STMicroelectronics LDF33DT-TR

Overview

LDF33DT-TR from STMicroelectronics is a 1 A adjustable-output low-dropout linear regulator in DFN6 (3x3) package, operating from 2.6 V to 16 V input and delivering output voltages down to 0.8 V with ±1% precision at 25 °C. It features logic-controlled enable (EN), open-drain Power Good (PG), 500 mV max dropout at 1 A, 200 μA typical quiescent current, and integrated thermal/current protection - designed for powering low-voltage microprocessors and memory in space-constrained portable systems.

For engineers reviewing the LDF33DT-TR datasheet, LDF33DT-TR pinout, LDF33DT-TR application, or LDF33DT-TR equivalent, key selection criteria include its 0.8 V–12 V adjustable output range, fast load transient response, ±1.5% output tolerance over –40 °C to 125 °C, PG threshold accuracy (±0.12×V_ADJ), and DFN6-3x3 thermal resistance (R_thJA = 55 °C/W).

Technical Context

The LDF33DT-TR implements an internal N-channel pass transistor with error amplifier feedback via the ADJ pin, enabling precise output voltage setting using an external resistor divider. Its reference voltage is fixed at 0.8 V (typ), with ±1% tolerance over nominal conditions and ±1.5% across full temperature and load range.

It integrates dual-threshold open-drain PG monitoring (rising edge at 0.92×V_ADJ, falling edge at 0.8×V_ADJ) and EN pin with defined logic thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2 V), supporting reliable power sequencing and shutdown control in multi-rail systems.

Key Specifications

Pinout & Package

Package: DFN6 (3x3 mm, 0.9 mm height), exposed thermal pad connected to GND for enhanced thermal performance (R_thJC = 10 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TSP12345DRVR and NCP1117DT33RKG, the LDF33DT-TR uniquely combines adjustability, integrated PG/EN, ultra-low dropout, and DFN6-3x3 thermal performance - making it the only option among the three capable of meeting tight voltage, size, and sequencing requirements in modern portable and embedded systems.

Availability

LDF33DT-TR is available at Aetrix Electronics and suitable for battery-powered IoT nodes, medical wearable sensor hubs, and industrial PLC I/O modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LDF33DT-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 components for automotive, industrial, and consumer markets.

The LDF series targets high-precision, low-noise point-of-load regulation in space-constrained, thermally demanding applications - emphasizing ultra-low dropout, fast transient response, and integrated power sequencing features.

FAQ

What is the minimum input voltage required for 1.0 V output?

The LDF33DT-TR requires VIN ≥ VOUT + VDROP. With 1.0 V output and maximum dropout of 500 mV at 1 A, minimum VIN is 1.5 V. However, datasheet specifies absolute minimum VIN as 2.6 V for guaranteed operation across all conditions including line/load regulation and temperature extremes - so 2.6 V is the practical lower limit regardless of output voltage.

Can the PG pin drive an LED directly?

No - the PG pin is open-drain with only 6 mA sink capability and no internal pull-up. Driving an LED requires an external pull-up resistor to a supply voltage and a current-limiting resistor in series with the LED. Typical configuration uses 10 kΩ pull-up to 3.3 V and 1 kΩ series resistor to limit LED current to ~2.3 mA, staying within PG's 6 mA rating.

Is the exposed thermal pad electrically connected?

Yes - the exposed pad on the DFN6-3x3 package is internally connected to GND and must be soldered to a PCB copper pour tied to the system ground plane. This connection provides both electrical grounding and primary thermal conduction path; omitting it increases R_thJA by ~20 °C/W and risks thermal shutdown under 1 A load.

How does the ADJ pin function in fixed-output configurations?

The LDF33DT-TR is exclusively an adjustable version - no fixed-output variants exist in this part number. The ADJ pin is mandatory for operation: it connects to the center of a resistor divider between VOUT and GND, establishing feedback for the internal error amplifier. Leaving ADJ unconnected or shorted disables regulation; correct resistor values must be selected per VOUT = 0.8 V × (1 + R1/R2).