Texas Instruments LP38859T-0.8/NOPB

Overview

LP38859T-0.8/NOPB from Texas Instruments is a 3-A, fast-response, high-accuracy LDO linear regulator with dual-rail operation (VIN and VBIAS), 0.8 V fixed output, 240 mV typical dropout at 3 A, ±1% output accuracy at 25°C, and programmable soft-start via external capacitor. It powers DSP/FPGA core rails and SMPS post-regulation in servers and graphics cards.

For engineers reviewing the LP38859T-0.8/NOPB datasheet, LP38859T-0.8/NOPB pinout, LP38859T-0.8/NOPB application, or LP38859T-0.8/NOPB equivalent, key selection criteria include ultra-low VIN capability enabled by separate VBIAS rail, ceramic-capacitor stability (10 µF min), thermal shutdown (160°C), UVLO hysteresis (150 mV), and N-MOS pass transistor architecture enabling low quiescent current across load range.

Technical Context

The LP38859T-0.8/NOPB uses an N-MOS pass transistor driven by a dedicated VBIAS rail (3–5.5 V), decoupling gate drive from power delivery - enabling stable regulation even when VIN approaches VOUT + VDO (as low as 1.1 V). Its CMOS control circuitry delivers 80 dB PSRR at 120 Hz on VIN and 58 dB at 1 kHz on VBIAS.

Soft-start is implemented via internal 13.5 kΩ resistor (rSS) charging an external CSS capacitor at the SS pin, yielding programmable tSS = CSS × 13.5 kΩ × 5; for 10 nF, tSS = 675 µs. Undervoltage lockout activates below ~2.45 V on VBIAS with 150 mV hysteresis, preventing erratic startup.

Key Specifications

Pinout & Package

LP38859T-0.8/NOPB is housed in a 5-pin TO-220 (NDH) package with exposed tab thermally connected to GND. The tab serves as primary heat sink; mounting to PCB copper pour is required for thermal performance (RθJA = 70.7°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A8300RGRT and LP38798SD-0.8/NOPB, LP38859T-0.8/NOPB uniquely balances ultra-low-VIN capability (via VBIAS), TO-220 thermal robustness, and ceramic-capacitor simplicity - making it optimal for high-power, thermally demanding, dual-rail systems where layout flexibility and proven field reliability are prioritized.

Availability

LP38859T-0.8/NOPB is available at Aetrix Electronics and suitable for server core power, FPGA I/O supply, and graphics card VRM support requiring stable component supply, long-term lifecycle assurance, and traceable sourcing for industrial and computing applications.

Supply support for LP38859T-0.8/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 company designing analog ICs, embedded processors, and power management solutions for industrial, automotive, and communications markets.

LP38859T-0.8/NOPB belongs to TI's high-current LDO family engineered for precision core voltage regulation in computing infrastructure - emphasizing low dropout, fast transient response, and dual-rail flexibility to replace legacy bipolar regulators.

FAQ

What is the minimum input voltage required for LP38859T-0.8/NOPB to regulate 0.8 V output?

The LP38859T-0.8/NOPB requires VIN ≥ VOUT + VDO. With a typical dropout voltage of 240 mV at 3 A, the minimum functional VIN is 1.04 V. However, the datasheet specifies a recommended minimum VIN of 1.1 V to ensure reliable operation across temperature and load. VBIAS must simultaneously be ≥3 V for control circuitry activation.

Can LP38859T-0.8/NOPB operate without an external soft-start capacitor?

Yes, LP38859T-0.8/NOPB can operate with the SS pin left open, as the soft-start function is optional. However, omitting CSS removes inrush current limiting, risking voltage droop on shared input rails or triggering upstream current-limit protection. TI recommends at least 1 nF for minimal soft-start effect, especially in systems with large COUT (>100 µF).

What is the purpose of the separate VBIAS pin on LP38859T-0.8/NOPB, and what happens if it is tied to VIN?

The VBIAS pin on LP38859T-0.8/NOPB supplies gate drive and bias current to the internal N-MOS pass transistor and control circuitry independently of the power path. If tied to VIN, the device loses its ultra-low-VIN capability - VIN must then be ≥3 V to meet VBIAS requirements, negating the key advantage of regulating 0.8 V from 1.1 V. Performance degrades due to increased IGND(BIAS) variation with VIN.

Which ceramic capacitor dielectrics are approved for use with LP38859T-0.8/NOPB output?

LP38859T-0.8/NOPB requires X5R or X7R ceramic capacitors for COUT (minimum 10 µF) to ensure stable operation across temperature. Z5U and Y5F dielectrics are explicitly excluded due to excessive capacitance loss at temperature extremes. Tantalum capacitors may be used in parallel but are not substitutes for the mandatory X5R/X7R ceramic bulk capacitor.

How does thermal performance differ between the TO-220 (LP38859T-0.8/NOPB) and DDPAK/TO-263 (LP38859S-0.8/NOPB) packages?

LP38859T-0.8/NOPB in TO-220 has RθJA = 70.7°C/W (JEDEC High-K board, no heatsink), while LP38859S-0.8/NOPB in DDPAK/TO-263 achieves 43.2°C/W. The TO-220's higher thermal resistance necessitates direct mounting of the tab to a large copper pour or external heatsink for 3-A operation above 50°C ambient. The DDPAK offers superior PCB-level thermal transfer but requires surface-mount assembly.