80mA, Low Dropout Voltage Regulator with Auto Discharge Function in SC70# Technical Datasheet: LMS5214IMG25
## Ultra-Low Noise, High PSRR Linear Voltage Regulator
Manufacturer : NSC (National Semiconductor Corporation)
Document Revision : 1.0
Last Updated : October 2023
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The LMS5214IMG25 is a 250mA, ultra-low noise, high Power Supply Rejection Ratio (PSRR) linear voltage regulator designed for precision analog and RF applications. Its primary function is to provide a clean, stable 2.5V output from a higher input voltage, typically between 2.7V and 5.5V.
* Primary Voltage Regulation : Generating a precise 2.5V rail from common system voltages like 3.3V or 5V.
* Noise-Sensitive Supply Domains : Powering Phase-Locked Loops (PLLs), Voltage-Controlled Oscillators (VCOs), analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and high-fidelity audio codecs where power supply noise directly impacts signal integrity.
* Post-DC/DC Conversion Filtering : Acting as a "clean-up" regulator placed after a switching regulator to attenuate switching noise, leveraging its high PSRR (>60dB at 1kHz).
### 1.2 Industry Applications
* Communications & Networking : RF transceivers, baseband processors, and network interface cards require ultra-low noise supplies for optimal sensitivity and signal clarity.
* Test & Measurement Equipment : High-precision oscilloscopes, spectrum analyzers, and signal generators use such regulators to ensure measurement accuracy by minimizing internal noise sources.
* Medical Imaging & Diagnostics : Ultrasound front-ends, portable monitors, and diagnostic sensors benefit from the stable, noise-free voltage to ensure accurate signal acquisition.
* Professional Audio/Video : Mixing consoles, high-end audio amplifiers, and broadcast equipment utilize these regulators to achieve superior signal-to-noise ratios (SNR).
* Industrial Sensing & Control : Precision sensor interfaces (e.g., for temperature, pressure, or strain gauges) and data acquisition systems (DAQ) require clean power to maintain measurement fidelity.
### 1.3 Practical Advantages and Limitations
Advantages:
* Exceptional Noise Performance : Typical output noise of 30µVrms (10Hz to 100kHz) minimizes phase noise in oscillators and improves SNR in data converters.
* High PSRR : Typically >70dB at 120Hz and >60dB at 1kHz, effectively rejecting ripple from upstream power stages.
* Excellent Line/Load Regulation : Maintains stable output despite variations in input voltage or output current.
* Integrated Protection : Features like thermal shutdown and current limit protect the device and the load under fault conditions.
* Small Form Factor : The MSOP-8 package (IMG25) is suitable for space-constrained PCB designs.
Limitations:
* Fixed Output Voltage (2.5V) : Not adjustable, limiting design flexibility. A different variant must be selected for other voltage requirements.
* Linear Regulator Inefficiency : Power dissipation (P_diss = (V_in - V_out) * I_load) can be significant at higher input-output differentials and load currents, requiring thermal management.
* Limited Input Voltage Range : 2.7V to 5.5V input range may not suit applications with higher or widely varying input supplies without pre-regulation.
* Current Capacity : Maximum 250mA output current is insufficient for high-power loads.
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## 2. Design Considerations
### 2.1 Common Design Pitfalls and Solutions
* Pitfall 1: Inadequate
