STMicroelectronics LF35ABDT-TR

Overview

LF35ABDT-TR from STMicroelectronics is a 3.5 V, ±1% tolerance, very low dropout linear regulator in DPAK package, delivering up to 500 mA output current with 0.4 V typical dropout at 500 mA and 50 µA quiescent current in shutdown mode. It features logic-controlled electronic shutdown (TTL-compatible enable), internal current and thermal limiting, and stable operation with only 2.2 µF output capacitance - optimized for battery-powered portable instrumentation and low-noise sensor power rails.

For engineers reviewing the LF35ABDT-TR datasheet, LF35ABDT-TR pinout, LF35ABDT-TR application, or LF35ABDT-TR equivalent, key selection criteria include dropout voltage at full load, shutdown quiescent current, output voltage accuracy over temperature, stability with low-ESR ceramic capacitors, and thermal performance in DPAK under continuous 500 mA operation.

Technical Context

The LF35ABDT-TR implements a PNP pass transistor architecture enabling ultra-low dropout (0.4 V typ. at 500 mA) and high PSRR (79 dB at 120 Hz). Its 5-pin DPAK configuration includes dedicated IN, OUT, GND, SHUTDOWN (pin 2), and ADJ/SENSE terminals - supporting precise remote sensing and controlled power sequencing in multi-rail systems.

Shutdown is TTL-compatible (V_IL ≤ 0.8 V, V_IH ≥ 2 V), drawing only 50–100 µA in OFF mode while maintaining full thermal and current protection during active and inactive states across –40°C to +125°C junction temperature range.

Key Specifications

Pinout & Package

DPAK (TO-252-5) package: surface-mount, thermally enhanced, 5-terminal outline with exposed thermal pad (connected to GND). Pin 1 = IN, Pin 2 = SHUTDOWN, Pin 3 = GND, Pin 4 = OUT, Pin 5 = ADJ/SENSE.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout regulator applications.

Compared with LDL1135MUTAG and LP38691SD-3.5/NOPB, the LF35ABDT-TR uniquely balances 500 mA capability, 0.4 V dropout, and 50 µA shutdown current in DPAK - making it optimal for thermally demanding, battery-sensitive applications where both current and efficiency matter.

Availability

LF35ABDT-TR is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, battery-powered IoT nodes, and automotive body control units requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LF35ABDT-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 analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The LF00 series was developed specifically for ultra-low-power, low-noise, and battery-critical applications - emphasizing minimal dropout, microamp-level shutdown current, and robustness across extended temperature ranges.

FAQ

What is the minimum input voltage required for the LF35ABDT-TR to maintain 3.5 V output at 500 mA?

The LF35ABDT-TR requires a minimum input voltage of 3.9 V to sustain 3.5 V output at 500 mA, based on its maximum dropout voltage of 0.4 V at that load. At lighter loads (e.g., 200 mA), dropout drops to 0.35 V, allowing operation from as low as 3.85 V input while maintaining regulation.

Can the ADJ/SENSE pin (Pin 5) be left unconnected?

No - Pin 5 (ADJ/SENSE) must be connected directly to the OUT pin (Pin 4) for standard local regulation. Leaving it floating causes unstable output or regulation failure. Remote sensing is only valid when routed to the load's power entry point with dedicated sense traces.

Does the LF35ABDT-TR require an input capacitor?

Yes - a minimum 0.1 µF ceramic capacitor is required between IN and GND, placed as close as possible to Pins 1 and 3. This stabilizes the input impedance and prevents oscillation during transient load steps, especially when sourced from high-impedance or long-trace supplies.

Is the thermal pad on the DPAK package electrically connected?

Yes - the exposed thermal pad on the LF35ABDT-TR's DPAK package is internally connected to Pin 3 (GND). It must be soldered to a GND copper pour on the PCB for both thermal dissipation and electrical integrity; omitting this connection degrades thermal resistance by >30°C/W and risks overheating at full load.