STMicroelectronics LD49300PT08R

Overview

LD49300PT08R from STMicroelectronics is a 3.0 A, adjustable-output low-dropout linear voltage regulator with dual-supply architecture (VIN = 1.4–5.5 V, VBIAS = 3–6 V), ±1.5% output accuracy at 25 °C, 400 mV max dropout at 3 A, and 10 MHz bandwidth for fast transient response. It powers microprocessor core voltages in PC add-in cards and graphics processors where ultra-low input voltage and tight regulation are critical.

For engineers reviewing the LD49300PT08R datasheet, LD49300PT08R pinout, LD49300PT08R application, or LD49300PT08R equivalent, key selection criteria include dual-rail bias operation, ADJ-pin-based 0.8 V minimum output setting, PPAK thermal performance, and shutdown control via EN pin - all verified in ST's DocID12861 Rev 4.

Technical Context

The LD49300 implements a dual-supply topology: main input (VIN) delivers output current while bias supply (VBIAS) powers internal control circuitry, enabling VIN as low as 1.4 V independent of output voltage. This decoupling reduces effective dropout and improves PSRR (68 dB at 120 Hz).

Its high-bandwidth error amplifier supports 10 MHz closed-loop bandwidth, enabling sub-µs load transient recovery with ≤10 µF ceramic output capacitance. The ADJ pin references a precision 0.8 V bandgap (±0.024 V over –25 to 125 °C), allowing stable 0.8–4.5 V output via external resistor divider.

Key Specifications

Pinout & Package

LD49300PT08R uses the PPAK (Power Package) thermally enhanced 5-pin surface-mount package with exposed copper tab soldered to PCB ground plane for efficient heat dissipation. Package dimensions: 6.0 × 6.4 × 2.4 mm (L × W × H), with 1.27 mm pin pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout, high-current regulator applications.

Compared with TPS7A8300RGRT and ADM7172ACPZ-R7, LD49300PT08R uniquely supports sub-1.4 V VIN operation via VBIAS decoupling, offers full 0.8–4.5 V adjustability, and delivers rated 3 A with 400 mV dropout - making it optimal for ultra-low-voltage, high-transient microprocessor core supplies.

Availability

LD49300PT08R is available at Aetrix Electronics and suitable for graphics processor core supplies, PC add-in card power, and microprocessor core voltage regulation requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LD49300PT08R 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.

LD49300 belongs to ST's high-performance LDO portfolio targeting high-current, low-noise power delivery for advanced digital ICs - specifically engineered for microprocessor, GPU, and FPGA core voltage applications demanding ultra-fast transient response and dual-supply flexibility.

FAQ

What is the minimum required output capacitance for stability?

The LD49300PT08R requires a minimum 1 µF ceramic capacitor (X5R/X7R) placed directly at the VOUT pin for guaranteed stability. While 1 µF suffices for basic operation, ST recommends 10 µF for optimal transient response and to prevent overvoltage stress during short-circuit events when VIN exceeds 4 V. ESR must remain within the stable region defined in Figure 18 of the datasheet.

How should the EN pin be handled if not used in the design?

If the enable function is unused, the EN pin must be permanently tied to VIN (not left floating or pulled to VBIAS). Floating EN causes undefined behavior during power-up and may result in erratic regulator activation or failure to start. Tying to VIN ensures continuous operation and avoids unintended shutdown due to leakage or noise coupling.

Can LD49300PT08R operate with VIN = VBIAS?

Yes - LD49300PT08R supports simultaneous VIN and VBIAS startup (Figure 20), but VBIAS must reach its minimum operating value (≥3 V) before or concurrently with VIN. If VBIAS rises significantly slower than VIN (e.g., >10 ms rise time), overvoltage spikes may occur on VOUT. For robust operation, VBIAS should settle first, especially in systems with fast VIN transients (<100 µs).

What thermal design guidance applies to the PPAK package?

The PPAK package relies on PCB copper area for heatsinking: ST specifies θJA ≤ 100 °C/W with ≥200 mm² of 2-oz copper connected to the exposed GND tab via multiple thermal vias. Without added heatsink, junction temperature must stay ≤125 °C under worst-case PD = (VIN − VOUT) × IOUT + (VBIAS × 5 mA). Thermal derating begins above 85 °C ambient unless copper area exceeds 400 mm².