Texas Instruments LP38858S-1.2/NOPB

Overview

LP38858S-1.2/NOPB from Texas Instruments is a 1.5A fast-response, high-accuracy LDO linear regulator with dual-rail operation (VIN for power path, VBIAS for control circuitry), 1.2V fixed output, 130 mV typical dropout at full load, and soft-start functionality - designed for powering DSP, FPGA, and microcontroller core supplies in server and graphics applications.

For engineers reviewing the LP38858S-1.2/NOPB datasheet, LP38858S-1.2/NOPB pinout, LP38858S-1.2/NOPB application, or LP38858S-1.2/NOPB equivalent, key selection considerations include its dual-supply architecture (VIN/VBIAS), ±1.0% output accuracy at 25°C, stability with 10 µF ceramic output capacitance, thermal shutdown at 160°C, and DDPAK/TO-263–5 package thermal performance.

Technical Context

The LP38858S-1.2/NOPB uses an N-MOS pass transistor driven by a separate VBIAS rail (3.0–5.5V), enabling ultra-low VIN operation down to VOUT + VDO while maintaining fast transient response and low quiescent current. Its CMOS-based control loop achieves stable regulation with minimal external capacitance.

Soft-start is implemented via internal SS-pin resistance (16.0 kΩ typical) and external CSS capacitor, yielding programmable startup time (e.g., 800 µs with 10 nF). Under-voltage lockout (UVLO) activates at ~2.45V on VBIAS with 150 mV hysteresis, ensuring controlled enable/disable sequencing independent of VIN timing.

Key Specifications

Pinout & Package

LP38858S-1.2/NOPB is housed in a thermally enhanced DDPAK/TO-263–5 package (Package Number KTT0005B), with exposed thermal tab soldered to PCB copper plane for low θJC (3°C/W) and effective heat dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL7407LDR and TPS7A8300RGRT, LP38858S-1.2/NOPB uniquely delivers 1.2V/1.5A regulation with dual-rail operation, enabling sub-1.4V input capability and superior transient immunity - making it the only viable choice for high-performance post-regulation in server and graphics platforms.

Availability

LP38858S-1.2/NOPB is available at Aetrix Electronics and suitable for server core supplies, FPGA I/O regulation, and SMPS post-regulator applications requiring stable component supply, long-term lifecycle support, and RoHS-exempt compliance for industrial deployment.

Supply support for LP38858S-1.2/NOPB 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies, with decades of expertise in high-reliability linear regulators and power solutions.

The LP38858 product line was engineered specifically for high-current, low-dropout regulation in computing and communications infrastructure - emphasizing precision, thermal robustness, and compatibility with ceramic capacitors to reduce system size and cost.

FAQ

What is the minimum input voltage required for LP38858S-1.2/NOPB to regulate 1.2V at 1.5A?

The LP38858S-1.2/NOPB requires VIN ≥ VOUT + VDO = 1.2V + 0.13V = 1.33V (typical) at 1.5A load. However, VIN must also be ≤ VBIAS, and VBIAS must be between 3.0V and 5.5V. Therefore, the practical minimum VIN is 1.33V, provided VBIAS is set within its valid range - enabling operation far below conventional LDO limits.

Can LP38858S-1.2/NOPB operate without an external soft-start capacitor?

Yes - the SS pin of LP38858S-1.2/NOPB may be left open if soft-start is not required. However, TI recommends placing a small capacitor (e.g., 100 pF) to minimize noise sensitivity. Without CSS, LP38858S-1.2/NOPB will ramp VOUT at maximum slew rate, potentially causing inrush current exceeding 1.5A during startup.

What is the thermal resistance (θJA) of LP38858S-1.2/NOPB in its DDPAK/TO-263 package?

The LP38858S-1.2/NOPB in DDPAK/TO-263 (KTT0005B) has a θJA of 60°C/W with no added heatsink and still air, and can reach as low as 32°C/W with ≥1 in² of 1-oz copper on the PCB. Its θJC is 3°C/W, confirming highly efficient conduction from die to thermal tab when properly soldered.

Does LP38858S-1.2/NOPB require a specific type of output capacitor?

Yes - LP38858S-1.2/NOPB requires ≥10 µF ceramic output capacitance (X5R or X7R dielectric) placed within 1 cm of the OUT pin and returned directly to the GND pin. Z5U or Y5F ceramics are not recommended due to insufficient capacitance retention over temperature, and aluminum electrolytics are discouraged below 0°C.

How does the VBIAS rail affect the performance of LP38858S-1.2/NOPB?

VBIAS powers the internal reference, error amplifier, and gate driver of LP38858S-1.2/NOPB. It operates independently from VIN, allowing ultra-low VIN operation while maintaining regulation. VBIAS must be 3.0–5.5V; outside this range, UVLO disables regulation. Line regulation on VBIAS is 0.10%/V, so stable biasing is essential for output accuracy.