STMicroelectronics ST732M33R

Overview

ST732M33R from STMicroelectronics is a 300 mA, fixed 3.3 V low-dropout linear regulator in SOT23-5L package, designed for post-regulation and battery-powered systems requiring ultra-low quiescent current (5 µA typ.), ±2% output voltage accuracy, 2.5–28 V input range, and thermal/current protection. It operates from −40 °C to +125 °C and stabilizes with 0.47 µF ceramic output capacitor.

For engineers reviewing the ST732M33R datasheet, ST732M33R pinout, ST732M33R application, or ST732M33R equivalent, key selection criteria include dropout voltage at 300 mA (max 1.2 V), load regulation (0.0001 %/mA), PSRR at 1 kHz (75 dB), and compatibility with low-ESR capacitors in space-constrained industrial and safety-critical modules.

Technical Context

The ST732M33R implements a bandgap-referenced error amplifier with internal bias generator and overtemperature/overcurrent protection circuitry. Its SOA-based current limit varies with (VIN−VOUT) to constrain power dissipation under overload, and thermal shutdown activates at 160 °C with 20 °C hysteresis.

Stability is achieved using a single-pole compensation architecture compatible with 0.47–∞ µF X5R/X7R ceramic output capacitors (ESR 5–500 mΩ). The device delivers regulated 3.3 V output with static line regulation of 0.05 %/V and load regulation of 0.0001 %/mA across full temperature and load range.

Key Specifications

Pinout & Package

SOT23-5L package: 5-pin surface-mount, 1.45 mm height, 2.95 mm × 1.60 mm footprint, thermal pad not present; JEDEC-compliant, RoHS-compliant ECOPACK2.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6206P332MR and AP2202K-3.3, the ST732M33R uniquely combines ultra-low IQ (5 µA), integrated thermal/current protection, and SOT23-5 pinout - making it the only option qualified for long-life, safety-certified, and thermally constrained applications without external protection circuitry.

Availability

ST732M33R is available at Aetrix Electronics and suitable for electronic meters, smoke detectors, portable medical sensors, and industrial PLC I/O modules requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for ST732M33R 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The ST732 series belongs to ST's high-reliability LDO portfolio targeting ultra-low-power, wide-input-voltage applications in safety-critical and battery-operated equipment - emphasizing longevity, protection integrity, and thermal resilience.

FAQ

What is the minimum output capacitor required for stable operation of ST732M33R?

The ST732M33R requires a minimum 0.47 µF X5R or X7R ceramic capacitor on VOUT with ESR between 5 mΩ and 500 mΩ. This value is validated across −40 °C to +125 °C and ensures phase margin >45° without external compensation. Larger values improve transient response but do not affect stability.

Can ST732M33R be used with input voltages below 2.5 V?

No. The absolute minimum operating input voltage is 2.5 V per datasheet Table 5. Below this, regulation fails and output drops nonlinearly; at VIN < 2.5 V, the device may enter undefined state or cease regulation entirely. For sub-2.5 V inputs, consider ST's STLQ015 series.

How does the current limit behavior change with input-to-output differential voltage?

The ST732M33R implements a voltage-dependent current limit: short-circuit current decreases as (VIN−VOUT) increases to cap power dissipation. At VIN = 2.5 V and VOUT = 0 V, ISC ≈ 450 mA; at VIN = 28 V, ISC drops to ~100 mA. This SOA protection prevents thermal runaway during sustained overload.

Is the NC pin (pins 4 and 5) safe to tie to GND or leave floating?

Pins 4 and 5 are Not Connected internally and must remain unconnected on PCB - neither grounded nor routed. Connecting them risks parasitic coupling into sensitive analog nodes or unintended current paths. The recommended footprint isolates these pads with solder mask defined keep-out zones.