STMicroelectronics LE33CD-TR

Overview

LE33CD-TR from STMicroelectronics is a very low-dropout linear voltage regulator delivering 3.3 V at up to 100 mA output current, featuring 0.2 V typical dropout voltage, ±2% output voltage accuracy at 25 °C, and TTL-compatible inhibit control (pin 5) in SO-8 package for power-gated local regulation in battery-powered sensor nodes and portable instrumentation.

For engineers reviewing the LE33CD-TR datasheet, LE33CD-TR pinout, LE33CD-TR application, or LE33CD-TR equivalent, this device supports low-noise, low-quiescent-current (50 µA OFF / 0.5 mA ON) operation across –40 to 125 °C, with 80 dB supply voltage rejection at 120 Hz and stability using only a 2.2 µF output capacitor.

Technical Context

The LE33CD-TR implements a precision bandgap reference and error amplifier driving a PNP pass transistor, enabling ultra-low dropout operation even under full 100 mA load. Its inhibit input (INH) accepts TTL-level logic to disable output and reduce quiescent current to 50 µA - critical for standby-mode power budgeting in always-on edge devices.

Thermal protection and current limiting are internally implemented; the SO-8 package integrates pins 2, 3, 6, and 7 to the die attach pad for enhanced thermal dissipation (R_thJA = 55 °C/W), supporting continuous operation at elevated ambient temperatures when PCB copper area is used as heatsink.

Key Specifications

Pinout & Package

LE33CD-TR is supplied in an SO-8 surface-mount package (ECOPACK® compliant), with pins 2, 3, 6, and 7 internally fused to the exposed die attach pad for improved thermal performance. The package footprint matches standard SO-8 dimensions (4.9 × 6.0 mm), enabling drop-in compatibility with legacy L78L-series layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD33CVTR and TLV73333PDQNR, the LE33CD-TR uniquely combines TTL-compatible inhibit control, SO-8 thermal performance, and 100 mA capability in a single industrial-grade package - making it optimal for power-gated embedded systems where pin compatibility with L78L footprints and robustness across temperature extremes are mandatory.

Availability

LE33CD-TR is available at Aetrix Electronics and suitable for industrial sensor nodes, automotive body electronics, portable medical monitors, and smart energy meters requiring stable component supply with long lifecycle assurance and traceable sourcing.

Supply support for LE33CD-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 analog products for industrial, automotive, and consumer markets.

The LEXX series was developed to replace legacy 78Lxx regulators with enhanced efficiency, thermal performance, and integration - specifically targeting space-constrained, battery-sensitive, and high-reliability embedded applications.

FAQ

What is the minimum input voltage required for stable 3.3 V output at 100 mA load?

The LE33CD-TR requires a minimum input voltage of 3.5 V to maintain regulation at 100 mA, based on its 0.2 V typical dropout voltage. At worst-case 0.5 V dropout (over temperature), input must be ≥3.8 V. Input below these thresholds causes output to track input linearly, risking system reset.

Can the INH pin be left unconnected, or must it be pulled to a defined logic level?

The INH pin must not be left floating: while the datasheet states "floating defaults to ON mode", noise coupling can cause unintended toggling. If inhibit functionality is unused, ST recommends grounding INH directly to GND (pin 2/6/8) to ensure stable ON operation and avoid false shutdowns in noisy environments.

Is the SO-8 package thermally enhanced compared to standard SO-8, and how should PCB layout accommodate it?

Yes - pins 2, 3, 6, and 8 are internally fused to the die attach pad, reducing R_thJA to 55 °C/W (vs. ~150 °C/W for standard SO-8). To realize this benefit, the PCB must expose a ≥100 mm² copper pour connected to all four GND pins via multiple thermal vias (≥6 × 0.3 mm) to an internal ground plane.

Does the ±2% output voltage tolerance apply over the full temperature range or only at 25 °C?

The ±2% tolerance is specified at T_J = 25 °C. Over –40 to 125 °C, total output variation is ±3.5% (±2% initial accuracy + ±1.5% tempco drift), as confirmed in Table 6 of the datasheet for LE33C variants. This remains within most MCU and sensor supply specifications.