STMicroelectronics LF85CDT

Overview

LF85CDT from STMicroelectronics is a 8.5 V fixed-output, very low dropout (LDO) linear voltage regulator in TO-220FP package with logic-controlled shutdown, 500 mA output current capability, ±2% output voltage accuracy at 25°C, and 0.45 V typical dropout voltage at 200 mA. It serves as a local power supply for microcontroller peripherals in battery-powered industrial sensors.

For engineers reviewing the LF85CDT datasheet, LF85CDT pinout, LF85CDT application, or LF85CDT equivalent, key selection criteria include dropout voltage under 500 mA load, quiescent current in ON/OFF modes, thermal resistance (R_thJC = 5°C/W), stability with 2.2 µF ceramic output capacitor, and TTL-compatible enable input behavior across –40 to 125°C junction temperature range.

Technical Context

The LF85CDT implements a PNP pass transistor architecture enabling ultra-low dropout voltage and high PSRR (80 dB typ. at 120 Hz). Its internal current and thermal limiting protect against fault conditions without external components.

It features a dedicated TTL-compatible control input (pin 2) that enables full electronic shutdown with 50 µA max quiescent current, making it suitable for dynamic power gating in multi-rail embedded systems where standby current minimization is critical.

Key Specifications

Pinout & Package

LF85CDT is housed in a TO-220FP (Full Pack) thermally enhanced 5-pin package with isolated tab, optimized for surface-mount assembly and improved heat dissipation over standard TO-220.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL112PU33R and LD3985M85R, the LF85CDT uniquely delivers 8.5 V at 500 mA with integrated enable functionality and TO-220FP thermal robustness-making it the only option among the three capable of sustaining industrial-grade loads while supporting intelligent power sequencing.

Availability

LF85CDT is available at Aetrix Electronics and suitable for industrial sensor nodes, automotive body control modules, programmable logic controller I/O cards, and medical portable monitors requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LF85CDT 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 microcontrollers, power management ICs, sensors, and automotive-grade analog devices since 1987.

The LF00 series was developed specifically for low-noise, low-power industrial and automotive applications demanding high accuracy, wide temperature operation, and reliable shutdown control-addressing gaps in legacy LDO offerings for battery-critical and thermally constrained designs.

FAQ

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

The LF85CDT requires an input voltage ≥8.95 V to maintain regulation at 500 mA, based on its maximum dropout voltage of 0.45 V (typ.) and 0.7 V (max) at that load. At 200 mA, dropout is 0.2–0.35 V, allowing operation down to ~8.7 V input. Input must remain within absolute max rating of 40 V.

Can the LF85CDT be used without the enable pin connected?

Yes - leaving pin 2 (EN) open or tying it to V_IN forces the device into permanent ON state. However, doing so forfeits shutdown capability and increases quiescent current to 500 µA typ. instead of 50 µA. For always-on applications, this is acceptable and electrically safe.

Is a bypass capacitor required on the input pin?

A 0.1 µF ceramic capacitor is recommended between V_IN and GND per the datasheet test circuits. While not strictly mandatory for basic regulation, it improves transient response and reduces high-frequency noise coupling from upstream sources - especially important when fed by switch-mode supplies.

Does the LF85CDT require a minimum load current to maintain regulation?

No - the LF85CDT is stable and maintains regulation from zero load up to 500 mA. Its design does not impose a minimum load requirement, unlike some older LDO architectures. This enables use in intermittent-duty applications such as wake-on-event sensor systems.