LP2981IM5X-3.0 - 100mA Micropower LDO, 3.0V Fixed | Texas Instruments
MPN: LP2981IM5X-3.0 ✓ ActiveLP2981IM5X-3.0 Overview
What is an LDO (Low-Dropout) linear regulator? An LDO is a type of linear voltage regulator that maintains a stable output voltage even when the input-to-output voltage headroom (dropout) approaches a very small value, often below 200 mV. LDOs sit within the broader voltage regulator family -> power management IC category -> semiconductor hierarchy. Unlike switching regulators, LDOs add no switching noise but dissipate VIN-VOUT x IOUT as heat. They are typically chosen for noise-sensitive analog and RF rails where cleanness matters more than efficiency.
Key features include a 3.0 V fixed output (other voltages available in the LP2981 family), ultra-low quiescent current for standby efficiency, internal current-limit and thermal-shutdown protection, and a stable output with low-ESR ceramic capacitors as small as 1 uF. The new-chip revision (post-NSC) supports an extended 2.5V to 16V input range and ±1% output accuracy across the load/temperature range, while the legacy variant supports VIN to a lower maximum.
Typical applications include powering microcontrollers and MCUs from a 5V or higher rail, USB peripherals, low-power wireless sensor nodes, handhelds, IoT endpoints, and post-DCDC regulation where a quiet, accurate 3.0V rail is needed after a switching pre-regulator. The SOT-23-5 footprint suits space-constrained PCB layouts.
When designing with this device, keep VIN-VOUT dropout margin modest and use a 1 uF or larger ceramic output capacitor with low ESR to ensure regulator stability. Mount the device with adequate copper to share heat; at 100 mA full load with VIN=5V the dissipation is around 200 mW, comfortably inside the SOT-23-5 thermal envelope.
This page synthesizes current distributor pricing, drop-in same-package alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for LP2981IM5X-3.0 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
LP2981IM5X-3.0/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LP2981AIM5X-3.0/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LP2981-33DBVR
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
NCP4586DSQ30T1G
✅ Drop-In📋 Reference alternative (not in catalog)
LP2981IM5X-3.0 Maximum Ratings & Electrical Characteristics
| Output Type | Fixed |
| Nominal Output Voltage | 3.0 V |
| Maximum Output Current | 100 mA |
| Input Voltage Range (New Chip) | 2.5 V to 16 V |
| Output Accuracy | ±1% (new chip, across line/load/temp) |
| Output Voltage Range (Family) | 1.2 V to 5.0 V (new chip) |
| Operating Temperature | -40 C to +125 C |
| Package | SOT-23-5 (DCK) |
| Mounting Type | Surface Mount |
| Output Capacitor | Ceramic, low-ESR, ≥1 uF |
| Protection Features | Current limit, thermal shutdown |
| RoHS Status | Compliant |
| Enable Pin | No (fixed output variant) |
LP2981IM5X-3.0 Pin Configuration
| Pin 1 | VIN — Input supply voltage (2.5V to 16V new chip) |
| Pin 2 | GND — Ground reference |
| Pin 3 | ON/OFF — Shutdown input (logic low disables output) |
| Pin 4 | NC — Not connected (per datasheet) |
| Pin 5 | VOUT — Regulated 3.0V output |
Typical Applications
LP2981IM5X-3.0 is suitable for 6 applications: Microcontroller Power Supply, USB Peripherals and Low-Voltage Logic, Battery-Powered IoT Sensor Nodes, Post-Switching-Regulator Ripple Filter, Handheld and Portable Instruments, Industrial Sensor and Field Wiring.
Microcontroller Power Supply
The LP2981IM5X-3.0 produces a fixed 3.0 V rail ideal for low-power MCUs such as those in the TI MSP430 and NXP Kinetis families. Its micropower quiescent current reduces standby drain in always-on designs, while 100 mA of headroom covers MCU plus support peripherals. The TI LP2981-N datasheet confirms ±1% accuracy and stable operation with a 1 uF ceramic output cap. Designers commonly place the LP2981IM5X-3.0 between a 5 V system rail or Li-ion battery and the MCU's VDD pin to obtain a clean, low-noise supply. Unlike a switching pre-regulator, it adds no ripple to the 3.0 V rail at the cost of VIN-VOUT heat dissipation.
Recommended
USB Peripherals and Low-Voltage Logic
USB peripherals typically require a tightly regulated 3.0 V or 3.3 V rail from a 5 V VBUS source. The LP2981IM5X-3.0 is well matched because its 16 V input tolerance can absorb VBUS transients, and the 100 mA current limit covers most low-power HID and CDC devices. According to the TI LP2981-N datasheet, the part is stable with 1 uF ceramics, simplifying the BOM for cost-sensitive USB dongles. Place the LDO at the VBUS input with input filtering for ESD suppression, and use a 1 uF X5R output cap for transient response.
Recommended
Battery-Powered IoT Sensor Nodes
IoT endpoints powered by Li-ion, LiFePO4, or two-AA cells benefit from the LP2981IM5X-3.0's micropower Iq, which extends standby time significantly compared to larger 100-150 mA LDOs. The 2.5 V minimum input (new chip) keeps the regulator in regulation down to the battery cut-off, ensuring the radio and sensor IC see a stable 3.0 V rail. As the TI LP2981-N datasheet notes, the regulator remains stable with very small ceramic output capacitors, making it ideal for compact sensor modules. Pair with a Bluetooth Low Energy or sub-GHz radio that accepts a 3.0 V supply.
Recommended
Post-Switching-Regulator Ripple Filter
When a switching DC-DC converter provides system power but downstream analog or RF blocks need a quieter rail, the LP2981IM5X-3.0 acts as a post-filter stage. Its high PSRR at low frequencies cleans up the residual ripple from the upstream buck converter, and the fixed 3.0 V output simplifies the analog supply tree. According to the TI LP2981-N datasheet, the small SOT-23-5 footprint allows placement right next to the noise-sensitive IC, minimizing PCB trace-induced noise pickup. Common companions are low-dropout LDOs used after buck converters for mixed-signal SoCs.
Recommended
Handheld and Portable Instruments
Battery-powered test gear, medical handhelds, and barcode scanners often stack a 3.0 V analog rail above a 5V or 12V battery. The LP2981IM5X-3.0 provides a fixed 3.0 V rail with ±1% accuracy, which is critical for ADC reference nodes and sensor excitation. According to the TI LP2981-N datasheet, the thermal-shutdown protection prevents field failures in enclosed handhelds where ambient temperature may rise. Designers often pair the LDO with a low-current instrumentation amplifier on the same 3.0 V rail.
Recommended
Industrial Sensor and Field Wiring
In industrial 24 V sensor loops, a front-end protection block drops the voltage before delivering it to a low-voltage 3.0 V analog or digital section. The LP2981IM5X-3.0 with up to 16 V input tolerance accepts a pre-regulated intermediate rail and produces a fixed 3.0 V for downstream ICs. Per the TI LP2981-N datasheet, the device includes thermal shutdown and current limit, which help the design survive sensor short-circuit faults on the field side. Pair with TVS protection on the field wiring.
Recommended
Recommended Products Summary
Engineering reference data for LP2981IM5X-3.0 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LP2981IM5X-3.0/NOPB | LP2981AIM5X-3.0/NOPB | LP2981-33DBVR | NCP4586DSQ30T1G |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | onsemi |
| Package | SOT-23-5 (DCK) | SOT-23-5 (DCK) | SOT-23-5 (DCK) | SOT-23-5 (DBV) | SOT-23-5 (5-pin) |
| Output Voltage | 3.0 V | 3.0 V | 3.0 V | 3.3 V | 3.0 V |
| Output Current | 100 mA | 100 mA | 100 mA | 100 mA | 150 mA |
| RoHS / Lead-Free | Yes | Yes (NOPB) | Yes (NOPB) | Yes | Yes |
| Lifecycle Status | Active | Active | Active | Active | Active |
Key Differentiators
- Micropower quiescent current for battery applications (vs NCP4586DSQ30T1G)
- Higher input voltage tolerance (new chip) (vs LP2981-33DBVR)
- Wide output voltage options in same family (vs LP2981AIM5X-3.0/NOPB)
Design Notes
Ensure VIN-VOUT dropout margin is respected: at 100 mA full load the LP2981IM5X-3.0 exhibits typical dropout of a few hundred mV (exact value marked [DATA_NEEDED] in the spec list). For a 3.0V output from a 5V rail this gives ample margin, but for low-headroom sources verify the worst-case line/load condition. Adding a small input RC filter (10 ohm + 1 uF) reduces switching noise injection from upstream rails.
Estimated: at VIN=5V, VOUT=3.0V and IOUT=100 mA, dissipation is roughly (5V - 3.0V) * 0.1A = 200 mW. The SOT-23-5 package has a theta_JA around 200 C/W on a standard JEDEC test board, producing an estimated 40 C junction rise above ambient - comfortably inside the 125 C limit. For higher ambient temperatures or hotter rails, increase copper pour around the GND pin to share heat.
Place the 1 uF input and output ceramic capacitors as close as possible to the IC pins to minimize parasitic inductance. Use X5R or X7R dielectric for stability across temperature; avoid Y5V which loses capacitance rapidly with voltage and temperature. The GND pin should be tied to a low-impedance ground plane for best PSRR and thermal performance.
Do not use output capacitors with ESR > 200 mohm - this can cause instability and oscillation on the output. Tie the ON/OFF pin to VIN with a 100 kohm pull-up if shutdown control is not needed (the input is high-impedance and may float). For legacy silicon, verify the maximum VIN rating before connecting to a 12V or 15V rail.
Compliance Information
RoHS and REACH status derived from the TI LP2981 product page and the NOPB suffix designation. LP2981 family is industrial-grade, not AEC-Q100 automotive qualified; for automotive applications consider TPS7A02 or TPS7A4501.
