Texas Instruments LP2951CSD

Overview

LP2951CSD 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 - optimized for battery-powered systems requiring undervoltage detection and power sequencing.

For engineers reviewing the LP2951CSD datasheet, LP2951CSD pinout, LP2951CSD application, or LP2951CSD equivalent, key selection considerations include its integrated error comparator threshold (±5% VOUT), shutdown input compatibility (2 V logic high), feedback bias current (20–40 nA), and stability with low-ESR capacitors (10 mΩ to 6 Ω).

Technical Context

The LP2951CSD integrates a precision 1.235 V bandgap reference, error amplifier, PNP pass transistor, and dual comparators - one monitoring output regulation (ERROR pin), the other enabling logic-controlled shutdown. Its architecture supports both fixed-output configurations (3 V/3.3 V/5 V) and externally programmed outputs via resistor divider on FEEDBACK and SENSE pins.

Unlike the 3-pin LP2950-N, the LP2951CSD implements separate SENSE and FEEDBACK inputs for remote sensing and programmability, plus VTAP for internal resistor tap access. Shutdown mode reduces ground current to ≤10 µA, while ERROR asserts low when VOUT drops >5% below nominal - enabling power-on reset or system fault signaling.

Key Specifications

Pinout & Package

The LP2951CSD is housed in an 8-pin WSON package (4.00 mm × 4.00 mm, exposed thermal pad), optimized for space-constrained PCB layouts and thermal performance (R_θJA = 43.3°C/W with proper vias).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV70733PDBVR and TPS7A2033PDQNR, the LP2951CSD uniquely combines programmable output, integrated error flag, and shutdown control in a single 8-pin WSON - making it the only option among the three capable of replacing multiple discrete functions in battery-critical systems.

Availability

LP2951CSD is available at Aetrix Electronics and suitable for portable medical sensors, industrial IoT edge nodes, smart meter power management, and automotive body control modules requiring stable component supply across long product lifecycles.

Supply support for LP2951CSD 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 delivering analog and embedded processing solutions, with over 50 years of power management innovation and broad distribution infrastructure.

The LP2951CSD belongs to TI's LP295x-N micropower LDO family, designed specifically for battery-powered instrumentation, portable electronics, and systems demanding high accuracy, low dropout, and integrated power supervision.

FAQ

What is the minimum input voltage required for LP2951CSD to regulate a 3.3 V output?

The LP2951CSD requires a minimum input voltage of 2.3 V per datasheet specifications. For stable 3.3 V regulation, VIN must exceed VOUT by at least the dropout voltage - 380 mV at 100 mA load, so VIN ≥ 3.68 V under full load. At light loads, dropout drops to 50–80 mV, allowing operation down to ~3.38 V input. The device remains functional but unregulated below the dropout threshold.

Can LP2951CSD be used as a precision voltage reference independent of regulation?

Yes, the LP2951CSD can serve as a precision 1.235 V reference. Its internal bandgap reference is accessible at the VTAP pin and specified with ±15 mV tolerance and 20 ppm/°C temperature coefficient. When configured with FEEDBACK tied to VTAP and SHUTDOWN held low, the device draws only 75 µA and delivers a stable, low-noise reference - validated in TI's Application Report SNVA222.

How does the ERROR pin behave during startup and dropout events?

The ERROR pin of the LP2951CSD is an open-drain output that remains high-impedance until VOUT reaches ~95% of nominal, then transitions low if VOUT falls >5% below target. During startup, ERROR stays high until regulation is achieved; during dropout, it asserts low within microseconds. Hysteresis of 15 mV prevents chatter near threshold - confirmed in Figure 16 of the LP2951CSD datasheet.

What output capacitor value and ESR range are required for LP2951CSD stability?

The LP2951CSD requires a minimum 2.2 µF ceramic output capacitor with ESR between 10 mΩ and 6 Ω. TI validates stability across this range using X7R/X5R dielectrics; polymer or tantalum caps are acceptable if ESR falls within bounds. Lower ESR (<10 mΩ) risks oscillation unless a small series resistor (≈1 Ω) is added - detailed in Section 9.2.1 of SNVS764Q.

Is LP2951CSD pin-compatible with other LP2951 variants like LP2951CDR?

No, LP2951CSD (WSON-8) is not pin-compatible with LP2951CDR (SOIC-8) despite identical functionality. Pin 1 (OUT) and pin 4 (GND) locations differ between WSON and SOIC footprints, and the WSON exposes a thermal pad (DAP) requiring solder connection to PCB ground - absent in SOIC. Layout redesign is mandatory for substitution.