STMicroelectronics LF33ABPT-TR

Overview

LF33ABPT-TR from STMicroelectronics is a 3.3 V fixed-output, low-dropout linear voltage regulator in PENTAWATT-5 package with logic-controlled shutdown, 500 mA output current capability, 0.35 V dropout at 500 mA, ±1% output voltage accuracy at 25°C, and operation from −40 to 125°C junction temperature. It serves as a local power supply for microcontroller cores, sensor interfaces, and low-noise analog circuitry in portable and automotive systems.

For engineers reviewing the LF33ABPT-TR datasheet, LF33ABPT-TR pinout, LF33ABPT-TR application, or LF33ABPT-TR equivalent, key selection criteria include dropout voltage under load, quiescent current in ON/OFF modes, output voltage tolerance across temperature, stability with 2.2 µF ceramic output capacitor, and TTL-compatible enable control timing behavior.

Technical Context

The LF33ABPT-TR implements a PNP pass transistor architecture enabling ultra-low dropout (0.35 V at 500 mA) and high PSRR (80 dB at 120 Hz). Its internal bandgap reference and error amplifier deliver tight DC regulation (±1% VO at 25°C) and low output noise (50 µV RMS, 10 Hz–100 kHz).

Logic-controlled shutdown (pin 2) accepts TTL-level inputs (VIL ≤ 0.8 V, VIH ≥ 2 V), reducing quiescent current to 50 µA typical in OFF mode while maintaining thermal and current limiting protection. The device requires only a 2.2 µF output capacitor with ESR between 0.1 Ω and 10 Ω for unconditional stability.

Key Specifications

Pinout & Package

The LF33ABPT-TR is housed in a PENTAWATT-5 (vertical, 5-pin) thermally enhanced package with exposed tab for heatsinking. 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 low-dropout linear regulator applications.

Compared with LDL1133PU33R and TPS79933DRVR, the LF33ABPT-TR uniquely balances 500 mA drive, sub-0.4 V dropout, integrated TTL shutdown, and ±1% accuracy - making it optimal for automotive and industrial modules requiring robust local regulation with active power management.

Availability

LF33ABPT-TR is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, portable medical devices, and smart energy metering systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LF33ABPT-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, Switzerland, designing and manufacturing microcontrollers, power management ICs, sensors, and automotive-grade analog products.

The LF00 series was developed specifically for low-power, low-noise, and battery-sensitive applications demanding high accuracy, ultra-low dropout, and logic-controlled power gating - targeting automotive infotainment, industrial automation, and portable instrumentation.

FAQ

What is the minimum input voltage required for 3.3 V output at 500 mA load?

The LF33ABPT-TR requires a minimum input voltage of 3.65 V to maintain regulation at 500 mA, based on its maximum dropout voltage of 0.35 V. At lighter loads (e.g., 200 mA), dropout drops to 0.2 V, allowing operation down to 3.5 V input. Input must remain within absolute maximum rating of 16 V.

Can the SHDN pin be left unconnected, or does it require a pull-up/down resistor?

The SHDN pin has an internal pull-down and may be left floating for default ON operation. When driven by an MCU GPIO, no external resistor is needed - it accepts direct TTL logic levels (0–0.8 V = OFF, 2–16 V = ON). Pull-up resistors are unnecessary and may cause unintended shutdown if voltage falls below 2 V.

Is the BP (bypass) pin mandatory to connect, and what happens if it's left open?

The BP pin is internally connected to the bandgap reference node and is intended to be grounded or left floating per ST's application guidance. Leaving it open does not affect regulation or stability. Connecting it to ground improves noise immunity but is optional; no external capacitor is required at this pin.

How does thermal performance compare between PENTAWATT-5 and DPAK packages for this regulator?

In PENTAWATT-5 (LF33ABPT-TR), R_thJA is 50°C/W and R_thJC is 3°C/W. In DPAK, R_thJA rises to 100°C/W and R_thJC to 8°C/W. Thus, the PENTAWATT-5 delivers significantly better heat dissipation - enabling 500 mA continuous output at higher ambient temperatures without heatsinking, unlike DPAK which requires PCB copper area or heatsink for equivalent performance.