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Texas Instruments LM311H
- Part No.:
- LM311H
- Manufacturer:
- Texas Instruments
- Category:
- Comparators
- Package:
- TO-99-8 Metal Can
- Datasheet:
-
LM311H.pdf
- Description:
- IC COMPARATOR 1 GEN PUR TO99-8
- Quantity:
- Payment:
- Shipping:
Inventory:439
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Product details
Overview
LM311H from Texas Instruments is a precision voltage comparator with open-collector output, designed for single-supply (5V) or dual-supply (±15V) operation in industrial and embedded signal conditioning. It delivers 200 ns response time, ±30V differential input range, 7.5 mV max input offset voltage at 25°C, and drives loads up to 50 mA - enabling direct relay and lamp control in power management circuits.
For engineers reviewing the LM311H datasheet, LM311H pinout, LM311H application, or LM311H equivalent, this page provides verified technical context, package-specific pin mapping for the TO-99 metal can, real-world design meaning of strobe and offset trim functions, and two validated alternative comparators with documented thermal and bias current differences.
Technical Context
The LM311H uses a bipolar input stage with trimmed offset and strobe-controlled output disable, allowing isolation from system ground and compatibility with TTL/DTL/RTL logic families. Its open-collector output supports level-shifting across supply domains (up to 40V referenced to negative supply) and wire-OR capability.
It features dedicated offset null pins (5 and 6) and a strobe pin (7) requiring 2–5 mA sink current to disable output - not ground connection. Input bias current remains ≤250 nA over 0°C to +70°C, and common-mode input range extends to ±14.5 V with ±15 V supplies.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | Single 5V or dual ±15V - enables direct interface with logic ICs and analog sensors without level shifters. |
| Response Time | 200 ns (100 mV step, 5 mV overdrive) - suitable for medium-speed zero-crossing detection and PWM generation. |
| Input Offset Voltage | 7.5 mV max at 25°C - defines minimum detectable voltage difference before output switching. |
| Differential Input Voltage | ±30V - allows direct comparison of signals referenced to different potentials, e.g., motor phase voltages. |
| Output Drive Capability | 50 mA sink, 40V max output-to-negative-supply - supports direct driving of relays, LEDs, and MOSFET gates. |
| Strobe Control Current | 2.0–5.0 mA sink required on Pin 7 - enables synchronized blanking of comparator output during critical timing windows. |
| Operating Temperature | 0°C to +70°C - qualified for commercial-grade embedded systems, not extended industrial or automotive environments. |
Pinout & Package
LM311H is housed in an 8-pin TO-99 metal can package (LMC outline), hermetically sealed for enhanced reliability in harsh environments. The package includes internal thermal path to case and is lead-free compliant (NOPB suffix).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Emitter) | Negative supply return / Output collector reference | Internally connected to NPN output transistor emitter; must be tied to V− or ground depending on load configuration. |
| 2 (Inverting Input) | Comparator inverting input | High-impedance bipolar input node; accepts signals within ±14.5 V of V− with ±15 V supplies. |
| 3 (Non-inverting Input) | Comparator non-inverting input | High-impedance bipolar input node; used for threshold reference or signal comparison. |
| 4 (V−) | Negative supply pin | Accepts −15 V or ground; sets lower rail for internal circuitry and output stage reference. |
| 5 (Offset Null) | Offset null adjustment terminal | Connects to one end of 5 kΩ potentiometer for trimming input offset voltage to <1 mV. |
| 6 (Offset Null) | Offset null adjustment terminal | Connects to other end of 5 kΩ potentiometer; center wiper goes to V+ or V− per datasheet Figure 1. |
| 7 (Strobe) | Output enable/disable control | Sink 3–5 mA to disable output; floating or pulled high enables normal operation - prevents false triggering during power-up. |
| 8 (V+) | Positive supply pin | Accepts +5 V or +15 V; powers internal circuitry and defines upper rail for output saturation. |
Key Features
| Feature | Design Value |
|---|---|
| Open-collector output | Enables level-shifting, wire-OR logic, and direct drive of 40V/50mA loads without external pull-up constraints. |
| Strobe-enabled output disable | Allows precise temporal blanking of comparator decisions - critical in multiplexed sensing or synchronous sampling systems. |
| Offset null terminals | Supports active trimming of input offset to sub-millivolt levels, improving accuracy in precision threshold detection. |
| Wide supply range | Operates from 5V single supply to ±15V dual supply - eliminates need for separate analog/digital rails in mixed-signal designs. |
| Input isolation from ground | Both inputs float relative to system ground, enabling high-side sensing and differential measurements in grounded-load configurations. |
Applications
| Relay Control Interface | Zero-Crossing Detection |
|---|---|
Use Scenario: Driving electromagnetic relays in AC mains monitoring systems where isolation and high-voltage tolerance are required. IC Role / Device Role / Timing Role: Voltage comparator detecting when AC line voltage crosses 0 V with hysteresis to suppress noise-induced chatter. Use Value: Direct 50 mA output sink eliminates need for driver transistors; ±30V input range accommodates full AC waveform without attenuation. |
Use Scenario: Synchronizing microcontroller interrupts or TRIAC firing in dimmer and motor control applications. IC Role / Device Role / Timing Role: Precision comparator generating clean digital edges at AC zero crossings with minimal propagation delay variation. Use Value: 200 ns response time ensures consistent edge placement; strobe pin allows blanking during transient events near zero crossing. |
| Voltage-Controlled Oscillator (VCO) | Threshold-Based Sensor Interface |
Use Scenario: Building tunable square-wave oscillators in function generators or clock recovery circuits using resistor-capacitor feedback. IC Role / Device Role / Timing Role: Comparator with hysteresis forming the core of an astable multivibrator; output frequency set by RC time constant and reference voltage. Use Value: Adjustable offset null pins allow fine-tuning of duty cycle symmetry; open-collector output simplifies integration with CMOS/TTL logic stages. |
Use Scenario: Converting analog sensor outputs (e.g., thermistor, photodiode) into digital alerts when thresholds are exceeded. IC Role / Device Role / Timing Role: High-input-impedance comparator comparing sensor voltage against stable reference, with strobe used for periodic sampling. Use Value: Input bias current ≤250 nA minimizes loading error on high-impedance sensors; 7.5 mV offset ensures reliable detection of small signal excursions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage comparator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM311MX/NOPB | SOIC-8 package; 0°C to +70°C rating; 300 nA max input bias current at 25°C vs. 250 nA for LM311H | Surface-mount assembly; higher thermal resistance (100°C/W junction-to-ambient) vs. TO-99's superior heat dissipation | Select LM311MX/NOPB for automated PCB assembly; LM311H preferred for high-reliability, thermally constrained, or hermetic requirements. |
| LM393DR | Push-pull output (no external pull-up needed); 2 mV max input offset; dual-channel; 1.2 mA supply current vs. 6 mA for LM311H | Lower power, no strobe or offset null pins; limited to 36 V total supply, no 40 V output swing capability | Choose LM393DR for low-power dual-comparator needs without strobe or high-voltage drive; LM311H retains advantage in relay driving and isolated sensing. |
Compared with LM311MX/NOPB and LM393DR, the LM311H offers unique hermetic TO-99 packaging, strobe control, offset trimming, and 40 V output swing - making it irreplaceable in legacy industrial controls, high-voltage isolation interfaces, and applications requiring long-term parameter stability under thermal cycling.
Availability
LM311H is available at Aetrix Electronics and suitable for relay drivers, zero-crossing detectors, voltage-controlled oscillators, and threshold-based sensor interfaces requiring stable component supply across commercial temperature ranges.
Supply support for LM311H 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 delivering analog and embedded processing solutions, with over 50 years of innovation in precision linear ICs and industrial-grade components.
The LM311H belongs to TI's legacy precision comparator family, engineered for robust performance in industrial automation, power supply monitoring, and analog signal conditioning where reliability, wide supply range, and output drive strength are critical.
FAQ
What is the maximum output voltage swing capability of the LM311H?
The LM311H output can swing up to 40 V referenced to the negative supply pin (Pin 1), as specified in its Absolute Maximum Ratings for the LM311-N series. This allows direct driving of 24 V or 36 V relay coils without external level-shifting circuitry. The LM311H achieves this via its open-collector NPN output stage, which requires an external pull-up to the desired positive rail. Operation beyond 40 V risks permanent damage.
Can the LM311H operate from a single 5V supply?
Yes, the LM311H is explicitly rated for single 5V supply operation per its datasheet Features and Electrical Characteristics tables. With V+ = 5V and V− = 0V (ground), it maintains functional input common-mode range (−0.3 V to 3.7 V), 0.4 V typical saturation voltage at 8 mA load, and full strobe and offset null functionality. This makes LM311H suitable for mixed-signal systems powered solely by 5V logic rails.
How is the strobe pin (Pin 7) of the LM311H correctly implemented?
The strobe pin (Pin 7) of the LM311H must be actively sunk with 2–5 mA current to disable the output - it must never be grounded directly. A typical implementation uses an NPN transistor or logic gate output pulling Pin 7 low through a current-limiting resistor (e.g., 1 kΩ with 5V pull-up yields ~4 mA). When strobe current is removed, the output resumes normal comparator operation. Incorrect grounding causes undefined behavior and potential damage.
What is the purpose of Pins 5 and 6 on the LM311H?
Pins 5 and 6 on the LM311H are offset null terminals used to adjust input offset voltage to sub-millivolt levels. A 5 kΩ potentiometer is connected between these pins, with its wiper tied to V+ (for V+ ≥ 5V) or V−. This trims the internal input stage imbalance, critical in precision threshold detection where even 5 mV offset could cause erroneous triggering. If unused, Pins 5 and 6 should be shorted together to prevent noise coupling.
Is the LM311H pin-compatible with the LM311N/NOPB in PDIP packaging?
No - the LM311H (TO-99 metal can, 8-pin) and LM311N/NOPB (PDIP, 8-pin) share identical electrical functionality and pin numbering, but their physical footprints and thermal characteristics differ significantly. The TO-99 package has a circular land pattern with center tab, while PDIP uses rectangular DIP layout. PCB layout, thermal vias, and mechanical mounting are not interchangeable; redesign is required when substituting between these packages.
LM311H Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- TO-99-8 Metal Can
- Series:
- -
- Packaging:
- Box
- 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 ~ 36V, ±2.5V ~ 18V
- :
- 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:
- Through Hole
- :
- TO-99-8
LM311H FAQ
1.How can I place an order for LM311H through Aetrix?
Please submit a Request for Quotation (RFQ) for LM311H 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 LM311H reliable?
The price and inventory of LM311H are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM311H is usually 5 days.
3.What payment methods are accepted for LM311H?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM311H transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM311H?
LM311H orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM311H 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 LM311H?
For technical support, including LM311H datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM311H requirements.
6.How does Aetrix verify that LM311H is sourced from the original manufacturer or authorized distributors?
All LM311H 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 LM311H meets industry standards.
7.What is the process for return or replacement of LM311H?
All LM311H units undergo pre-shipment inspection (PSI). If there is an issue with LM311H, 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 LM311H part is unused and in its original packaging.
Return procedure for LM311H:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM311H Tags
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LM2903P
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