STMicroelectronics LD39300DT33-R

Overview

LD39300DT33-R from STMicroelectronics is a 3.3V fixed-output ultra-low-dropout linear regulator in DPAK package, delivering guaranteed 3A output current with 200mV typical dropout at full load and ±1.5% output voltage tolerance at 25°C. It operates from 2.5V to 6V input, features logic-controlled shutdown (INH pin), internal current/thermal limiting, and stable operation with 4.7µF ceramic output capacitor - used in microprocessor core power supplies requiring low-noise, low-quiescent-current regulation.

For engineers reviewing the LD39300DT33-R datasheet, LD39300DT33-R pinout, LD39300DT33-R application, or LD39300DT33-R equivalent, key selection criteria include dropout voltage at 3A, quiescent current in ON/OFF modes, thermal resistance (R_thJA = 100°C/W), stability with ceramic capacitors, and inhibit logic thresholds (V_INH ≤ 0.3V for OFF, ≥ 2V for ON).

Technical Context

The LD39300DT33-R uses BiCMOS process technology to decouple quiescent current from load current - enabling 1.2mA typical I_Q at 3A load and only 1µA max in shutdown. Its error amplifier compares internal 1.22V reference against feedback (not required for fixed versions) to regulate output with fast transient response to line/load steps.

Internal protection includes foldback current limiting (6A short-circuit current), thermal shutdown at 170°C with 10°C hysteresis, and absolute maximum ratings covering VI up to 6.5V, V_INH up to VI+0.3V, and junction temperature range of –40°C to +125°C.

Key Specifications

Pinout & Package

DPAK package (TO-252-3) with exposed thermal pad; thermally enhanced plastic surface-mount housing rated for 100°C/W junction-to-ambient.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TSM1033DTR and MCP1826T-3302E/DB, LD39300DT33-R offers superior dropout (200mV), integrated inhibit control, and lower quiescent current in shutdown - making it optimal for thermally constrained, power-sequenced embedded systems requiring 3A sustained output.

Availability

LD39300DT33-R is available at Aetrix Electronics and suitable for microprocessor core supplies, DSP power rails, industrial PLC I/O modules, and automotive body control units requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LD39300DT33-R 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The LD39300 belongs to ST's high-performance linear regulator product line, engineered specifically for low-voltage, high-current applications demanding ultra-low dropout, fast transient response, and robust thermal/overcurrent protection in space- and power-constrained embedded systems.

FAQ

What is the minimum input voltage required for LD39300DT33-R to maintain regulation at 3A?

The minimum input voltage is VO + V_DROP = 3.3V + 0.2V = 3.5V (typical). At worst-case 400mV dropout (per datasheet max), VI must be ≥3.7V to sustain 3A output. Below this, the device enters dropout and output voltage drops linearly with input.

Can LD39300DT33-R operate without an input capacitor?

No. A minimum 1µF input capacitor is mandatory and must be placed ≤1cm from the VIN pin with low-inductance ground connection. Omitting it risks instability, oscillation, and failure to reject input ripple - especially under fast load transients.

Is the GND pin electrically connected to the DPAK thermal pad?

Yes. The DPAK package's exposed thermal pad is internally connected to the GND terminal. For thermal and electrical integrity, the pad must be soldered to a large copper pour tied directly to the system ground plane - not left floating or insulated.

Does LD39300DT33-R require an external feedback resistor network?

No. As a fixed-output variant (3.3V), the LD39300DT33-R has internal feedback and does not use the ADJ/VSENSE pin. That pin is NC (no connect) in DPAK and must remain unconnected - unlike adjustable versions which require external resistors to set VO.