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Texas Instruments SN74AS885NT3
- Part No.:
- SN74AS885NT3
- Manufacturer:
- Texas Instruments
- Category:
- Comparators
- Package:
- -
- Datasheet:
-
SN74AS885NT3.pdf
- Description:
- MAGNITUDE COMPARATOR
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Product details
Overview
SN74AS885NT3 from Texas Instruments is an 8-bit magnitude comparator IC with latched P-input port, dual-mode (logical/arithmetic) comparison, and cascading capability for n-bit expansion. It operates from 4.5 V to 5.5 V, delivers propagation delays as low as 1 ns (tPHL/tPLH), and supports TTL-compatible input/output levels. It is used in high-speed digital systems requiring real-time binary word comparison - such as address decoding in legacy microprocessor buses or arithmetic logic unit (ALU) support circuits.
For engineers reviewing the SN74AS885NT3 datasheet, SN74AS885NT3 pinout, SN74AS885NT3 application, or SN74AS885NT3 equivalent, key selection criteria include its latch-enable (PLE) transparency timing, P > QOUT/P < QOUT cascade delay (≤10 ns), dual L/A mode selection, and compatibility with standard 24-pin PDIP layouts in industrial control and test equipment designs.
Technical Context
The SN74AS885NT3 implements a fully decoded 8-bit magnitude comparison using advanced Schottky TTL (AS) technology, with separate P > QOUT and P < QOUT outputs that drive subsequent stages with only two-gate-level delay. Its L/A pin selects between logical (unsigned) and arithmetic (two's complement) comparison modes, enabling flexible use in both data-path and signed ALU contexts.
It features a transparent latch on the P-input port controlled by PLE: P-data is latched on PLE low, allowing temporary storage without external registers. All P, Q, and PLE inputs use pnp input transistors, limiting low-level input current to –0.25 mA and reducing dc loading on driving sources - critical for fanout-limited TTL bus designs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL power rails; no external regulation required. |
| Propagation Delay (tPLH/tPHL) | 1 ns (min), 13 ns (max) - enables sub-100 MHz system clock domain interfacing in legacy high-speed logic. |
| Output Drive (IOL/IOH) | 20 mA sink / –2 mA source - sufficient to directly drive multiple 74AS inputs or small LED indicators. |
| Input Current (IIL/IIH) | –1 mA (low), 20 µA (high) - minimizes loading on upstream TTL or CMOS drivers in mixed-logic systems. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded instrumentation and industrial control panels. |
| Cascade Delay Penalty | ≤10 ns per stage - allows reliable 32-bit+ comparisons with predictable timing budgeting. |
| Logic Family | Advanced Schottky TTL (AS) - provides ~35% faster ac performance vs. standard Schottky TTL while maintaining pinout and voltage compatibility. |
Pinout & Package
SN74AS885NT3 uses a 24-pin plastic dual-in-line package (PDIP), 300-mil width, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is marked by notch or dot; pin numbering follows counterclockwise convention from top-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | L/A | Mode select: High = logical (unsigned) comparison; Low = arithmetic (two's complement) comparison. |
| 2 | P < QIN | Cascade input: accepts P < Q result from less-significant stage during multi-word comparison. |
| 3 | P > QIN | Cascade input: accepts P > Q result from less-significant stage during multi-word comparison. |
| 4–11 | Q0–Q7 | 8-bit non-latched operand input port (Q-word); asynchronous comparison input. |
| 12 | GND | Ground reference for all internal logic and output drivers. |
| 13 | P > QOUT | Primary output: active-high when P > Q (mode-dependent); drives next-stage P > QIN. |
| 14 | P < QOUT | Primary output: active-high when P < Q (mode-dependent); drives next-stage P < QIN. |
| 15–22 | P0–P7 | 8-bit latched operand input port (P-word); data held stable after PLE transition. |
| 23 | PLE | Port latch enable: high = transparent (P-data passes through); low = latched (P-data frozen). |
| 24 | VCC | +5 V supply input; decoupling capacitor recommended at pin for noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Latchable P-input port | Enables synchronous capture of P-word independent of Q-word arrival, simplifying timing in pipelined ALUs. |
| Dual comparison mode (L/A) | Single-pin selection between unsigned (address range check) and signed (arithmetic overflow detection) operation. |
| Cascadable architecture | Two dedicated cascade I/Os (P>QIN/P<QIN → P>QOUT/P<QOUT) allow bit-width expansion to n bits with fixed 2-gate delay per stage. |
| pnp input structure | Reduces low-level input current to –0.25 mA, enabling direct interface with 74LS/74ALS without pull-up resistors. |
| AS-family performance | ~35% faster switching than standard Schottky TTL while consuming 10% less power for equivalent 8-bit function. |
Applications
| Address Range Decoder | ALU Auxiliary Comparator |
|---|---|
|
Use Scenario: Decoding memory-mapped I/O or peripheral address ranges in 8080/Z80-based systems where overlapping or adjacent regions must be distinguished. IC Role / Device Role / Timing Role: SN74AS885NT3 compares CPU address bus (Q) against fixed base/mask register (P) to assert chip-select signals with minimal latency. Use Value: Sub-15 ns propagation ensures no wait-state insertion in 4–6 MHz bus cycles; L/A pin configures for unsigned address space. |
Use Scenario: Supporting signed arithmetic operations in discrete-logic ALUs by detecting overflow or sign mismatch during addition/subtraction. IC Role / Device Role / Timing Role: SN74AS885NT3 receives operands from accumulator and register file, configured in arithmetic mode (L/A = low) to evaluate two's complement inequality. Use Value: Direct P > QOUT/P < QOUT outputs feed status logic without combinational glue, reducing critical path delay by ≥2 gates. |
| Test Equipment Word Comparator | Digital Pattern Generator Comparator |
|
Use Scenario: Real-time validation of stimulus-response sequences in automated test fixtures verifying 8-bit microcontroller firmware behavior. IC Role / Device Role / Timing Role: SN74AS885NT3 compares expected output vector (P, latched via PLE) against actual DUT output (Q) on each clock edge. Use Value: PLE-controlled latching synchronizes comparison to test clock; 1 ns min delay enables sampling at ≥80 MHz effective rate. |
Use Scenario: Generating conditional triggers in digital pattern generators when a generated sequence matches or exceeds a threshold value. IC Role / Device Role / Timing Role: SN74AS885NT3 monitors counter output (Q) against programmable limit (P) and asserts trigger when P ≤ Q, with L/A selecting unsigned threshold mode. Use Value: Cascadable design allows multi-threshold triggering (e.g., 16-bit window match) using two SN74AS885NT3 devices with <10 ns inter-stage penalty. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-bit magnitude comparison applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS885DW | Same die, SOIC-24 package; RoHS-compliant; MSL Level-1; no lead finish restrictions. | Preferred for surface-mount production; requires PCB redesign but offers better thermal dissipation and board density. | Select SN74AS885DW for new SMT designs; SN74AS885NT3 remains viable for through-hole repair or legacy rework. |
| SN74F885N | Fast TTL variant: higher ICC (250 mA), slower max delay (20 ns), no PLE latch, no L/A mode - logic-only comparison. | Suitable only for static unsigned comparison where latching and arithmetic mode are unnecessary. | Choose SN74F885N only if cost sensitivity outweighs speed/latch requirements and design can tolerate missing features. |
Compared with SN74AS885DW, SN74AS885NT3 offers identical functionality in through-hole form but lacks RoHS compliance and modern moisture sensitivity handling; compared with SN74F885N, SN74AS885NT3 adds critical latching and dual-mode capability at higher speed and lower power, justifying its use in timing-critical or flexible-logic applications.
Availability
SN74AS885NT3 is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment refurbishment, and microprocessor bus interface designs requiring stable component supply across extended procurement cycles.
Supply support for SN74AS885NT3 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 innovator founded in 1930, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74AS885NT3 belongs to TI's legacy Advanced Schottky TTL logic family, designed specifically for high-speed, low-power digital systems requiring robust fanout, noise immunity, and seamless integration with earlier 74xx-series components.
FAQ
What is the operating temperature range for SN74AS885NT3?
The SN74AS885NT3 is characterized for commercial operation from 0°C to 70°C. This range aligns with standard industrial ambient conditions and supports use in enclosed control cabinets or benchtop instrumentation without forced cooling. It does not meet extended or military temperature specifications - those require the SN54AS885 variant in JT or FK packages.
Does SN74AS885NT3 support arithmetic (two's complement) comparison?
Yes, SN74AS885NT3 supports arithmetic comparison via the L/A pin: when pulled low, it interprets P and Q as two's complement numbers and evaluates relative magnitude accordingly. This enables signed overflow detection and conditional branching in discrete-logic ALUs - a capability absent in basic comparators like SN74F885N.
How does the PLE pin function in SN74AS885NT3?
The PLE (P Latch Enable) pin controls transparency of the P-input port: when high, P0–P7 pass through to internal logic; when low, the last stable values are latched and held regardless of further P-input changes. This allows SN74AS885NT3 to compare a static reference (P) against a dynamic bus (Q), essential for address decode and pattern matching.
Can SN74AS885NT3 be cascaded for more than 8 bits?
Yes, SN74AS885NT3 is explicitly designed for cascading: the P > QOUT and P < QOUT outputs connect directly to P > QIN and P < QIN inputs of another SN74AS885NT3 handling more-significant bits. Each stage adds only two gate delays, enabling reliable 16-, 24-, or 32-bit comparisons with predictable timing - verified in TI's Application Information Figures 1 and 2.
What package type is SN74AS885NT3 supplied in?
SN74AS885NT3 is supplied in a 24-pin plastic dual-in-line package (PDIP), designated NT in TI's packaging nomenclature. It features 300-mil width, through-hole leads, and standard 0.1-inch pin spacing - compatible with legacy prototyping boards, socketed test fixtures, and manual assembly workflows.
SN74AS885NT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- -
- Number of Bits:
- -
- Output:
- -
- Output Function:
- -
- Voltage - Supply:
- -
- Current - Output High, Low:
- -
- Max Propagation Delay @ V, Max CL:
- -
- Current - Quiescent (Iq):
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- -
- Mounting Type:
- -
SN74AS885NT3 FAQ
1.How can I place an order for SN74AS885NT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS885NT3 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 SN74AS885NT3 reliable?
The price and inventory of SN74AS885NT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS885NT3 is usually 5 days.
3.What payment methods are accepted for SN74AS885NT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS885NT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS885NT3?
SN74AS885NT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS885NT3 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 SN74AS885NT3?
For technical support, including SN74AS885NT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS885NT3 requirements.
6.How does Aetrix verify that SN74AS885NT3 is sourced from the original manufacturer or authorized distributors?
All SN74AS885NT3 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 SN74AS885NT3 meets industry standards.
7.What is the process for return or replacement of SN74AS885NT3?
All SN74AS885NT3 units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS885NT3, 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 SN74AS885NT3 part is unused and in its original packaging.
Return procedure for SN74AS885NT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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