STMicroelectronics LF50CP

Overview

LF50CP from STMicroelectronics is a 5 V fixed-output, very low dropout (LDO) linear regulator in TO-220FP package with logic-controlled shutdown, 500 mA output current capability, 0.4 V typical dropout at 500 mA, ±1% output voltage accuracy (AB grade), and operation over –40°C to +125°C junction temperature. It serves as a local power rail regulator in battery-powered portable instrumentation requiring ultra-low quiescent current and high PSRR.

For engineers reviewing the LF50CP datasheet, LF50CP pinout, LF50CP application, or LF50CP equivalent, key selection criteria include dropout voltage under load, shutdown logic compatibility (TTL), thermal resistance (R_thJC = 5°C/W), stability with 2.2 µF ceramic output capacitor, and supply voltage rejection across 120 Hz–10 kHz.

Technical Context

The LF50CP implements a PNP pass transistor architecture enabling sub-0.5 V dropout at full 500 mA load while maintaining tight output regulation. Its internal bandgap reference and error amplifier deliver ±1% initial accuracy and <±25 mV total load/line regulation over operating conditions.

Shutdown is controlled via TTL-compatible input (pin 2), drawing only 50 µA in OFF mode. The device integrates thermal shutdown and current limiting, and achieves 76 dB PSRR at 120 Hz-critical for noise-sensitive analog front-ends in portable medical sensors and industrial data loggers.

Key Specifications

Pinout & Package

LF50CP is housed in a TO-220FP (Full-Pak) package: 5-pin, vertical mounting, isolated tab, plastic body with metal heat slug. Pin 1 = Input, Pin 2 = Shutdown (TTL-compatible), Pin 3 = Ground, Pin 4 = Output, Pin 5 = Bypass (not used in standard configuration; tied to ground per datasheet Figure 1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL112PU50R and LD3985M50R, LF50CP uniquely combines 500 mA drive, integrated TTL shutdown, TO-220FP thermal performance, and ±1% accuracy-making it optimal for thermally demanding, battery-sensitive applications requiring active power sequencing.

Availability

LF50CP is available at Aetrix Electronics and suitable for portable medical devices, industrial data loggers, automotive body electronics, and smart energy meters requiring stable component supply with long-term manufacturability.

Supply support for LF50CP 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

LF50CP belongs to the LF00 series of very low-dropout linear regulators, engineered specifically for battery-powered and thermally constrained applications where ultra-low IQ, high PSRR, and robust protection are mandatory.

FAQ

What is the minimum input voltage required for LF50CP to maintain regulation at 500 mA?

The minimum input voltage is calculated as VO + Vd = 5.0 V + 0.7 V (max dropout at 500 mA) = 5.7 V. Per Table 19, VI must be ≥6.3 V for full 500 mA load regulation, ensuring margin against line and load transients. Below this, output voltage sags proportionally to dropout increase.

Can LF50CP operate without the bypass (Pin 5) connection?

No. Pin 5 (Bypass) must be connected directly to ground per the official STMicroelectronics datasheet (Figure 1, page 3). Leaving it floating risks instability and increased output noise; tying it to GND stabilizes the internal reference and ensures specified PSRR and accuracy performance.

Is LF50CP compatible with ceramic output capacitors having ESR below 0.1 Ω?

No. The datasheet specifies CO stability requires ESR between 0.1 Ω and 10 Ω. Ceramic capacitors with ultra-low ESR (<0.1 Ω) may cause oscillation. A 2.2 µF X7R ceramic with 0.2–0.5 Ω ESR or a small series resistor (e.g., 0.22 Ω) added to low-ESR ceramics ensures stable operation.

How does thermal performance differ between TO-220FP and standard TO-220 for LF50CP?

TO-220FP has R_thJC = 5°C/W versus 3°C/W for standard TO-220. Though slightly higher, TO-220FP provides electrical isolation of the tab-critical when mounting to grounded heatsinks. Its lower R_thJA (60°C/W vs. 50°C/W) also improves natural convection cooling in enclosed spaces.