Texas Instruments LP2951CN

Overview

LP2951CN from Texas Instruments is an 8-pin adjustable micropower low-dropout (LDO) voltage regulator with logic-controlled shutdown, error flag output, and programmable output (1.24 V to 29 V). It delivers up to 100 mA with 75 µA typical quiescent current, 380 mV dropout at full load, and ±0.5% initial output accuracy - ideal for battery-powered instrumentation requiring precise undervoltage detection and power sequencing.

For engineers reviewing the LP2951CN datasheet, LP2951CN pinout, LP2951CN application, or LP2951CN equivalent, key selection criteria include its integrated error comparator threshold (±5% VOUT), shutdown input compatibility (2 V logic high), feedback bias current (20–40 nA), and stability with 1–2.2 µF low-ESR capacitors in space-constrained portable systems.

Technical Context

The LP2951CN integrates a precision 1.235 V bandgap reference, error amplifier with SENSE/FEEDBACK inputs, and a PNP pass transistor enabling ultra-low dropout operation. Its dual-path sensing (SENSE pin for remote feedback, OUT pin for local regulation) supports both fixed and resistor-programmed outputs while maintaining tight line (0.03% typ) and load (0.04% typ) regulation across –40°C to +125°C.

Shutdown control disables the pass element and reduces ground current to ≤10 µA, while the ERROR output asserts low when VOUT drops >5% below nominal - implemented via a dedicated comparator referenced to the internal 1.235 V reference and scaled by external resistor divider gain. VTAP provides access to the internal 1.235 V reference for calibration or monitoring.

Key Specifications

Pinout & Package

LP2951CN is supplied in an 8-pin SOIC (D) package measuring 4.90 mm × 3.91 mm, with exposed pad not present. Pin 4 (GROUND) must be connected to PCB ground plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV70733PDQNR and MCP1826T-3302E/DB, LP2951CN uniquely combines programmable output, integrated error flag, and logic shutdown in a single SOIC-8 package - reducing BOM count and PCB area in systems requiring multi-voltage rails and robust power monitoring.

Availability

LP2951CN is available at Aetrix Electronics and suitable for battery-powered instrumentation, industrial sensor nodes, medical wearables, automotive body electronics, and portable test equipment requiring stable component supply and long-term lifecycle support.

Supply support for LP2951CN 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 specializing in analog and embedded processing technologies, with leadership in power management ICs for industrial, automotive, and portable applications.

The LP2951CN belongs to TI's LP295x-N micropower LDO family, designed specifically for battery-critical systems demanding ultra-low quiescent current, precise voltage regulation, and integrated power supervision functions.

FAQ

What is the minimum input voltage required for LP2951CN to regulate a 3.3 V output?

The LP2951CN requires a minimum input voltage of 3.68 V to maintain 3.3 V output at 100 mA load, based on its 380 mV typical dropout voltage. At light loads (<100 µA), dropout drops to 80 mV, allowing regulation from as low as 3.38 V. Input must remain ≥2.3 V per absolute maximum ratings, but regulation is not guaranteed below (VOUT + dropout) across temperature and load.

How does the ERROR pin on LP2951CN function, and what external components are needed?

The ERROR pin on LP2951CN is an open-collector output that pulls low when the regulated output drops >5% below nominal - e.g., below 3.135 V for a 3.3 V design. No external pull-up is strictly required if interfacing with a microcontroller GPIO with internal pull-up; otherwise, a 10 kΩ resistor to VCC is recommended. The threshold scales with output voltage via the feedback divider ratio.

Can LP2951CN be used as a precision voltage reference independent of its regulation function?

Yes - the VTAP pin provides direct access to the internal 1.235 V bandgap reference with ±1.2% accuracy over temperature, and the FEEDBACK pin draws only 20–40 nA. This allows LP2951CN to serve as a stable reference for external ADCs, DACs, or comparators while the OUT pin remains unconnected or unused, leveraging its low tempco (20 ppm/°C) and high PSRR.

What is the recommended output capacitor for LP2951CN, and why is ESR important?

TI specifies 2.2 µF ceramic capacitor for 3 V and 3.3 V versions, and 1 µF for 5 V versions - all with ESR between 10 mΩ and 6 Ω. Low-ESR ceramics meet this range and ensure stability without added series resistance. Using capacitors outside this ESR window risks oscillation or poor transient response due to phase margin degradation in the control loop.

Does LP2951CN require the SENSE pin to be connected for basic operation?

No - LP2951CN operates correctly with SENSE pin left unconnected or tied to OUT. When SENSE is open, regulation occurs at the OUT pin. Connecting SENSE to the load side of PCB traces enables remote sensing, correcting for voltage drop across board copper and improving load regulation accuracy by up to 10× in high-current or long-trace layouts.