STMicroelectronics LF33CV

Overview

LF33CV from STMicroelectronics is a very low-dropout linear voltage regulator delivering a fixed 3.3 V output at up to 500 mA, featuring 0.45 V dropout (typ. 0.35 V at 500 mA), 50 µA quiescent current in OFF mode, and logic-controlled electronic shutdown. It is designed for local regulation in automotive and industrial systems requiring stable low-noise power under wide input (4.3–16 V) and temperature (−40 to +125 °C) ranges.

For engineers reviewing the LF33CV datasheet, LF33CV pinout, LF33CV application, or LF33CV equivalent, this device is evaluated for battery-powered subsystems, ECU power domains with standby control, and noise-sensitive analog rails where minimal dropout and low quiescent current are critical selection criteria.

Technical Context

The LF33CV implements a PNP pass transistor architecture enabling ultra-low dropout and high PSRR (80 dB at 120 Hz). Its internal circuit includes thermal shutdown, current limiting, and TTL-compatible inhibit logic (pin 2 in PPAK/DPAK variants) that fully disables output and reduces IQ to 50 µA.

Stability is achieved with only 2.2 µF output capacitance (ESR 0.1–10 Ω), eliminating need for large ceramic or tantalum capacitors. The device meets AEC-Q100 Grade 1 qualification when ordered in DPAK or PPAK packages, supporting automotive applications across −40 °C to +125 °C junction temperature.

Key Specifications

Pinout & Package

LF33CV is available in TO-220, TO-220FP, DPAK, and PPAK packages. For the 5-pin PPAK and DPAK variants (which include inhibit functionality), the pinout is standardized per Figure 2 of ST's DocID2574 Rev 31: TAB is electrically connected to GND.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LDL1133PU33R, LF33CV delivers 67% more output current and automotive qualification at the cost of larger footprint and higher OFF-mode IQ; versus TPS7B6733QPWPRQ1, it offers lower dropout and IQ but lacks integrated reset and has slightly lower PSRR.

Availability

LF33CV is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC power domains, and battery-powered data loggers requiring stable component supply with long-term lifecycle assurance and AEC-Q100-compliant variants.

Supply support for LF33CV 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 devices.

The LFXX series was developed specifically for automotive and industrial applications demanding robust, low-dropout regulation with logic-controlled shutdown - targeting ECU, telematics, and harsh-environment control systems.

FAQ

What is the minimum input voltage required for LF33CV to maintain regulation at 500 mA?

The minimum input voltage is calculated as V_OUT + V_DROP = 3.3 V + 0.35 V = 3.65 V (typical). Per datasheet Table 11, V_DROP is guaranteed ≤0.7 V at 500 mA and 25 °C, so 4.0 V ensures regulation across temperature and process variation. Input below 4.3 V may cause instability or foldback.

Can LF33CV be used without the inhibit function?

Yes - in TO-220 and TO-220FP 3-pin variants, the inhibit function is absent and the device operates permanently enabled. For 5-pin DPAK/PPAK packages, tying INH to VIN (or >2 V) forces ON mode; leaving it floating is not recommended due to potential oscillation - tie to GND or VIN via resistor per layout guidelines.

Is an input capacitor required for LF33CV stability?

No input capacitor is required for basic stability per ST's test circuit (CI = 0.1 µF is shown for measurement only). However, a 1 µF ceramic capacitor placed close to the IN pin is strongly recommended to suppress high-frequency noise and transient spikes from upstream supplies - especially in automotive environments with load-dump events.

How does thermal performance differ between DPAK and TO-220 packages?

DPAK has R_thJA = 100 °C/W (vs. 50 °C/W for TO-220), meaning it heats significantly faster under identical conditions. At 500 mA and 12 V input, power dissipation is ~4.4 W; TO-220 can sustain this with minimal heatsink, while DPAK requires ≥10 cm² 2-oz copper pour and possibly forced air to stay within 125 °C junction limit.