STMicroelectronics LDL1117S33R

Overview

LDL1117S33R from STMicroelectronics is a fixed 3.3 V, 1.2 A low-dropout linear voltage regulator in SOT-223 package, featuring 350 mV dropout at full load, 87 dB PSRR at 120 Hz, and ±2% output accuracy at 25°C - deployed for post-regulation in DC-DC converters and point-of-load (PoL) on industrial motherboards.

For engineers reviewing the LDL1117S33R datasheet, LDL1117S33R pinout, LDL1117S33R application, or LDL1117S33R equivalent, key selection criteria include guaranteed 1.2 A output current, thermal shutdown at 175°C, input voltage range of 2.5–18 V, and compatibility with ceramic output capacitors as low as 4.7 μF.

Technical Context

The LDL1117S33R 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-making it suitable for noise-sensitive analog rails downstream of switching regulators. Its internal SOA protection dynamically limits peak current based on dissipated power, not just fixed threshold.

Thermal management integrates dual protection: junction shutdown at 175°C with 25°C hysteresis, plus differential thermal sensing that disables both LDO and channel during rapid thermal gradients. The device requires no external compensation and is stable with standard X5R/X7R ceramic capacitors.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal tab connected internally to VOUT for enhanced heat dissipation; θ_J-C = 15°C/W, θ_J-A = 120°C/W (standard PCB layout).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-33IDCYR and MCP1703T-3302E/MB, the LDL1117S33R delivers superior PSRR and lower dropout at full load-enabling tighter VIN margins and cleaner analog rails-while maintaining robust thermal recovery behavior essential for industrial environments.

Availability

LDL1117S33R is available at Aetrix Electronics and suitable for industrial motor control, SMPS post-regulation, and automotive body control module applications requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LDL1117S33R 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 LDL1117 series belongs to ST's high-PSRR, industrial-grade LDO portfolio-engineered specifically for noise-sensitive post-regulation in switched-mode power supplies and demanding embedded PoL applications.

FAQ

What is the minimum input voltage required for stable 3.3 V output at 1.2 A?

The LDL1117S33R requires VIN ≥ VOUT + VDROP = 3.3 V + 0.35 V = 3.65 V for full 1.2 A output. At lower VIN, output current is reduced per the SOA curve; operation below 2.5 V is prohibited per absolute maximum ratings.

Can the LDL1117S33R be used without an input capacitor?

No. A minimum 1 µF ceramic input capacitor is mandatory for stability and transient response. Omitting it risks oscillation, excessive line-transient overshoot, and potential damage during input voltage surges-per Section 6.2 of DS12022 Rev 7.

Is the thermal pad (tab) electrically isolated or connected?

The SOT-223 thermal tab is internally connected to VOUT, not GND. PCB layout must route the tab to the 3.3 V output net-not ground-to avoid short circuits and ensure proper thermal conduction per Figure 28 and Table 1 of the datasheet.

Does the LDL1117S33R support reverse-voltage protection?

No. The device lacks intrinsic reverse-polarity protection. Applying reverse voltage (e.g., VOUT > VIN) exceeds absolute maximum rating VOUT ≤ VIN + 0.3 V and may cause permanent damage-external diode protection is required in systems prone to back-driving.