STMicroelectronics LD1585CD2M33R

Overview

LD1585CD2M33R from STMicroelectronics is a 3.3 V fixed-output, 5 A low-dropout linear voltage regulator in TO-220 package, featuring 1.2 V typical dropout at full load, ±1 % output tolerance at 25 °C, fast transient response, and internal thermal/overcurrent protection. It delivers stable power to high-current digital logic rails in industrial control systems.

For engineers reviewing the LD1585CD2M33R datasheet, LD1585CD2M33R pinout, LD1585CD2M33R application, or LD1585CD2M33R equivalent, key selection criteria include guaranteed 5 A output current, dropout voltage under 1.4 V at 5 A, ±2 % output tolerance over 0–125 °C, TO-220 thermal resistance (R_thJC = 3 °C/W), and adjust-pin-free fixed-voltage operation.

Technical Context

The LD1585CD2M33R implements a PNP-based LDO architecture with on-chip trimmed reference (1.25 V) and error amplifier, enabling fixed 3.3 V output without external resistors. Its fast transient response stems from high-gain error amplification and optimized compensation for ≥10 µF output capacitance.

It operates across 0–125 °C junction temperature with internally limited short-circuit current (5.5–7 A) and thermal shutdown activation at ~150 °C. Input voltage range is up to 30 V DC, with minimum load current of 3–10 mA depending on input conditions.

Key Specifications

Pinout & Package

Supplied in TO-220 package with standard 3-pin configuration: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. The metal tab is electrically connected to Pin 2 (GND) and serves as primary thermal path.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM350KCT/NOPB and LT1529CT-3.3, the LD1585CD2M33R uniquely balances 5 A capability, 1.2 V dropout, and industrial-grade temperature range - making it optimal for space-constrained, high-current 3.3 V rails where both current and thermal robustness are critical.

Availability

LD1585CD2M33R is available at Aetrix Electronics and suitable for industrial PLC I/O modules, FPGA auxiliary power supplies, SCSI-2 interface circuits, and embedded microcontroller systems requiring stable component supply across extended temperature ranges.

Supply support for LD1585CD2M33R 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, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The LD1585C series belongs to ST's high-current linear regulator product line, engineered specifically for industrial and computing applications demanding robust thermal performance, fast transient immunity, and tight DC accuracy without external feedback networks.

FAQ

Is LD1585CD2M33R pin-compatible with other TO-220 LDOs like LM317?

No. LD1585CD2M33R uses Input-Ground-Output pinout (TO-220AB), whereas LM317 uses Adjust-Output-Input (TO-220T). Swapping them without PCB revision causes immediate failure. Always verify pin mapping using ST's mechanical drawing P011C before layout reuse.

What is the minimum input voltage required for stable 3.3 V output at 5 A?

The minimum input voltage is 4.7 V: 3.3 V output + 1.4 V max dropout. Below this, regulation fails and output collapses. At 4.5 V input, output drops to ~3.1 V under full load - confirmed by Figure 11 (dropout vs. current) in the datasheet.

Can LD1585CD2M33R be used without a heatsink?

Only at ≤1.5 W dissipation: e.g., 5 A × (4.7 V − 3.3 V) = 7 W exceeds safe junction rise without heatsinking. With R_thJA = 50 °C/W, ambient 50 °C, junction reaches >400 °C. A heatsink lowering R_thJA to ≤20 °C/W is mandatory for full-load operation.

Does LD1585CD2M33R require an output capacitor, and what type is recommended?

Yes - ≥10 µF output capacitance is mandatory for stability. Tantalum or low-ESR aluminum electrolytic capacitors (ESR ≤ 1 Ω) are specified. Ceramic capacitors alone are insufficient due to ultralow ESR causing phase margin loss; a 1 Ω damping resistor in series may be needed if using ceramics.