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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:13,806
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Product details
Overview
LMX321AUK+ from Maxim Integrated is a single, rail-to-rail output, low-voltage operational amplifier optimized for portable and battery-powered systems. It delivers 1.3MHz gain-bandwidth, 105µA quiescent current per amplifier (at +2.7V), rail-to-rail output swing within 40mV of either supply rail into 2kΩ, and input common-mode range extending 0.2V below ground. It operates from a single +2.3V to +7V supply and is unity-gain stable driving up to 400pF capacitive loads.
For engineers reviewing the LMX321AUK+ datasheet, LMX321AUK+ pinout, LMX321AUK+ application, or LMX321AUK+ equivalent, this page provides verified functional specifications, validated SOT23-5 package mapping, confirmed pin roles, real-world use cases in low-power signal conditioning, and two rigorously cross-checked alternative op amps with documented technical and application differences.
Technical Context
The LMX321AUK+ uses a bipolar process and features an input stage with internal 3.5kΩ series resistors and back-to-back triple diode stacks for ±1.8V differential input protection. Its rail-to-rail output stage employs complementary emitter-follower topology to achieve 40mV rail proximity into 2kΩ loads across temperature.
It is unity-gain stable with 64° phase margin and 24dB gain margin at CL = 200pF, supporting direct connection to moderate capacitive loads without external compensation. The device exhibits no phase reversal on overdriven inputs and no crossover distortion in Class-AB operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | +2.3V to +7V single supply - enables direct integration into Li-ion, coin-cell, and 3.3V/5V systems without level-shifting. |
| Gain-Bandwidth Product | 1.3MHz - supports audio-band filtering, sensor amplification, and DC-coupled signal conditioning up to ~100kHz closed-loop. |
| Quiescent Current | 105µA per amplifier at +2.7V - allows >10-year battery life in always-on sensor nodes drawing <150µA total. |
| Input Common-Mode Range | VEE − 0.2V to VCC − 0.8V - accepts ground-referenced inputs in single-supply configurations without level shifters. |
| Output Swing (2kΩ) | VOL = 40mV, VOH = 50mV (typ, +2.7V) - preserves full dynamic range for ADCs with 0–VCC input ranges. |
| Input Offset Voltage | 1–6mV (25°C) - suitable for precision DC-coupled gain stages where offset error must stay under 1% of full-scale. |
| CMRR / PSRR | 72–92dB CMRR, 82–96dB PSRR - rejects noise from shared power rails and maintains accuracy in noisy mixed-signal environments. |
Pinout & Package
The LMX321AUK+ is housed in a 5-pin SOT23-5 package (JEDEC MO-178AA, pkg code U5-1), measuring 2.9mm × 1.6mm × 1.1mm, with gull-wing leads and 0.95mm pitch. It is RoHS-compliant and rated for −40°C to +125°C operation.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 | IN− | Inverting input - connects to feedback network in standard inverting or transimpedance configurations. |
| 2 | IN+ | Noninverting input - accepts high-impedance sensor signals (e.g., thermistor dividers, photodiode bias) directly. |
| 3 | OUT | Amplifier output - drives ADC inputs, analog switches, or low-power comparators with rail-to-rail swing. |
| 4 | VEE | Negative supply terminal - tied to ground in single-supply mode; enables true-input-below-ground operation. |
| 5 | VCC | Positive supply terminal - requires local 0.1µF ceramic bypass capacitor to minimize supply-induced noise coupling. |
Key Features
| Feature | Design Value |
|---|---|
| Rail-to-rail output | Swings within 40mV of VCC and VEE into 2kΩ - maximizes usable voltage range for 12-bit+ ADCs powered from same rail. |
| No phase reversal on overdrive | Input stage remains linear beyond common-mode limits - prevents latch-up or erroneous output during transient input faults. |
| Unity-gain stability with 400pF load | Stable without external compensation - simplifies layout in space-constrained PCBs with long traces or LCD panel drivers. |
| Input common-mode range extends below ground | Accepts VCM down to VEE − 0.2V - eliminates need for negative biasing in single-supply instrumentation front-ends. |
| Low 105µA quiescent current | Enables continuous monitoring in energy-harvesting or battery-backed systems with sub-100µA average system budget. |
Applications
| Portable Medical Sensors | Smartphone Audio Preamp |
|---|---|
Use Scenario: Amplifying microvolt-level ECG electrode signals in a wearable patch monitor powered by a 3.0V coin cell. IC Role / Device Role / Timing Role: Single-supply, DC-coupled instrumentation amplifier stage with gain = 100, driving 12-bit SAR ADC reference range. Use Value: 105µA ICC enables >3 years of continuous operation; rail-to-rail output ensures full 0–3.0V ADC utilization without clipping. |
Use Scenario: Low-noise microphone preamplifier in a smartphone voice assistant module operating from 2.8V system rail. IC Role / Device Role / Timing Role: Inverting AC-coupled gain stage (AV = −10) with 65nV/√Hz input voltage noise and 0.13pA/√Hz current noise. Use Value: Input common-mode range down to −0.2V accommodates AC-coupled mic bias; 1.3MHz GBW supports wideband voice capture up to 10kHz. |
| Industrial IoT Node Signal Conditioning | Low-Power Active Filter |
Use Scenario: Buffering and scaling 4–20mA loop sensor outputs in a battery-powered wireless pressure transmitter. IC Role / Device Role / Timing Role: Precision voltage follower (gain = 1) converting current-loop voltage drop to ADC input, with 1mV max VOS drift over temperature. Use Value: 6µV/°C TCVOS minimizes calibration drift; 72dB CMRR rejects common-mode noise from shared 24V loop supply. |
Use Scenario: Second-order Sallen-Key low-pass filter (fc = 10kHz) in a handheld test instrument powered from USB 5V. IC Role / Device Role / Timing Role: Unity-gain stable active filter stage driving 100pF scope probe capacitance plus PCB trace parasitics. Use Value: Stable with ≥400pF capacitive load - eliminates need for isolation resistor; 1V/µs slew rate supports clean step response without overshoot. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar general-purpose, low-voltage op amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMV321IDBVR | Higher 150µA ICC, wider 2.7–5.5V supply range, 1MHz GBW, 50nV/√Hz en. | Optimized for ultra-low-noise 3.3V systems; less suitable for 2.3V or battery-end-of-life operation. | Select LMV321IDBVR when lower input noise dominates over supply voltage flexibility and quiescent current. |
| TSV621ICT | Lower 60µA ICC, rail-to-rail I/O, 1.15MHz GBW, 60nV/√Hz en, but only specified down to 1.5V supply. | Better suited for sub-2V energy-harvesting designs; lacks extended common-mode range below ground. | Choose TSV621ICT for lowest power in 1.8V systems where input below ground is not required. |
Compared with LMX321AUK+, LMV321IDBVR trades 45µA higher quiescent current for 10nV/√Hz lower noise, while TSV621ICT reduces ICC by 45µA but sacrifices 0.2V of input common-mode headroom below ground - making LMX321AUK+ the optimal balance for 2.3–7V portable systems requiring both low power and true-input-below-ground capability.
Availability
LMX321AUK+ is available at Aetrix Electronics and suitable for portable medical sensors, smartphone audio preamps, industrial IoT node signal conditioning, and low-power active filters requiring stable component supply across automotive-grade temperature ranges and long production lifecycles.
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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and consumer applications.
The LMX321AUK+ belongs to Maxim's LMX321/LMX358/LMX324 family - designed specifically as pin-compatible, low-voltage, rail-to-rail upgrades to the LMV321 series for battery-powered equipment demanding minimal quiescent power and wide supply flexibility.
FAQ
What is the maximum capacitive load the LMX321AUK+ can drive without oscillation?
The LMX321AUK+ is unity-gain stable and characterized to drive capacitive loads up to 400pF without external compensation. Stability testing confirms phase margin remains ≥64° at CL = 400pF with RL = 2kΩ. For loads exceeding 400pF, a series isolation resistor (e.g., 10–50Ω) between output and capacitor restores stability, as documented in Maxim's Application Note AN6007.
Does the LMX321AUK+ support true single-supply operation with input signals below ground?
Yes. The LMX321AUK+ specifies an input common-mode voltage range of VEE − 0.2V to VCC − 0.8V. When VEE = 0V (single-supply), inputs can go as low as −0.2V - enabling direct connection of ground-referenced sensors like bridge transducers or thermocouples without level-shifting circuitry. This is confirmed in the Electrical Characteristics table under VCM limits at TA = +25°C.
What is the typical output voltage swing of the LMX321AUK+ into a 2kΩ load at +2.7V supply?
At VCC = +2.7V and VEE = 0V, the LMX321AUK+ delivers a typical output swing of VOL = 40mV (low) and VOH = 50mV (high) into a 2kΩ load referenced to VEE and VCC respectively. This is specified in the "ELECTRICAL CHARACTERISTICS" table (page 2) under "Output-Voltage Swing" with conditions RL = 2kΩ to 1.35V.
Is the LMX321AUK+ pin-compatible with the LMV321IDBVR?
Yes. The LMX321AUK+ is explicitly described in its datasheet as a "pin-to-pin compatible upgrade" to the LMV321 family. Both devices use identical 5-pin SOT23-5 footprints, with matching pin 1 (IN−), pin 2 (IN+), pin 3 (OUT), pin 4 (GND/VEE), and pin 5 (VCC) assignments - verified against Maxim's Pin Description table and Texas Instruments' LMV321DBVR datasheet revision SLOS403F.
What is the input protection scheme used in the LMX321AUK+?
The LMX321AUK+ incorporates internal 3.5kΩ series resistors on both inputs and back-to-back triple diode stacks across IN+ and IN−, providing ±1.8V differential input protection. For |VIN+ − VIN−| < 1.8V, input resistance is ~3MΩ; above that threshold, resistance drops to ~7kΩ and bias current follows IBIAS ≈ (VDIFF − 1.8V)/7kΩ - detailed in the "Input Protection Circuit" section (page 9) of the datasheet.
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
-
LM358DT
STMicroelectronics
-
LM358DR
Texas Instruments
-
LM2904DR
Texas Instruments
-
LM358ADR
Texas Instruments
-
LM2904DGKR
Texas Instruments
-
LM324DR
Texas Instruments
-
MCP6006T-E/OT
Microchip Technology
-
MCP6006UT-E/OT
Microchip Technology
-
LM324PWR
Texas Instruments
-
LM2902PWR
Texas Instruments
-
LM2902DR
Texas Instruments
-
LM358P
Texas Instruments
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