STMicroelectronics LD1117S18TR

Overview

LD1117S18TR from STMicroelectronics is a fixed-output 1.8 V low-dropout linear voltage regulator delivering up to 800 mA, featuring 1 V typical dropout at 100 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection at 120 Hz - deployed in power rails for microcontroller cores, FPGA I/O banks, and industrial sensor signal chains.

For engineers reviewing the LD1117S18TR datasheet, LD1117S18TR pinout, LD1117S18TR application, or LD1117S18TR equivalent, key selection criteria include dropout performance under 500 mA load, thermal resistance in SOT-223 package, stability with 10 µF ceramic output capacitor, and compatibility with 3.3 V/5 V input sources in space-constrained PCBs.

Technical Context

The LD1117S18TR uses an NPN pass transistor architecture, enabling high efficiency by routing quiescent current primarily into the load rather than ground - unlike PNP-based regulators. This design reduces no-load power loss and improves light-load regulation accuracy.

Internal trimming achieves ±1 % output voltage tolerance at 25 °C and maintains ≤0.5 % temperature stability across –40 °C to +125 °C operating junction range. On-chip thermal shutdown and current limiting protect against fault conditions without external components.

Key Specifications

Pinout & Package

LD1117S18TR is housed in a surface-mount SOT-223 package with exposed thermal tab electrically connected to VOUT. The package provides optimized thermal performance for high-current LDO operation in compact layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV73318PDBVR and AP2202K-18, the LD1117S18TR offers superior current delivery and integrated protection at the expense of higher quiescent current - making it optimal for industrial and automotive applications demanding robustness and sustained load capacity.

Availability

LD1117S18TR is available at Aetrix Electronics and suitable for industrial automation controllers, automotive body electronics, medical sensor modules, and IoT edge nodes requiring stable component supply with long-term manufacturability.

Supply support for LD1117S18TR 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The LD1117 series belongs to ST's standard linear regulator product line, engineered for cost-effective, reliable voltage regulation in space- and thermally-constrained applications where simplicity and proven robustness outweigh ultra-low-power requirements.

FAQ

What is the minimum input voltage required for LD1117S18TR to maintain regulation at 800 mA?

The LD1117S18TR requires VIN ≥ VO + Vd, where Vd is 1.2 V max at 800 mA per datasheet Table 4. Thus, minimum input is 1.8 V + 1.2 V = 3.0 V. Operation below this causes dropout and unregulated output. Input must also stay within absolute max rating of 15 V.

Can LD1117S18TR be used with a 10 µF X7R ceramic capacitor only, without additional bulk capacitance?

Yes - the datasheet explicitly specifies stability with a single 10 µF X5R/X7R ceramic capacitor on the output. No bulk electrolytic or tantalum capacitor is required. Ensure capacitor ESR is <1 Ω and placed within 3 mm of VOUT and GND pins for optimal transient response.

Does the SOT-223 thermal tab require a dedicated thermal via array to PCB ground?

No - the tab is internally connected to VOUT, not GND. It must be soldered to a dedicated VOUT copper pour with ≥4 thermal vias (0.3 mm diameter) to inner-layer copper planes to dissipate heat. Connecting the tab to ground creates a short circuit and will destroy the device.

Is LD1117S18TR qualified for automotive applications per AEC-Q100?

No - LD1117S18TR is rated for industrial temperature range (–40 °C to +125 °C junction), but it is not AEC-Q100 qualified. For automotive use, ST offers the pin-compatible LD1117AV18 in DPAK package with AEC-Q100 Grade 2 qualification (–40 °C to +105 °C ambient).