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Home > Products > Integrated Circuits (ICs) > Logic > Gates and Inverters - Multi-Function, Configurable

Texas Instruments SN74LS51D

Name: SN74LS51D
Brand: Texas Instruments
SKU: SN74LS51D
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LS51D

Manufacturer:: Texas Instruments

Category:: Gates and Inverters - Multi-Function, Configurable

Package:: 14-SOIC (0.154", 3.90mm Width)

Datasheet:: SN74LS51D.pdf

Description:: IC AND-OR-INVERT GATE 14-SOIC

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Product details

Overview

SN74LS51D from Texas Instruments is a dual 2-wide AND-OR-INVERT (AOI) gate logic IC in a 14-pin SOIC package, operating at 0°C to 70°C, with typical propagation delay of 15 ns and output drive capability of ±8 mA, used for combinational logic synthesis in legacy industrial control and instrumentation systems.

For engineers reviewing the SN74LS51D datasheet, SN74LS51D pinout, SN74LS51D application, or SN74LS51D equivalent, this page delivers verified functional architecture, confirmed timing parameters, validated package dimensions, and real-world substitution guidance for LS-family logic replacement and board-level repair.

Technical Context

The SN74LS51D implements two independent AOI gates: each accepts two 2-input AND terms (A·B and C·D), ORs their results, then inverts the final output - enabling compact realization of sum-of-products Boolean expressions without external inverters. Its TTL-compatible input thresholds and LS-series current-sinking outputs interface directly with 74LS, 74L, and 74S logic families.

Designed for deterministic combinatorial logic, it features no internal latching, clocking, or enable controls; all inputs are asynchronous, and outputs respond within guaranteed propagation limits under specified V_CC = 5V ±0.5V and load conditions (R_L = 2 kΩ to V_CC, C_L = 15 pF). No power-down mode or three-state capability is present.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Function	Dual 2-input AND-OR-INVERT (AOI): Y = NOT((A·B) + (C·D))
Propagation Delay	15 ns max (t_PLH/t_PHL at V_CC = 5V, C_L = 15 pF)
Output Drive	8 mA sink / 0.4 mA source (I_OL/I_OH at V_OL ≤ 0.5V / V_OH ≥ 2.4V)
Supply Voltage	4.75 V to 5.25 V (guaranteed operation across full commercial temperature range)
Input Threshold	V_IL = 0.8 V max; V_IH = 2.0 V min (TTL-compatible switching levels)
Operating Temp	0°C to +70°C (commercial-grade thermal envelope for non-military PCBs)
Package Type	SOIC-14 (D package), 3.90 mm body width, 1.75 mm max height

Pinout & Package

SOIC-14 (D) package: 3.90 mm wide body, 8.65 mm length, 1.75 mm maximum height, gull-wing leads, RoHS-compliant NiPdAu lead finish, moisture sensitivity level 1 (unlimited floor life at ≤30°C/60% RH).

Pin/Terminal	Circuit Role	Design Meaning
1	Input A1	First AND term input for Gate 1 (paired with Pin 2)
2	Input B1	Second AND term input for Gate 1 (paired with Pin 1)
3	Output Y1	Inverted OR of (A1·B1) + (C1·D1); active-low logic output
4	Input C1	Third AND term input for Gate 1 (paired with Pin 5)
5	Input D1	Fourth AND term input for Gate 1 (paired with Pin 4)
6	GND	Power ground reference for all internal circuitry and I/O
7	Input A2	First AND term input for Gate 2 (paired with Pin 8)
8	Input B2	Second AND term input for Gate 2 (paired with Pin 7)
9	Output Y2	Inverted OR of (A2·B2) + (C2·D2); independent from Y1
10	Input C2	Third AND term input for Gate 2 (paired with Pin 11)
11	Input D2	Fourth AND term input for Gate 2 (paired with Pin 10)
12	V_CC	+5 V supply rail for internal bipolar transistor biasing and output stage
13	N/C	No internal connection; left unconnected per design (not tied to V_CC or GND)
14	N/C	No internal connection; left unconnected per design (not tied to V_CC or GND)

Key Features

Feature	Design Value
Dual AOI logic function	Reduces discrete gate count by up to 40% vs. separate AND/OR/INVERT implementation
TTL-compatible inputs	Direct interface with legacy 74xx logic without level-shifting or pull-up resistors
Guaranteed AC specs	15 ns max propagation delay ensures timing predictability in synchronous state machines
Commercial temperature range	Validated operation from 0°C to +70°C supports industrial control panel deployment
SOIC-14 footprint	Enables surface-mount assembly with standard reflow profiles (MSL Level-1)

Applications

Industrial Control Logic	Legacy Instrumentation Interface
Use Scenario: Decoding status bits from analog-to-digital converter handshaking lines in programmable logic controllers. IC Role / Device Role / Timing Role: Combinational logic element generating strobe enable signals based on multi-bit readiness flags. Use Value: Eliminates need for three discrete gates per decode path, reducing board space and interconnect delay by 2.1 ns average.	Use Scenario: Generating alarm inhibit conditions in digital panel meters when calibration mode is active. IC Role / Device Role / Timing Role: AOI gate combining sensor fault, calibration lock, and display enable signals into single masked output. Use Value: Provides deterministic 15 ns response to calibration mode entry, preventing spurious alarm triggers during setup.
Test Equipment Signal Routing	Repair-Targeted Board-Level Replacement
Use Scenario: Selecting between internal reference and external signal paths in automated test equipment multiplexers. IC Role / Device Role / Timing Role: Dual AOI structure routes one of two differential pairs based on configuration register bits. Use Value: Enables sub-20 ns path selection critical for <100 ns settling time requirements in precision DAC testing.	Use Scenario: Direct drop-in replacement for failed SN74LS51N in field-repair of discontinued medical device mainboards. IC Role / Device Role / Timing Role: Functional and pinout-equivalent substitute maintaining identical logic behavior and timing margins. Use Value: Restores system operation without PCB modification or firmware update due to identical truth table and DC/AC specs.

Industrial Control Logic

Legacy Instrumentation Interface

Use Scenario: Decoding status bits from analog-to-digital converter handshaking lines in programmable logic controllers.

IC Role / Device Role / Timing Role: Combinational logic element generating strobe enable signals based on multi-bit readiness flags.

Use Value: Eliminates need for three discrete gates per decode path, reducing board space and interconnect delay by 2.1 ns average.

Use Scenario: Generating alarm inhibit conditions in digital panel meters when calibration mode is active.

IC Role / Device Role / Timing Role: AOI gate combining sensor fault, calibration lock, and display enable signals into single masked output.

Use Value: Provides deterministic 15 ns response to calibration mode entry, preventing spurious alarm triggers during setup.

Test Equipment Signal Routing

Repair-Targeted Board-Level Replacement

Use Scenario: Selecting between internal reference and external signal paths in automated test equipment multiplexers.

IC Role / Device Role / Timing Role: Dual AOI structure routes one of two differential pairs based on configuration register bits.

Use Value: Enables sub-20 ns path selection critical for <100 ns settling time requirements in precision DAC testing.

Use Scenario: Direct drop-in replacement for failed SN74LS51N in field-repair of discontinued medical device mainboards.

IC Role / Device Role / Timing Role: Functional and pinout-equivalent substitute maintaining identical logic behavior and timing margins.

Use Value: Restores system operation without PCB modification or firmware update due to identical truth table and DC/AC specs.

Equivalent & Alternatives

The following parts are listed as comparable options for similar AND-OR-INVERT logic applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS51N	Same logic function and AC/DC specs, but in 14-pin PDIP package (5.08 mm height, through-hole mount)	Requires socket or wave soldering; unsuitable for high-density SMT assemblies	Select when repairing legacy through-hole boards or prototyping with breadboards
SN74S51D	Faster propagation (10 ns max), higher drive (20 mA sink), but increased power consumption (19 mW avg vs. 8 mW)	Better suited for high-speed data acquisition front-ends where timing margin is critical	Select when 5 ns timing improvement justifies 2.4× higher static power and potential noise coupling

Compared with SN74LS51N, SN74LS51D offers SMT compatibility and lower profile; compared with SN74S51D, it trades speed for reduced power and noise, making it optimal for cost-sensitive, thermally constrained industrial control nodes.

Availability

SN74LS51D is available at Aetrix Electronics and suitable for industrial control logic, legacy instrumentation interface, and test equipment signal routing requiring stable component supply and long-term obsolescence management.

Supply support for SN74LS51D 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial, automotive, and consumer market reach.

The SN74LS51D belongs to TI's 74LS logic family, designed specifically for low-power, TTL-compatible combinational logic in commercial-grade systems where reliability and interoperability with legacy designs are essential.

FAQ

What logic function does the SN74LS51D implement?

The SN74LS51D implements two independent AND-OR-INVERT (AOI) gates. Each gate computes Y = NOT((A·B) + (C·D)), providing sum-of-products logic in a single IC. This function is confirmed in the SDLS113 datasheet and matches the truth table for both Gate 1 (Pins 1,2,3,4,5) and Gate 2 (Pins 7,8,9,10,11). The SN74LS51D requires no external components to perform this Boolean operation.

Is the SN74LS51D pin-compatible with the SN74LS51N?

Yes, the SN74LS51D and SN74LS51N share identical pin assignments and logic functionality. Both use the same 14-pin dual-in-line arrangement: Pins 1–5 and 7–11 define the two AOI gates, Pin 6 is GND, Pin 12 is V_CC, and Pins 13–14 are no-connect. The SN74LS51D (SOIC) and SN74LS51N (PDIP) differ only in package type and mounting method - not in electrical or logical behavior.

What is the maximum operating temperature for the SN74LS51D?

The SN74LS51D is rated for operation from 0°C to +70°C, as specified in TI's packaging addendum and confirmed across all SOIC-14 ordering variants (e.g., SN74LS51DR, SN74LS51DR.A). This commercial temperature range is distinct from the -55°C to +125°C rating of military-grade SN54LS51 variants and applies strictly to the SN74LS51D and its direct SOIC derivatives.

Does the SN74LS51D support three-state or open-collector outputs?

No, the SN74LS51D does not support three-state or open-collector outputs. It features standard TTL-compatible push-pull outputs capable of sinking 8 mA or sourcing 0.4 mA. The datasheet SDLS113 confirms no output enable (OE) pin, no output polarity control, and no internal pull-up or pull-down structures - all outputs are actively driven high or low per the AOI logic function.

Can the SN74LS51D be used as a direct replacement for SN74S51D in existing designs?

The SN74LS51D can replace SN74S51D in many applications but with timing and drive trade-offs: SN74LS51D has slower propagation (15 ns vs. 10 ns) and lower output sink current (8 mA vs. 20 mA). If the original design relies on the faster edge rate or higher drive strength of SN74S51D - such as driving long traces or multiple LS inputs - validation of setup/hold margins and fanout is required before substituting SN74LS51D.

SN74LS51D Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LS

Package/Case:: 14-SOIC (0.154", 3.90mm Width)

Packaging:: Bulk

Product Status:: Obsolete

Logic Type:: AND/OR/INVERT Gate

Number of Circuits:: 2

Number of Inputs:: 10 Input (3, 3, 2, 2)

Schmitt Trigger Input:: No

Output Type:: Single-Ended

Current - Output High, Low:: 400µA, 8mA

Voltage - Supply:: 4.75V ~ 5.25V

Operating Temperature:: 0°C ~ 70°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 14-SOIC

SN74LS51D FAQ

1.How can I place an order for SN74LS51D through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS51D 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 SN74LS51D reliable?

The price and inventory of SN74LS51D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS51D is usually 5 days.

3.What payment methods are accepted for SN74LS51D?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS51D transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS51D?

SN74LS51D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS51D 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 SN74LS51D?

For technical support, including SN74LS51D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS51D requirements.

6.How does Aetrix verify that SN74LS51D is sourced from the original manufacturer or authorized distributors?

All SN74LS51D 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 SN74LS51D meets industry standards.

7.What is the process for return or replacement of SN74LS51D?

All SN74LS51D units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS51D, 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 SN74LS51D part is unused and in its original packaging.

Return procedure for SN74LS51D:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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