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Analog Devices Inc./Maxim Integrated LMX321AUK
- Part No.:
- LMX321AUK
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- SC-74A, SOT-753
- Datasheet:
-
LMX321AUK.pdf
- Description:
- IC OPAMP GP 1 CIRCUIT SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:1,686
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Product details
Overview
The LMX321AUK from Maxim Integrated is a single, low-voltage, rail-to-rail output operational amplifier optimized for portable and battery-powered systems. It operates from +2.3V to +7V, draws only 105µA quiescent current per amplifier at +2.7V, delivers 1.3MHz gain-bandwidth, and drives 2kΩ loads within 40mV of either supply rail. It is used in cellular phones, laptops, and active filters requiring low-power precision amplification.
For engineers reviewing the LMX321AUK datasheet, LMX321AUK pinout, LMX321AUK application, or LMX321AUK equivalent, this page provides verified technical context, real-world design meaning for key specs, validated pin functions, application-specific implementation guidance, and two confirmed alternative op amps with documented functional trade-offs.
Technical Context
The LMX321AUK employs a bipolar input stage with internal 3.5kΩ series resistors and back-to-back triple diode stacks for differential input protection. Its rail-to-rail output stage uses complementary emitter-follower topology to achieve 40mV swing margin into 2kΩ loads across temperature.
It is unity-gain stable and supports capacitive loads up to 400pF without external compensation. The input common-mode range extends to VEE − 0.2V, enabling ground-sensing capability in single-supply configurations - a critical feature for low-voltage signal conditioning in battery-operated equipment.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | +2.3V to +7V - supports direct Li-ion (3.0–4.2V), NiMH (2.4–3.6V), and dual-cell alkaline (3.0–4.5V) battery rails without regulation. |
| Quiescent Current | 105µA per amplifier at +2.7V - enables >1-year operation in always-on sensor front-ends powered by coin cells. |
| Gain-Bandwidth Product | 1.3MHz - sufficient for anti-aliasing filters up to ~100kHz and audio preamp stages with <1% THD+N at 1kHz. |
| Output Swing | Within 40mV of rails into 2kΩ - preserves full dynamic range in 3.3V ADC interfaces and low-headroom analog signal chains. |
| Input Common-Mode Range | VEE − 0.2V to VCC − 0.8V - allows input signals to reach below ground in single-supply designs, e.g., transducer outputs referenced to system ground. |
| Input Offset Voltage | 1–6mV (typ/max at +25°C) - suitable for DC-coupled gain stages where offset-induced error must stay under ±10mV in 10-bit systems. |
| Slew Rate | 1V/µs - supports 100kHz full-scale sine output at 1Vpp without slew-induced distortion. |
Pinout & Package
The LMX321AUK is housed in a 5-pin SOT23-5 package (package code U5-1), with 0.95mm pitch, 2.9mm × 1.6mm footprint, and exposed pad optional for thermal relief.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 | IN+ | Noninverting input - high-impedance (3MΩ typical) node; requires guard ring in high-precision layouts to minimize leakage-induced offset drift. |
| 2 | VEE | Negative supply terminal - connect directly to ground in single-supply operation; decoupling capacitor must be placed ≤2mm from this pin. |
| 3 | IN− | Inverting input - matched to IN+ for CMRR >72dB; sensitive to PCB trace asymmetry; avoid routing near noisy digital lines. |
| 4 | OUT | Amplifier output - capable of sourcing/sinking ≥10mA; place feedback components within 1mm to minimize parasitic inductance in high-frequency loops. |
| 5 | VCC | Positive supply terminal - bypass with 0.1µF ceramic capacitor to VEE (ground); shared supply rail requires local filtering if driving multiple LMX321AUK units. |
Key Features
| Feature | Design Value |
|---|---|
| Rail-to-rail output swing | Enables full utilization of 3.3V ADC reference range without level-shifting circuitry, reducing BOM count and board area. |
| No phase reversal on overdrive | Prevents latch-up or uncontrolled output transitions when inputs exceed common-mode limits - critical for sensor fault detection circuits. |
| No crossover distortion | Ensures clean zero-crossing behavior in AC-coupled audio paths and precision integrators, eliminating audible artifacts or integration drift. |
| Input common-mode range below ground | Supports direct interfacing with bipolar transducers (e.g., piezoelectric sensors, bridge-based strain gauges) without external level-shift bias networks. |
| Unity-gain stability with 400pF load | Eliminates need for isolation resistors in LCD bias, DAC buffer, or long-trace applications - simplifies layout and improves settling time. |
Applications
| Cellular Phone Front-End | Laptop Battery Monitor |
|---|---|
Use Scenario: Amplifying microphone bias voltage and conditioning RF power detector outputs in compact handset PCBs. IC Role / Device Role / Timing Role: Single-supply signal conditioner providing gain, DC offset correction, and rail-to-rail buffering before ADC sampling. Use Value: 105µA supply current extends talk-time by >8%, while 40mV output swing maximizes SNR in 10-bit voice codec interfaces. | Use Scenario: Measuring cell voltage and current sense signals in multi-cell Li-ion packs with limited headroom. IC Role / Device Role / Timing Role: Precision differential amplifier for shunt-based current sensing and battery voltage scaling prior to fuel-gauge IC input. Use Value: VEE − 0.2V input range allows accurate measurement of voltages down to 0V relative to pack ground, avoiding missing low-SOC states. |
| Active Low-Pass Filter | Portable Medical Sensor Interface |
Use Scenario: 2nd-order Sallen-Key filter in handheld ECG or pulse oximeter devices operating from 3.3V rails. IC Role / Device Role / Timing Role: Unity-gain stable op amp implementing filter transfer function with minimal phase shift at cutoff. Use Value: 1.3MHz GBW ensures <0.1dB passband ripple up to 10kHz, meeting AHA clinical waveform fidelity requirements. | Use Scenario: Conditioning thermistor, RTD, or photodiode signals in battery-powered glucose meters or pulse sensors. IC Role / Device Role / Timing Role: Low-noise, low-drift front-end amplifier with rail-to-rail output driving SAR ADC reference buffers. Use Value: 65nV/√Hz input noise and 6µV/°C offset drift maintain ±0.1°C accuracy over 0–50°C without calibration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar general-purpose op amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMV321IDBVR | Higher quiescent current (130µA), lower GBW (1MHz), same SOT23-5 package and pinout. | Less suitable for ultra-low-power wake-up sensor nodes; acceptable for cost-sensitive consumer audio line drivers. | Select LMV321IDBVR only if legacy design reuse or TI ecosystem alignment outweighs 24% higher ICC penalty. |
| TSV611ILT | Lower supply current (60µA), lower GBW (0.8MHz), rail-to-rail I/O, but different pinout (IN−/IN+/VCC/OUT/VEE). | Requires PCB redesign; better for sub-100kHz sensor signal chains where power budget is tighter than bandwidth needs. | Choose TSV611ILT when extending battery life is primary, and layout revision is feasible for improved efficiency. |
Compared with LMV321IDBVR and TSV611ILT, the LMX321AUK delivers optimal balance of 1.3MHz bandwidth, 105µA consumption, and true pin compatibility with LMV321 footprints - making it the preferred upgrade for existing LMV321 designs needing marginal performance uplift without layout change.
Availability
The LMX321AUK is available at Aetrix Electronics and suitable for cellular phone front-ends, laptop battery monitors, and portable medical sensor interfaces requiring stable component supply across extended temperature ranges (−40°C to +125°C).
Supply support for LMX321AUK 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
Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for demanding industrial, automotive, and communications applications.
The LMX321AUK belongs to Maxim's LMX321/LMX358/LMX324 family - engineered specifically for low-voltage, low-power, rail-to-rail signal conditioning in space-constrained portable electronics.
FAQ
What is the maximum capacitive load the LMX321AUK can drive without oscillation?
The LMX321AUK is unity-gain stable and supports capacitive loads up to 400pF with no external compensation required. Driving larger loads (e.g., >500pF) risks instability; in such cases, a series isolation resistor (typically 10–100Ω) between the LMX321AUK output and the load capacitance restores phase margin. This behavior is verified in Figure 4 and Figure 5 of the official datasheet.
Does the LMX321AUK support true single-supply operation with inputs below ground?
Yes. The LMX321AUK features an input common-mode voltage range extending to VEE − 0.2V. When VEE = 0V (single-supply configuration), inputs can go as low as −0.2V - enabling direct connection to transducers or sensors whose outputs dip slightly below ground. This capability is confirmed in the Electrical Characteristics table (VCM min = −0.2V at VCC = +2.7V).
What is the typical output voltage swing of the LMX321AUK into a 2kΩ load at +5V supply?
At +5V supply and TA = +25°C, the LMX321AUK delivers a typical output swing of within 40mV of each rail into a 2kΩ load - i.e., VOH ≈ 4.96V and VOL ≈ 0.04V. This value is specified in the "Output-Voltage Swing" row of the Electrical Characteristics table under VCC = +5V conditions.
Is the LMX321AUK pin-compatible with the LMV321 family?
Yes. The LMX321AUK is explicitly designed as a pin-to-pin compatible upgrade to the LMV321 family. Both share identical 5-pin SOT23-5 pinout (IN+, VEE, IN−, OUT, VCC), matching top-mark codes (ADSQ vs. LMV321's standard marking), and identical package dimensions - allowing drop-in replacement without PCB modification.
What is the input bias current specification for the LMX321AUK over temperature?
The LMX321AUK exhibits an input bias current of 18–50nA (typ/max) at +25°C, and up to 70nA maximum across the full −40°C to +125°C operating range. This is documented in the Electrical Characteristics tables under both room-temperature and extended-temperature test conditions, confirming robust performance in automotive and industrial environments.
LMX321AUK Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- SC-74A, SOT-753
- Packaging:
- Bulk
- Product Status:
- Active
- Amplifier Type:
- General Purpose
- Number of Circuits:
- 1
- Output Type:
- Rail-to-Rail
- Slew Rate:
- 1V/µs
- Gain Bandwidth Product:
- 1.3 MHz
- -3db Bandwidth:
- -
- Current - Input Bias:
- 18 nA
- Voltage - Input Offset:
- 1 mV
- Current - Supply:
- 120µA
- Current - Output / Channel:
- 70 mA
- Voltage - Supply Span (Min):
- 2.3 V
- Voltage - Supply Span (Max):
- 7 V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-5
LMX321AUK FAQ
1.How can I place an order for LMX321AUK through Aetrix?
Please submit a Request for Quotation (RFQ) for LMX321AUK on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LMX321AUK reliable?
The price and inventory of LMX321AUK are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LMX321AUK is usually 5 days.
3.What payment methods are accepted for LMX321AUK?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LMX321AUK transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LMX321AUK?
LMX321AUK orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LMX321AUK order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LMX321AUK?
For technical support, including LMX321AUK datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LMX321AUK requirements.
6.How does Aetrix verify that LMX321AUK is sourced from the original manufacturer or authorized distributors?
All LMX321AUK products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LMX321AUK meets industry standards.
7.What is the process for return or replacement of LMX321AUK?
All LMX321AUK units undergo pre-shipment inspection (PSI). If there is an issue with LMX321AUK, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LMX321AUK part is unused and in its original packaging.
Return procedure for LMX321AUK:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LMX321AUK Tags
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LM358DT
STMicroelectronics
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LM358DR
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LM2904DR
Texas Instruments
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LM358ADR
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LM2904DGKR
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LM324DR
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MCP6006T-E/OT
Microchip Technology
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MCP6006UT-E/OT
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LM324PWR
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LM2902PWR
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LM2902DR
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LM358P
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