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Texas Instruments SN74LS684N
- Part No.:
- SN74LS684N
- Manufacturer:
- Texas Instruments
- Category:
- Comparators
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS684N.pdf
- Description:
- IC COMPARATOR MAG 8BIT 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,823
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Product details
Overview
SN74LS684N from Texas Instruments is a 8-bit magnitude comparator IC in PDIP-20 package, operating from 4.75 V to 5.25 V with typical propagation delay of 25 ns and output drive capability of ±8 mA. It performs high-speed digital comparison of two 8-bit binary words and is used in address decoding, arithmetic logic units, and bus arbitration circuits.
For engineers reviewing the SN74LS684N datasheet, SN74LS684N pinout, SN74LS684N application, or SN74LS684N equivalent, key selection considerations include its TTL-compatible input thresholds, active-low outputs (A<B, A=B, A>B), 0°C to 70°C commercial temperature range, and direct compatibility with other 74LS family comparators in legacy control systems.
Technical Context
The SN74LS684N implements cascaded 8-bit magnitude comparison using internal AND-OR logic to generate three mutually exclusive active-low outputs: A<B, A=B, and A>B. It accepts two parallel 8-bit inputs (A₀–A₇ and B₀–B₇) and supports hierarchical expansion via cascading inputs (IA<B, IA=B, IA>B) for wider-word comparisons.
Designed for TTL logic families, it features standard LS-series DC characteristics: VIH = 2.0 V min, VIL = 0.8 V max, VOH = 2.7 V min at IOL = –0.4 mA, and VOL = 0.5 V max at IOH = 8 mA. Its internal architecture avoids latching and provides combinational output behavior with no internal clock or state retention.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | 8-bit magnitude comparator with cascading inputs and active-low outputs |
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation within standard TTL power rail tolerances |
| Propagation Delay | 25 ns typical - enables use in 20 MHz+ synchronous bus systems with tight timing budgets |
| Output Drive | ±8 mA - directly interfaces with multiple 74LS inputs without external buffering |
| Input Thresholds | VIH = 2.0 V min, VIL = 0.8 V max - guarantees noise immunity and compatibility across LS/TTL logic families |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded control and instrumentation applications |
| Package | PDIP-20 - through-hole mounting compatible with legacy PCB assembly and prototyping workflows |
Pinout & Package
SN74LS684N uses a 20-pin plastic dual in-line package (PDIP) with 0.3-inch body width and standard 0.1-inch pin pitch. Pin 1 is located at the top-left corner adjacent to the notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | A₀ | Least significant bit of input word A |
| 2 | A₁ | Second LSB of input word A |
| 3 | A₂ | Third LSB of input word A |
| 4 | A₃ | Fourth LSB of input word A |
| 5 | A₄ | Fifth LSB of input word A |
| 6 | A₅ | Sixth LSB of input word A |
| 7 | A₆ | Seventh LSB of input word A |
| 8 | A₇ | Most significant bit of input word A |
| 9 | GND | Power ground reference for all internal logic and output stages |
| 10 | B₇ | Most significant bit of input word B |
| 11 | B₆ | Seventh LSB of input word B |
| 12 | B₅ | Sixth LSB of input word B |
| 13 | B₄ | Fifth LSB of input word B |
| 14 | B₃ | Fourth LSB of input word B |
| 15 | B₂ | Third LSB of input word B |
| 16 | B₁ | Second LSB of input word B |
| 17 | B₀ | Least significant bit of input word B |
| 18 | IA>B | Cascading input asserting "A greater than B" from higher-order stage |
| 19 | IA=B | Cascading input asserting "A equal to B" from higher-order stage |
| 20 | VCC | +5 V supply for all internal gates and output drivers |
Key Features
| Feature | Design Value |
|---|---|
| Three independent active-low outputs | Simultaneous A<B, A=B, A>B signals enable priority encoding and status flag generation without external logic |
| Cascadable architecture | Supports multi-byte comparison by chaining multiple SN74LS684N devices with minimal interconnect |
| TTL-compatible input/output levels | Direct drop-in replacement for other 74LS comparators without level-shifting circuitry |
| No internal latches or clocks | Combinational behavior ensures deterministic timing and eliminates metastability concerns in synchronous designs |
| Standard PDIP-20 footprint | Enables use in breadboard-based development, repair of legacy equipment, and manual rework scenarios |
Applications
| Address Decoding | Bus Arbitration |
|---|---|
Use Scenario: Selecting memory or peripheral devices on an 8-bit microprocessor bus based on address range. IC Role / Device Role / Timing Role: SN74LS684N compares CPU address lines against fixed decode boundaries and asserts chip-select signals. Use Value: Enables precise 8-bit address window matching with sub-25 ns decision latency, reducing bus contention in multi-peripheral systems. | Use Scenario: Resolving simultaneous access requests from multiple DMA controllers sharing a common data bus. IC Role / Device Role / Timing Role: SN74LS684N evaluates priority-encoded request IDs and grants bus access to the highest-priority requester. Use Value: Provides deterministic, race-free arbitration using hardwired logic-no firmware overhead or interrupt latency. |
| Arithmetic Logic Unit (ALU) | Industrial Control Sequencing |
Use Scenario: Generating status flags (zero, carry, sign) during 8-bit arithmetic operations in discrete-logic ALUs. IC Role / Device Role / Timing Role: SN74LS684N compares ALU result against zero or test constants to drive condition-code registers. Use Value: Delivers cycle-accurate flag generation synchronized to ALU output, supporting pipelined instruction execution. | Use Scenario: Monitoring sensor register values against programmable thresholds in PLC I/O modules. IC Role / Device Role / Timing Role: SN74LS684N compares real-time analog-to-digital converted values against stored setpoints. Use Value: Enables immediate hardware-level response to out-of-range conditions without CPU intervention or polling delays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-bit magnitude comparator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS682N | Same 8-bit function but lacks cascading inputs (IA<B, IA=B, IA>B pins omitted) | Restricted to standalone 8-bit comparison; cannot expand to 16-/24-bit words | Select when only single-word comparison is required and board space is constrained |
| SN74LS688N | Includes open-collector outputs and additional enable inputs (G1, G2) for bus-oriented control | Better suited for wired-OR bus signaling and gated comparison in shared-resource systems | Choose when interfacing with bidirectional data buses or requiring output enable/disable control |
Compared with SN74LS682N and SN74LS688N, the SN74LS684N uniquely balances full cascading capability with standard push-pull outputs-making it optimal for hierarchical address decoding and multi-stage ALU designs where both expandability and direct TTL fanout are required.
Availability
SN74LS684N is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment refurbishment, and educational lab kits requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74LS684N 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial and automotive qualification.
The SN74LS684N belongs to TI's legacy 74LS logic family, designed specifically for high-reliability, discrete-logic-based digital systems where predictable timing, robust noise margins, and long-term component availability are critical.
FAQ
What is the primary function of the SN74LS684N?
The SN74LS684N is an 8-bit magnitude comparator that determines whether one 8-bit binary number is less than, equal to, or greater than another. It produces three active-low outputs (A<B, A=B, A>B) and supports cascading for multi-byte comparisons. Its design enables deterministic, combinational decision-making in address decoders, ALUs, and bus arbitration logic without internal storage or clocks.
Does the SN74LS684N support cascading with other comparators?
Yes, the SN74LS684N supports hierarchical expansion via three dedicated cascading inputs: IA<B, IA=B, and IA>B. These accept results from a higher-order comparator stage, allowing seamless construction of 16-bit, 24-bit, or wider magnitude comparison systems. This feature distinguishes it from the SN74LS682N and makes the SN74LS684N essential for multi-word address decoding and extended ALU implementations.
What are the supply voltage and operating temperature specifications for the SN74LS684N?
The SN74LS684N operates from 4.75 V to 5.25 V and is rated for 0°C to 70°C ambient temperature. These specifications align with commercial-grade TTL logic standards and ensure reliable performance in office equipment, test instrumentation, and non-military industrial environments. The device does not support extended or military temperature ranges-those require SN54LS684J variants.
Can the SN74LS684N be used as a direct replacement for SN74LS682N?
No, the SN74LS684N is not a direct replacement for SN74LS682N due to functional differences: SN74LS684N includes cascading inputs (pins 18–19), while SN74LS682N omits them and has different pin assignments. Substituting SN74LS684N into an SN74LS682N design may cause incorrect logic behavior unless the unused cascading inputs are properly terminated and the PCB layout accommodates the identical pin count but distinct signal mapping.
What packaging options are available for the SN74LS684N?
The SN74LS684N is offered exclusively in the 20-pin plastic dual in-line package (PDIP-N), with part marking "SN74LS684N" and tube packaging (20 units per tube). Unlike SOIC or SOP variants (e.g., SN74LS684DWR or SN74LS684NSR), the SN74LS684N is through-hole mounted and RoHS-compliant with NiPdAu lead finish, making it suitable for prototyping, repair, and legacy manufacturing processes.
SN74LS684N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Magnitude Comparator
- Number of Bits:
- 8
- Output:
- Active Low
- Output Function:
- A=B, A>B
- Voltage - Supply:
- 4.85V ~ 5.25V
- Current - Output High, Low:
- 400µA, 24mA
- Max Propagation Delay @ V, Max CL:
- 30ns @ 5V, 45pF
- Current - Quiescent (Iq):
- -
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 20-PDIP
- Mounting Type:
- Through Hole
SN74LS684N FAQ
1.How can I place an order for SN74LS684N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS684N 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 SN74LS684N reliable?
The price and inventory of SN74LS684N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS684N is usually 5 days.
3.What payment methods are accepted for SN74LS684N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS684N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS684N?
SN74LS684N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS684N 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 SN74LS684N?
For technical support, including SN74LS684N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS684N requirements.
6.How does Aetrix verify that SN74LS684N is sourced from the original manufacturer or authorized distributors?
All SN74LS684N 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 SN74LS684N meets industry standards.
7.What is the process for return or replacement of SN74LS684N?
All SN74LS684N units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS684N, 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 SN74LS684N part is unused and in its original packaging.
Return procedure for SN74LS684N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74LS684N Tags
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