STMicroelectronics LF27CDT-TR

Overview

LF27CDT-TR from STMicroelectronics is a 2.7 V fixed-output, very low dropout (LDO) linear regulator in TO-220FP package with logic-controlled shutdown, delivering up to 500 mA output current, 0.2–0.35 V dropout at 200 mA, ±2% output voltage accuracy at 25°C, and operation across –40 to +125°C junction temperature. It serves as a local power rail regulator in battery-powered portable instrumentation requiring ultra-low quiescent current (50 µA in OFF mode) and high PSRR (82 dB at 120 Hz).

For engineers reviewing the LF27CDT-TR datasheet, LF27CDT-TR pinout, LF27CDT-TR application, or LF27CDT-TR equivalent, key selection criteria include dropout voltage under load, shutdown logic compatibility (TTL), thermal resistance (R_thJC = 5°C/W), minimum required output capacitance (2.2 µF), and supply voltage rejection across 120 Hz–10 kHz.

Technical Context

The LF27CDT-TR implements a PNP pass transistor architecture enabling sub-0.4 V dropout at full load, with internal current and thermal limiting for robustness. Its shutdown control (pin 2) accepts TTL-compatible logic levels (V_IL ≤ 0.8 V, V_IH ≥ 2 V) and draws only 10 µA input bias current.

Stability is achieved with a minimal 2.2 µF ceramic output capacitor (ESR 0.1–10 Ω), eliminating need for large electrolytics. PSRR remains ≥77 dB up to 1 kHz and ≥65 dB at 10 kHz, supporting noise-sensitive analog rails like ADC references or RF front-end biasing.

Key Specifications

Pinout & Package

LF27CDT-TR uses the TO-220FP 5-pin package (vertical mounting, isolated tab). 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 or left open per design).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL1127PT50R and TPS7A2027PDQNR, LF27CDT-TR uniquely balances 500 mA drive, TO-220FP thermal performance (5°C/W), integrated shutdown, and wide temperature range - making it optimal for industrial and automotive modules where reliability and headroom matter more than footprint.

Availability

LF27CDT-TR is available at Aetrix Electronics and suitable for battery-powered instrumentation, automotive body electronics, industrial edge nodes, and portable test equipment requiring stable component supply over extended product lifecycles.

Supply support for LF27CDT-TR 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, designing and manufacturing microcontrollers, power management ICs, sensors, and analog components for industrial, automotive, and consumer markets.

The LF00 series was developed specifically for ultra-low-dropout, low-quiescent-current regulation in space- and energy-constrained embedded systems - emphasizing simplicity, thermal resilience, and broad output voltage flexibility.

FAQ

What is the minimum input voltage required for regulation at 500 mA output?

The LF27CDT-TR requires VI ≥ VO + V_d = 2.7 V + 0.7 V = 3.4 V at 500 mA (max dropout 0.7 V per datasheet Table 9). Below 3.4 V, output collapses; typical dropout is 0.4–0.7 V depending on load and temperature. Input must also stay within absolute max rating of –0.5 to 40 V.

Can Pin 5 (Bypass) be left unconnected?

Yes - Pin 5 is unused in standard configurations and may be left floating or tied to ground. STMicroelectronics' application guidance confirms no external connection is required unless implementing advanced noise filtering per AN2482, which is optional and rarely needed for general-purpose 2.7 V regulation.

Is the TO-220FP package thermally isolated?

Yes - the TO-220FP variant features an electrically isolated tab (no internal connection to Pin 3/GND), allowing direct mechanical mounting to a heatsink without insulation hardware. Thermal resistance is R_thJC = 5°C/W, verified per datasheet Table 2.

Does the device require an input capacitor?

Yes - a minimum 0.1 µF ceramic capacitor (X7R, 10 V rated) is required between Pin 1 (Input) and Pin 3 (Ground), placed as close as possible to the device. This stabilizes the input impedance and prevents oscillation during transient load steps, as specified in Figure 2 and Section 4.2 of the datasheet.