMPS outputs.

Is the thermal pad (tab) electrically isolated?

No. Per Table 1 and Figure 2 in DS12022 Rev 7, the SOT223 tab is internally connected to VOUT. PCB layout must treat the thermal pad as an extension of the output net-not ground-and avoid solder mask coverage to ensure thermal conduction.

How does the SOA protection affect short-circuit current?

SOA protection dynamically limits short-circuit current based on (VIN – VOUT). At higher dropout voltages, peak current drops below 2 A to prevent excessive power dissipation-e.g., at 5 V dropout, current may be limited to ~1.2 A. This avoids thermal runaway while maintaining safe fault operation.