STMicroelectronics LD1117S25CTR

Overview

LD1117S25CTR from STMicroelectronics is a fixed-output 2.5 V, 800 mA low-dropout linear voltage regulator in SOT-223 package, featuring 1.1 V typical dropout at 800 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection. It delivers stable power to microcontroller core supplies, sensor analog front-ends, and industrial I/O modules requiring tight regulation under varying load and input conditions.

For engineers reviewing the LD1117S25CTR datasheet, LD1117S25CTR pinout, LD1117S25CTR application, or LD1117S25CTR equivalent, this page provides verified technical context, validated pin functions, real-world application mappings, and confirmed alternative options for 2.5 V LDO replacement in space-constrained PCBs with thermal constraints.

Technical Context

The LD1117S25CTR uses an NPN pass transistor architecture to minimize quiescent current consumption-most of which flows into the load rather than ground-enabling high efficiency at light loads. Its internal bandgap reference and error amplifier maintain regulation across –40 °C to +125 °C junction temperature range.

Stability requires only a single 10 µF ceramic output capacitor; no ESR constraints apply. On-chip thermal shutdown and current limiting protect against fault conditions without external circuitry, and the device operates with input voltages up to 15 V while sustaining full 800 mA output current when dropout margin permits.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal pad connected internally to V_OUT; requires soldering pad to PCB copper pour for thermal performance. Pin 1 = IN, Pin 2 = OUT, Pin 3 = GND, Pin 4 = TAB (V_OUT).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 2.5 V LDO applications.

Compared with TLV1117-25CDR, LD1117S25CTR offers tighter tolerance and lower dropout; compared with MCP1700T-2502E/MB, it delivers >3× output current in the same SOT-223 footprint but with higher quiescent current-making it optimal for medium-power 2.5 V rails where accuracy and headroom are critical.

Availability

LD1117S25CTR is available at Aetrix Electronics and suitable for industrial control panels, medical diagnostic interfaces, and smart metering systems requiring stable component supply with long-term manufacturability assurance.

Supply support for LD1117S25CTR 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 LD1117 series belongs to ST's legacy linear regulator product line, engineered specifically for cost-sensitive, thermally constrained applications demanding high accuracy and robustness without external compensation components.

FAQ

What is the minimum input voltage required for LD1117S25CTR to regulate at full 800 mA?

The minimum input voltage is 3.6 V: 2.5 V output plus 1.1 V typical dropout at 800 mA. At 800 mA load, input must exceed 3.6 V to sustain regulation; below that, output collapses linearly with input. Absolute maximum input is 15 V per datasheet limits.

Can LD1117S25CTR be used with ceramic output capacitors?

Yes-only a 10 µF X5R or X7R ceramic capacitor is required for stability, with no minimum ESR specification. This eliminates need for bulkier, higher-ESR tantalum or aluminum electrolytic capacitors, reducing board area and cost.

How does thermal performance differ between SOT-223 and DPAK packages for LD1117S25CTR?

SOT-223 has R_thJA = 110 °C/W (on 1-in² 2-oz copper); DPAK (TO-252) achieves R_thJA = 100 °C/W under identical layout. DPAK offers slightly better thermal resistance but requires larger footprint; SOT-223 provides superior space efficiency with adequate thermal margin for most 800 mA applications.

Is LD1117S25CTR pin-compatible with other LD1117 fixed-voltage variants?

Yes-all LD1117 fixed versions (1.2 V, 1.8 V, 2.5 V, 3.3 V, 5.0 V) share identical SOT-223 pinout (IN, OUT, GND, TAB). This enables drop-in voltage-scaling upgrades on existing PCBs without layout changes, provided input/output capacitor values remain appropriate for the new output voltage.