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STMicroelectronics LM311DT
- Part No.:
- LM311DT
- Manufacturer:
- STMicroelectronics
- Category:
- Comparators
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM311DT.pdf
- Description:
- IC COMPARATOR 1 GEN PUR 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:10,313
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Product details
Overview
LM311DT from STMicroelectronics is a single high-speed voltage comparator with strobe input, designed for precision level detection in analog-to-digital interfaces and threshold monitoring circuits. It features ±30 V differential input voltage range, 50 mA output sink current, 200 ns response time at 100 mV step, and operates from +5 V to ±15 V supplies. Used in overvoltage protection circuits for industrial power supplies.
For engineers reviewing the LM311DT datasheet, LM311DT pinout, LM311DT application, or LM311DT equivalent, key selection criteria include strobe-controlled output gating, wide supply flexibility (+5 V single-rail or ±15 V dual-rail), TTL/RTL/MOS-compatible open-collector output, and guaranteed performance across 0 °C to +70 °C ambient.
Technical Context
The LM311DT implements a bipolar transistor-based comparator core with internal compensation and a dedicated strobe (pin 6) that forces the output high-impedance state when active low. Its input stage uses matched PNP transistors to achieve low input bias current (≤300 nA max) and low offset current (≤70 nA max) across temperature.
Output stage is an open-collector NPN transistor rated for 50 mA sink current and up to +40 V output-to-negative-supply voltage (LM311DT variant). Strobe functionality enables synchronized sampling and noise-immune window detection in multiplexed sensor systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | +5 V to ±15 V - supports direct interface with TTL logic and legacy op-amp rails |
| Response Time | 200 ns - enables accurate edge detection in pulse-width modulation feedback loops |
| Differential Input Range | ±30 V - allows direct comparison of signals referenced to different supply domains |
| Output Sink Current | 50 mA - drives relays, LEDs, or logic inputs without external buffer stages |
| Input Offset Voltage | ≤10 mV - defines minimum detectable voltage difference under worst-case conditions |
| Strobe Input Logic | Active-low control - disables output (high-Z) to prevent false triggering during signal settling |
Pinout & Package
LM311DT is housed in an SO-8 plastic micropackage (ECOPACK® compliant), 1.27 mm pitch, with exposed pad not connected internally. Pinout follows standard industry configuration for single comparators with strobe.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Offset Null | Adjusts input offset voltage via external potentiometer; unused in most applications |
| 2 | Inverting Input (−) | Reference or threshold input node; accepts voltages within common-mode range |
| 3 | Non-inverting Input (+) | Signal input node; differential pair base connection for comparison decision |
| 4 | V− (GND/Negative Supply) | Power return path; tied to 0 V for single-supply operation or negative rail in dual supply |
| 5 | V+ (Positive Supply) | Main power input; supports +5 V only or ±15 V dual-rail configurations |
| 6 | Strobe | Active-low enable: pulls output high-Z when logic low; critical for synchronized sampling |
| 7 | Output | Open-collector NPN collector; requires external pull-up to define logic HIGH level |
| 8 | Compensation | Internal compensation node; no external components required for stable operation |
Key Features
| Feature | Design Value |
|---|---|
| Wide Supply Range | +5 V single supply or ±15 V dual supply - eliminates need for level-shifting circuitry |
| Strobe-Controlled Output | Pin 6 forces high-impedance output state - enables time-gated comparisons in multiplexed systems |
| High Output Drive | 50 mA sink capability - directly interfaces with electromechanical loads and logic families |
| Low Input Bias Current | ≤300 nA max - preserves signal integrity in high-impedance sensor front-ends |
Applications
| Overvoltage Protection | Pulse Width Modulation Feedback |
|---|---|
Use Scenario: Monitoring DC bus voltage in switch-mode power supplies to trigger shutdown before capacitor overvoltage. IC Role / Device Role / Timing Role: Precision threshold detector comparing sensed voltage against reference; strobe used to sample only during stable PWM off-time. Use Value: Prevents catastrophic failure by enabling fast (<200 ns) response to transient overvoltage events while rejecting switching noise via strobe gating. | Use Scenario: Measuring duty cycle of motor control PWM signals in real time for closed-loop speed regulation. IC Role / Device Role / Timing Role: Edge-triggered comparator converting PWM waveform into clean digital timing pulses for microcontroller capture peripherals. Use Value: Delivers deterministic 200 ns propagation delay and TTL-compatible output, ensuring accurate period measurement independent of supply rail variations. |
| Zero-Crossing Detection | Window Comparator Interface |
Use Scenario: Detecting AC line zero-crossing points for phase-controlled dimming and solid-state relay timing. IC Role / Device Role / Timing Role: High-common-mode-rejection comparator sensing small differential voltage across current-sense resistor near ground potential. Use Value: ±30 V differential input range accommodates full AC waveform swing without attenuation; low offset ensures sub-10 mV trip point accuracy. | Use Scenario: Validating sensor output lies within safe operating bounds (e.g., temperature or pressure transducer range). IC Role / Device Role / Timing Role: One half of dual-comparator window circuit; strobe synchronizes validation window to system clock edges. Use Value: Strobe input enables precise temporal alignment of window evaluation, eliminating metastability in safety-critical monitoring paths. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage comparator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM393DT | Dual comparator, lower supply current (0.8 mA vs 11 mA), no strobe function, 1.3 V input common-mode range limit | Suitable for low-power, non-synchronized dual-threshold detection; lacks strobe for noise-immune sampling | Select when dual-channel operation and ultra-low quiescent current outweigh need for strobe control and wide input range |
| TL331IDT | Single comparator, rail-to-rail input, 60 µA supply current, no strobe, 36 V max supply | Better for battery-powered systems requiring rail-to-rail sensing; missing strobe limits use in noisy multiplexed environments | Choose when input signal spans full supply range and power budget is constrained, but strobe gating is unnecessary |
Compared with LM311DT, LM393DT offers dual-channel density and lower power but sacrifices strobe control and ±30 V input range; TL331IDT provides rail-to-rail input and micropower operation yet omits strobe and high-output-drive capability essential for industrial actuator interfacing.
Availability
LM311DT is available at Aetrix Electronics and suitable for overvoltage protection, PWM feedback monitoring, and zero-crossing detection requiring stable component supply across industrial control, power conversion, and embedded instrumentation programs.
Supply support for LM311DT 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering intelligent power, sensing, and control solutions for automotive, industrial, and consumer markets.
The LM311DT belongs to ST's legacy analog comparator product line, engineered specifically for robust, high-speed level detection in harsh electrical environments where strobe synchronization and wide supply tolerance are mandatory.
FAQ
What is the maximum output voltage the LM311DT can switch?
The LM311DT output transistor supports up to +40 V between pin 7 (output) and pin 4 (V−) under continuous operation. This allows direct driving of 24 V industrial logic or optocouplers without level-shifting circuitry, provided the external pull-up resistor is rated for the applied voltage and power dissipation.
Does the LM311DT require external compensation components?
No. The LM311DT integrates internal frequency compensation and operates stably without external capacitors or resistors. Pin 8 (compensation) is an internal node and must remain unconnected; adding external components may destabilize the comparator or degrade response time.
Can the LM311DT operate from a single +3.3 V supply?
No. The LM311DT minimum specified supply is +5 V for single-rail operation. At +3.3 V, internal transistor biasing fails, resulting in undefined output behavior, excessive propagation delay (>1 µs), and inability to meet datasheet parameters including offset voltage and response time.
How does the strobe pin affect output state during activation?
When the strobe pin (pin 6) is pulled low, the output transistor turns OFF, placing pin 7 in high-impedance state regardless of input differential voltage. When strobe returns high, output resumes normal comparison behavior after a typical 150 ns recovery delay, enabling precise time-windowed signal evaluation.
LM311DT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- General Purpose
- Number of Elements:
- 1
- Output Type:
- DTL, MOS, Open-Collector, Open-Emitter, RTL, TTL
- Voltage - Supply, Single/Dual (±):
- 5V ~ 30V, ±2.5V ~ 15V
- :
- 7.5mV @ ±15V
- Voltage - Input Offset (Max):
- 0.25µA @ ±15V
- Current - Input Bias (Max):
- 50mA
- 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
LM311DT FAQ
1.How can I place an order for LM311DT through Aetrix?
Please submit a Request for Quotation (RFQ) for LM311DT 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 LM311DT reliable?
The price and inventory of LM311DT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM311DT is usually 5 days.
3.What payment methods are accepted for LM311DT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM311DT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM311DT?
LM311DT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM311DT 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 LM311DT?
For technical support, including LM311DT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM311DT requirements.
6.How does Aetrix verify that LM311DT is sourced from the original manufacturer or authorized distributors?
All LM311DT 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 LM311DT meets industry standards.
7.What is the process for return or replacement of LM311DT?
All LM311DT units undergo pre-shipment inspection (PSI). If there is an issue with LM311DT, 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 LM311DT part is unused and in its original packaging.
Return procedure for LM311DT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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