onsemi LP2951CNG

Overview

LP2951CNG from onsemi is a micropower, low-dropout linear voltage regulator in SOIC-8 package delivering 100 mA output with 5.0 V fixed output, ±1% initial tolerance at 25°C, 380 mV dropout at 100 mA, and 75 µA quiescent current. It integrates error flag output, logic-level shutdown input, and adjustable feedback for programmable output from 1.25 V to 29 V - used in battery-powered instrumentation and portable medical devices requiring stable low-power bias.

For engineers reviewing the LP2951CNG datasheet, pinout, applications, or equivalent options, key selection criteria include its 5.0 V fixed/adjustable dual-mode operation, open-collector error output timing behavior, shutdown threshold voltage (2.0–30 V), thermal regulation (0.05–0.20 %/W), and compatibility with 1.0 µF minimum ceramic output capacitance.

Technical Context

The LP2951CNG implements a PNP pass transistor architecture with internal 1.235 V bandgap reference and error amplifier, enabling precise output regulation across −40°C to +125°C ambient. Its error comparator monitors output deviation ≥5% (e.g., 4.75 V for 5.0 V output) and asserts open-collector low signal without external hysteresis circuitry.

Shutdown control operates at TTL/CMOS-compatible levels: logic "0" (≤0.7 V) enables regulation; logic "1" (≥2.0 V) disables output, reducing quiescent current to ≤10 µA. Feedback pin bias current is 15–40 nA, supporting high-impedance resistor programming while maintaining <0.2% typical error contribution.

Key Specifications

Pinout & Package

LP2951CNG is housed in an 8-pin SOIC package (Case 751, 3.9 mm × 4.9 mm × 1.75 mm), with exposed pad thermally connected to Pin 2 (GND). Pin 1 is Output; Pin 2 is GND; Pin 3 is Input; Pin 4 is Feedback; Pin 5 is Error Output; Pin 6 is VO Tap; Pin 7 is Sense; Pin 8 is Shutdown.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP2951CNG, LP2951ACDR2G offers tighter initial tolerance for metrology-grade accuracy, while NCV2951ACDR2G adds automotive qualification without altering electrical performance - both retain full pin and functional compatibility.

Availability

LP2951CNG is available at Aetrix Electronics and suitable for battery-powered instrumentation, microcontroller power management, medical wearable sensor nodes, and automotive body control module auxiliary rails requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for LP2951CNG 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

onsemi is a global semiconductor supplier delivering energy-efficient silicon solutions for automotive, industrial, cloud, medical, and IoT applications.

The LP2951 series belongs to onsemi's precision linear regulator product line, engineered for ultra-low quiescent current and low-dropout operation in space-constrained, battery-sensitive systems where reliability and thermal robustness are critical.

FAQ

What is the maximum input voltage rating for the LP2951CNG?

The LP2951CNG has an absolute maximum input voltage rating of 30 Vdc under continuous operation, with a peak transient rating of 32 Vdc for durations under 300 ms. Exceeding these limits risks permanent damage. The device is commonly operated with inputs from 5.5 V to 23 V in fixed 5.0 V mode, ensuring sufficient headroom above dropout while staying within safe thermal limits.

Does the LP2951CNG require an external capacitor on the feedback pin?

No, the LP2951CNG does not require an external capacitor on the feedback (Pin 4) pin for basic operation. However, when using high-value external resistors (>100 kΩ) to program the output voltage, input capacitance at Pin 4 can introduce instability. In such cases, adding a 100 pF capacitor between Pin 1 (Output) and Pin 4 (Feedback), along with increasing the main output capacitor to ≥3.3 µF, restores loop stability per the datasheet guidance.

Can the LP2951CNG be used in adjustable-output configuration?

Yes, the LP2951CNG supports adjustable output from 1.25 V to 29 V using two external resistors connected to the feedback (Pin 4) and sense (Pin 7) terminals. The output voltage follows VOUT = VREF × (1 + R1/R2) + IFB × R1, where VREF = 1.235 V and IFB = 15–40 nA. For 5.0 V fixed operation, tie Pin 6 (VO Tap) to Pin 7 (Sense) and Pin 1 (Output) to Pin 2 (GND) per Figure 19.

What is the purpose of the VO Tap (Pin 6) on the LP2951CNG?

The VO Tap (Pin 6) provides access to an internal 5.0 V reference derived from the bandgap. When used with Pin 7 (Sense), it configures the LP2951CNG for fixed 5.0 V output without external resistors. Connecting Pin 6 to Pin 7 and leaving Pin 4 (Feedback) unconnected activates the internal divider. This pin is not intended for general-purpose voltage sourcing and must not be loaded beyond 10 µA to avoid regulation error.

How does the error output (Pin 5) behave during startup and brownout?

The error output (Pin 5) of the LP2951CNG is an open-collector comparator that pulls low when VOUT falls >5% below nominal (e.g., <4.75 V for 5.0 V output). During startup, it remains high until VIN exceeds ~1.3 V, then goes low once regulation is established (~5.0 V). During brownout, it asserts low before VOUT collapses fully - providing early warning for MCU reset or data save. An external pull-up resistor (100 kΩ–1 MΩ) to VOUT is required for proper logic-level signaling.