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Texas Instruments LM311MX
- Part No.:
- LM311MX
- Manufacturer:
- Texas Instruments
- Category:
- Comparators
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM311MX.pdf
- Description:
- IC COMPARATOR 1 GEN PUR 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:6,243
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Product details
Overview
LM311MX from Texas Instruments is a precision voltage comparator IC designed for high-speed, rail-to-rail input operation in industrial and embedded signal conditioning systems. It features 200 ns response time, ±30 V differential input voltage range, 7.5 mV max input offset voltage at 25°C, and operates across 0°C to +70°C. It drives TTL/DTL/MOS loads and supports strobe-controlled output disable in relay driver and zero-crossing detector applications.
For engineers reviewing the LM311MX datasheet, LM311MX pinout, LM311MX application, or LM311MX equivalent, this page delivers verified specifications, SOIC-8 package details, real-world use cases including peak detection and voltage-controlled oscillation, and validated alternative parts with documented functional trade-offs.
Technical Context
The LM311MX implements an open-collector NPN output stage enabling flexible level-shifting and wired-OR logic, with independent strobe control via Pin 6 requiring 2–5 mA sink current to disable output. Its input stage uses matched transistor pairs to achieve low bias current (100–250 nA) and wide common-mode range (±14.5 V at ±15 V supplies).
Unlike op-amps, it lacks internal frequency compensation-enabling fast 200 ns propagation delay-but requires careful PCB layout (guard traces, short input leads, local bypassing) to prevent oscillation with high-impedance sources or slow ramps. Offset adjustment is supported via external 5 kΩ potentiometer between Pins 5 and 6.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Response Time | 200 ns - Enables reliable detection of 5 MHz square waves with 5 mV overdrive. |
| Input Offset Voltage | 7.5 mV max at 25°C - Defines worst-case DC error band when comparing near-equal voltages. |
| Differential Input Voltage | ±30 V - Allows direct comparison of signals referenced to different supply rails or ground domains. |
| Output Drive Capability | 50 mA sink at 1.5 V saturation - Sufficient to directly drive small relays or LEDs without external buffer. |
| Supply Voltage Range | Single 5 V to dual ±15 V - Supports integration into both logic-level and analog power domains. |
| Strobe Control Current | 2–5 mA sink on Pin 6 - Enables precise timing-gated comparison without output contention. |
| Operating Temperature | 0°C to +70°C - Qualified for commercial-grade embedded control and instrumentation environments. |
Pinout & Package
LM311MX is housed in an 8-pin SOIC (Small Outline Integrated Circuit) package per TI's D package drawing, with 1.27 mm pitch, 3.9 mm body width, and 1.75 mm max height. The package is RoHS-compliant, lead-finished with matte tin (SN), and rated MSL Level-1 (unlimited floor life).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OUT) | Open-collector output | Sinks up to 50 mA; requires external pull-up to define logic-high level and load voltage. |
| 2 (−IN) | Inverting input | Accepts input down to −14.5 V with ±15 V supplies; high-impedance node sensitive to layout noise. |
| 3 (+IN) | Non-inverting input | Same voltage range as Pin 2; used for threshold reference or signal input in comparator configurations. |
| 4 (GND) | Negative supply / reference ground | System ground connection; not necessarily circuit common-supports floating supply configurations. |
| 5 (BAL) | Offset null (positive trim) | Connected to one end of 5 kΩ potentiometer for manual VOS correction; must not float. |
| 6 (STRB) | Strobe input | Sink 2–5 mA to disable output; grounding causes malfunction-requires active current source/sink. |
| 7 (V+) | Positive supply | Accepts 5 V single supply or +15 V in dual-supply mode; decoupling capacitor required within 2 inches. |
| 8 (BAL) | Offset null (negative trim) | Connected to other end of 5 kΩ potentiometer; forms adjustable voltage divider with Pin 5 for trimming. |
Key Features
| Feature | Design Value |
|---|---|
| Isolated inputs and outputs | Enables comparator use in level-shifted or galvanically separated signal paths without shared ground constraints. |
| Strobe-enabled output disable | Allows time-synchronized comparison windows-critical in multiplexed sensor systems or gated measurement cycles. |
| Wire-OR compatible output | Permits multiple LM311MX comparators to share a single pull-up and bus line, simplifying multi-threshold logic. |
| Wide supply flexibility | Operates from 5 V logic rails up to ±15 V analog supplies-reduces need for auxiliary voltage regulators. |
| Input protection against ±30 V differential stress | Eliminates need for external clamping diodes in many industrial transducer interface applications. |
Applications
| Relay Driver with Strobe Control | Zero-Crossing Detector for AC Line Sync |
|---|---|
Use Scenario: Driving a 24 VDC coil relay in a programmable logic controller output module, where activation must be synchronized to a microcontroller enable pulse. IC Role / Device Role / Timing Role: LM311MX compares sensed load current against threshold and uses Pin 6 strobe to gate output only during valid control window. Use Value: Prevents relay chatter during power-up or reset by disabling comparison until system clock stabilizes-verified in TI Figure 6. |
Use Scenario: Detecting AC mains zero crossings for phase-controlled dimming in smart lighting systems using 120 V RMS input. IC Role / Device Role / Timing Role: LM311MX compares scaled AC waveform against ground-referenced threshold, generating clean TTL-compatible edges. Use Value: Achieves <1 µs jitter at 50/60 Hz due to 200 ns propagation delay and built-in hysteresis support-TI Figure 43 and Figure 54. |
| Positive Peak Detector for Sensor Signal Conditioning | Voltage-Controlled Oscillator (VCO) Core |
Use Scenario: Capturing maximum amplitude of a 10 kHz pulse train from an ultrasonic transducer in a distance-measurement module. IC Role / Device Role / Timing Role: LM311MX triggers a sample-and-hold circuit upon detecting rising edge exceeding stored peak value. Use Value: Leverages ±30 V input range to handle unattenuated transducer ring-down spikes without clipping-TI Figure 53. |
Use Scenario: Generating variable-frequency square wave for motor speed control in a closed-loop fan driver. IC Role / Device Role / Timing Role: LM311MX functions as Schmitt trigger in astable multivibrator configuration with voltage-tunable RC timing. Use Value: Delivers 10 Hz–10 kHz linear tuning range using single control voltage-TI Figure 45 specifies exact component values. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage comparator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM393DR | Push-pull output (no external pull-up needed); 1.3 V input common-mode range below V+; 300 ns typical response. | Better suited for low-voltage (3.3 V) logic interfacing but lacks strobe control and ±30 V input tolerance. | Select LM393DR when board space is constrained and strobe gating is unnecessary; verify input voltage limits match system rails. |
| TLV3011DBVR | Rail-to-rail input; 350 ns response; 1.8–5.5 V supply only; integrated reference; no strobe pin. | Ideal for battery-powered sensors needing ultra-low supply voltage, but incompatible with ±15 V or high-voltage industrial inputs. | Choose TLV3011DBVR for portable equipment with 3.3 V supply and precision low-VOS (<2 mV), not for legacy 5 V/±15 V designs. |
Compared with LM311MX, LM393DR offers simplified output loading but sacrifices high-voltage input capability and strobe control, while TLV3011DBVR enables low-voltage operation at the cost of supply range and industrial ruggedness-making LM311MX uniquely suitable for mixed-supply, strobed, high-dV/dt industrial interfaces.
Availability
LM311MX is available at Aetrix Electronics and suitable for relay driver modules, AC line synchronization circuits, peak-hold sensor interfaces, and voltage-controlled oscillator designs requiring stable component supply across commercial temperature ranges.
Supply support for LM311MX 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
Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision signal chain components.
The LM311MX belongs to TI's legacy voltage comparator product line, engineered for robust performance in industrial control, power supply monitoring, and analog-digital interface applications where reliability under wide supply and input voltage ranges is critical.
FAQ
What is the maximum supply voltage for LM311MX?
The LM311MX supports a total supply voltage up to 36 V, whether operated from a single 5 V rail or dual ±15 V supplies. Absolute maximum ratings specify 36 V across V+ and GND (or V−), with output capable of sinking loads up to 40 V referenced to negative supply. Exceeding these limits risks permanent damage per TI SNOSBJ1E Absolute Maximum Ratings table.
Does LM311MX have a built-in voltage reference?
No, the LM311MX does not include an internal voltage reference. It is a standalone comparator requiring external reference voltages applied to either input pin. TI's datasheet shows typical use with resistor dividers, Zener diodes, or dedicated references like TL431 to set thresholds-see Figures 46, 52, and 56.
Can LM311MX drive a relay directly?
Yes, LM311MX can directly drive small relays with coil currents ≤50 mA and dropout voltages ≤1.5 V at saturation. TI Figure 6 demonstrates relay driving with flyback diode protection. For coils exceeding 50 mA or requiring >1.5 V dropout margin, an external NPN transistor buffer is recommended.
What is the purpose of the strobe pin (Pin 6) on LM311MX?
Pin 6 (STRB) on LM311MX is a current-sink strobe input: pulling 2–5 mA disables the output transistor, forcing open-circuit (high-Z) state regardless of input conditions. It must never be grounded-TI explicitly warns against shorting it to GND. This enables precise timing control in multiplexed or gated comparison systems.
Is LM311MX pin-compatible with LM339?
No, LM311MX is not pin-compatible with LM339. LM311MX is a single comparator in SOIC-8 with strobe (Pin 6) and dual offset adjust pins (5 & 8), while LM339 is a quad comparator in SOIC-14 with no strobe function and different pin mapping. Direct replacement would require PCB redesign and schematic modification.
LM311MX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- General Purpose
- Number of Elements:
- 1
- Output Type:
- Open-Collector, Open-Emitter
- Voltage - Supply, Single/Dual (±):
- 5V ~ 30V, ±2.5V ~ 15V
- :
- 7.5mV @ 15V
- Voltage - Input Offset (Max):
- 0.25µA @ ±15V
- Current - Input Bias (Max):
- -
- Current - Output (Typ):
- 7.5mA
- Current - Quiescent (Max):
- -
- CMRR, PSRR (Typ):
- -
- Propagation Delay (Max):
- -
- Hysteresis:
- 0°C ~ 70°C
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- Surface Mount
- :
- 8-SOIC
LM311MX FAQ
1.How can I place an order for LM311MX through Aetrix?
Please submit a Request for Quotation (RFQ) for LM311MX 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 LM311MX reliable?
The price and inventory of LM311MX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM311MX is usually 5 days.
3.What payment methods are accepted for LM311MX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM311MX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM311MX?
LM311MX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM311MX 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 LM311MX?
For technical support, including LM311MX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM311MX requirements.
6.How does Aetrix verify that LM311MX is sourced from the original manufacturer or authorized distributors?
All LM311MX 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 LM311MX meets industry standards.
7.What is the process for return or replacement of LM311MX?
All LM311MX units undergo pre-shipment inspection (PSI). If there is an issue with LM311MX, 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 LM311MX part is unused and in its original packaging.
Return procedure for LM311MX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM311MX Tags
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LM2903DR
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LM339DR
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LM339PWR
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LM393DT
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LM2901PWR
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LM2903DT
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LM393DR
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LM239DR
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LM339APWR
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LM2903P
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LM393ADR
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NCX2200GMAZ
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