STMicroelectronics ST730M33R

Overview

ST730M33R from STMicroelectronics is a 300 mA, fixed 3.3 V low-dropout (LDO) linear regulator in SOT23-5L package, designed for post-regulation and battery-powered systems requiring ultra-low quiescent current (5 μA typ.), ±0.5% output accuracy at 25 °C, and operation across -40 °C to +125 °C. It supports input voltages from 2.5 V to 28 V and delivers stable 3.3 V output with dropout as low as 200 mV at 100 mA.

For engineers reviewing the ST730M33R datasheet, ST730M33R pinout, ST730M33R application, or ST730M33R equivalent, key selection criteria include its 5 μA no-load IQ, thermal shutdown and current limit protection, compatibility with 0.47 µF low-ESR ceramic output capacitors, and enable-controlled shutdown with 1 μA standby current.

Technical Context

The ST730M33R implements a bandgap-referenced op-amp control loop with internal bias generator and thermal feedback. Its adjustable version uses an ADJ pin referenced to 1.20 V (±12 mV), but the ST730M33R is factory-trimmed for fixed 3.3 V output - eliminating external resistor networks and reducing BOM count.

Protection logic integrates SOA-based current limiting (450 mA short-circuit current), thermal shutdown at 160 °C with 20 °C hysteresis, and enable-driven power gating. The LDO maintains stability with output capacitors ≥0.47 µF and ESR between 5–500 mΩ, independent of load transients up to 300 mA.

Key Specifications

Pinout & Package

SOT23-5L package: 2.95 mm × 1.60 mm × 1.45 mm body height, thermally enhanced leadframe with exposed pad (not electrically connected), JEDEC-compliant footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6219B332MR-G and AP7361-C33W5-7, the ST730M33R uniquely combines 28 V input tolerance, 5 μA IQ, integrated enable, and thermal hysteresis - making it the only option for robust, long-life 24 V industrial or automotive post-regulation where both ultra-low leakage and fault resilience are mandatory.

Availability

ST730M33R 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 across extended temperature and long-lifecycle deployments.

Supply support for ST730M33R 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 sensing solutions for industrial, automotive, and consumer markets.

The ST730 series belongs to ST's precision low-quiescent-current LDO portfolio, engineered specifically for battery-critical and wide-input industrial applications where reliability across extreme temperatures and minimal standby loss are non-negotiable.

FAQ

What is the minimum output capacitor value required for ST730M33R stability?

The ST730M33R requires a minimum 0.47 µF ceramic capacitor (X5R/X7R dielectric) on the VOUT pin, with ESR between 5 mΩ and 500 mΩ. This value is validated across -40 °C to +125 °C and ensures loop stability under all load conditions up to 300 mA. Larger values improve transient response but do not affect stability margins.

Can ST730M33R be used with a 12 V input to deliver 3.3 V at 300 mA?

Yes - with 12 V input and 3.3 V output, the dropout is 8.7 V, well above the maximum specified 1.2 V dropout at 300 mA. Power dissipation will be (12 V − 3.3 V) × 0.3 A = 2.61 W. Using the RthJA of 190 °C/W, junction temperature rise is ~497 °C - exceeding safe limits. Therefore, derating or PCB thermal enhancement (copper pour, vias) is mandatory for continuous 300 mA operation at 12 V.

Is the NC pin (Pin 4) electrically isolated or should it be grounded?

Pin 4 is Not Connected (NC) - it has no internal bond wire or silicon connection. STMicroelectronics datasheet explicitly states it must be left unconnected. Grounding or routing this pin introduces risk of parasitic coupling or unintended current paths and violates the validated SOT23-5L layout guidelines in DS13036 Rev 5, page 15.

How does the enable pin behave during power-up and brown-out conditions?

The EN pin has CMOS-compatible thresholds: logic high ≥1.2 V, logic low ≤0.35 V. During power-up, the device remains in shutdown until VIN exceeds 2.5 V and EN rises above 1.2 V. Under brown-out (VIN dropping below 2.5 V), the LDO ceases regulation but EN retains its state - no automatic reset or hysteresis is built into the enable path itself.