STMicroelectronics LDL1117S50R

Overview

LDL1117S50R from STMicroelectronics is a fixed 5.0 V, 1.2 A low-dropout linear voltage regulator in SOT-223 package, featuring 350 mV typical dropout at full load, 87 dB PSRR at 120 Hz, and operation from −40 °C to 125 °C. It delivers stable post-regulation for DC-DC converters and motherboard point-of-load (P.O.L.) rails where high ripple rejection and thermal robustness are required.

For engineers reviewing the LDL1117S50R datasheet, LDL1117S50R pinout, LDL1117S50R application, or LDL1117S50R equivalent, this page provides verified electrical specs, thermal behavior, stability requirements, and real-world use cases in SMPS secondary regulation and industrial P.O.L. systems.

Technical Context

The LDL1117S50R employs 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 internal current limit (~2 A) and SOA protection dynamically constrain power dissipation based on VIN–VOUT differential.

Thermal shutdown activates at ~175 °C with 25 °C hysteresis, and differential thermal protection guards against localized hot spots. The regulator requires ≥1 μF input and ≥4.7 μF output ceramic capacitors (X5R/X7R recommended) for guaranteed loop stability across temperature.

Key Specifications

Pinout & Package

SOT-223 package with exposed tab thermally and electrically connected to VOUT; requires copper pour under tab for thermal management and electrical connection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-50 and AP2112K-5.0, the LDL1117S50R uniquely combines 1.2 A delivery, 350 mV dropout, and 87 dB PSRR in SOT-223-making it optimal for thermally demanding, high-rejection P.O.L. roles where both current and noise performance are critical.

Availability

LDL1117S50R is available at Aetrix Electronics and suitable for consumer power rails, industrial sensor nodes, and motherboard point-of-load (P.O.L.) applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LDL1117S50R 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 microcontrollers, power management ICs, analog chips, and MEMS sensors for industrial, automotive, and consumer markets.

The LDL1117 belongs to ST's high-PSRR, thermally robust LDO family targeting DC-DC post-regulation and P.O.L. applications where clean, stable voltage and rugged operation are essential.

FAQ

What is the minimum input voltage required for stable 5.0 V output at 1.2 A?

The LDL1117S50R requires VIN ≥ VOUT + dropout voltage. With 350 mV typical dropout at 1.2 A, minimum VIN is 5.35 V. Absolute minimum operating VIN is 2.6 V per datasheet, but regulation fails below 5.35 V at full load. Always verify margin using worst-case 600 mV dropout spec at temperature extremes.

Can the LDL1117S50R be used without an input capacitor?

No. The datasheet mandates ≥1 μF ceramic input capacitor placed adjacent to VIN and GND pins. Omitting it risks instability, startup failure, and increased susceptibility to input transients. X5R or X7R dielectrics are recommended for stable capacitance across temperature and bias.

How does the SOA protection affect maximum power dissipation?

SOA protection dynamically reduces current limit as VIN–VOUT increases, preventing destructive power levels. At 12 V input and 5 V output (7 V drop), peak current is limited to ~1.1 A-not the full 2 A-ensuring P_D stays within safe limits. Use P_DMAX = (125°C − T_AMB) / θ_J-A as baseline, then derate per SOA curves in Figure 16/17.

Is the exposed tab electrically isolated, and how should it be connected?

No-the exposed tab is internally bonded to VOUT and must be soldered to a dedicated copper pour connected directly to the output net. This serves dual purpose: thermal conduction to PCB and low-impedance VOUT routing. Never float or ground the tab; doing so causes regulation failure and thermal runaway.