Texas Instruments LP3891EMRX-1.2/NOPB

Overview

LP3891EMRX-1.2/NOPB from Texas Instruments is a 1.2 V, 0.8 A ultra-low-dropout linear regulator in SO PowerPAD-8 package, featuring 100 mV typical dropout at full load, 1.5% output voltage accuracy at 25°C, and 60 nA shutdown current. It employs an N-MOS pass transistor with dual-rail operation (VIN + VBIAS) for fast transient response in DSP core and microcontroller power supplies.

For engineers reviewing the LP3891EMRX-1.2/NOPB datasheet, LP3891EMRX-1.2/NOPB pinout, LP3891EMRX-1.2/NOPB application, or LP3891EMRX-1.2/NOPB equivalent, key selection criteria include bias rail dependency (4.5–6 V), thermal design for SO PowerPAD-8 (θJA = 166°C/W), minimum 10 µF tantalum output capacitance, and absence of internal compensation requiring external ESR control.

Technical Context

The LP3891EMRX-1.2/NOPB uses a CMOS-based N-MOS pass transistor architecture with separate VIN and VBIAS inputs-VBIAS drives the gate while VIN supplies load current. This enables operation with input voltages as low as VOUT + VDO (1.3 V min at 0.8 A), unlike bipolar LDOs.

Its control loop requires no internal compensation but mandates strict output capacitor ESR constraints (0.001–0.1 Ω over load range) for stability. Shutdown is active-low on pin 3 (S/D), with 1 µA input current and 20 µs turn-off delay, and under-voltage lockout disables output if VBIAS falls below ~4 V.

Key Specifications

Pinout & Package

LP3891EMRX-1.2/NOPB is housed in an 8-pin SO PowerPAD-8 (DDA) package with exposed thermal pad on underside. The PowerPAD must be soldered to a PCB copper plane for thermal management; vias to inner ground planes are recommended.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL7407LPGEDR and TPS7A2012PDBVR, LP3891EMRX-1.2/NOPB uniquely delivers 0.8 A at 1.2 V with ultra-low dropout via dual-rail architecture-enabling operation from 1.3 V input where alternatives fail, and supporting thermally demanding applications via its PowerPAD-8 thermal interface.

Availability

LP3891EMRX-1.2/NOPB is available at Aetrix Electronics and suitable for server I/O supplies, DSP core power, microcontroller core regulation, and SMPS post-regulation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LP3891EMRX-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 ICs, with decades of expertise in high-reliability linear regulators and power solutions.

The LP3891 series was designed specifically for high-current, fast-transient applications in computing and communications infrastructure-emphasizing ultra-low dropout, dual-rail flexibility, and robust thermal performance in surface-mount packages.

FAQ

What is the minimum input voltage required for LP3891EMRX-1.2/NOPB to regulate 1.2 V output?

The LP3891EMRX-1.2/NOPB requires VIN ≥ VOUT + VDO, where typical dropout is 115 mV at 0.8 A. Thus, minimum VIN is 1.315 V under full load. At lighter loads, dropout decreases-e.g., 30 mV at 10 mA-allowing VIN as low as 1.23 V. Note that VBIAS must also be present (4.5–6 V) for proper gate drive.

Can ceramic capacitors be used for the output of LP3891EMRX-1.2/NOPB?

No-ceramic capacitors alone are unsuitable for the output of LP3891EMRX-1.2/NOPB due to their extremely low ESR (<10 mΩ), which falls outside the stable region (0.001–0.1 Ω). Tantalum is recommended; aluminum electrolytics may be used only above 10°C. Ceramic capacitance can total ≤15% of the main tantalum value if added for high-frequency filtering.

Does LP3891EMRX-1.2/NOPB require an external bias supply, and what happens if it's missing?

Yes-LP3891EMRX-1.2/NOPB requires a 4.5–6 V VBIAS supply on Pin 4 to drive the N-MOS gate. If VBIAS is absent or drops below ~4 V, the internal UVLO circuit disables the output regardless of VIN or S/D state. No regulation occurs without VBIAS, even if VIN is within spec.

How is thermal performance managed in the SO PowerPAD-8 package of LP3891EMRX-1.2/NOPB?

Thermal performance relies entirely on soldering the exposed PowerPAD (Pin 1, 5, 7, and thermal slug) to a PCB copper plane. With no heatsink, θJA is 166°C/W. Adding thermal vias to inner ground planes and ≥1.5 in² copper area reduces effective θJA. Junction temperature must stay ≤125°C-calculate PD = (VIN−1.2)V × IOUT + (VIN × 3 mA) + (VBIAS × 1 mA) to verify margin.

Is LP3891EMRX-1.2/NOPB pin-compatible with other LP3891 variants like LP3891ESX-1.2/NOPB?

No-LP3891EMRX-1.2/NOPB (SO PowerPAD-8, 8-pin) is not pin-compatible with LP3891ESX-1.2/NOPB (DDPAK/TO-263, 5-pin). Pin count, pin functions, and package footprint differ fundamentally. The SO PowerPAD-8 has dedicated GND pins (1,5,7), NC (8), and VBIAS (4); the DDPAK variant consolidates grounds and omits VBIAS and NC pins.