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Texas Instruments SN74AS298AD
- Part No.:
- SN74AS298AD
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74AS298AD.pdf
- Description:
- IC MULTIPLEXER 4 X 2:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,600
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Product details
Overview
SN74AS298AD from Texas Instruments is a quadruple 2-input multiplexer with synchronous storage, functioning as a dual 4-bit selectable register with clocked output latching. It supports two independent 4-bit data sources (A1–D1 and A2–D2), selects between them via WS input, and latches the chosen word on the negative edge of CLK. It operates at up to 62 MHz across 0°C to 70°C and is used in arithmetic processor operand routing and BCD shift register implementation.
For engineers reviewing the SN74AS298AD datasheet, SN74AS298AD pinout, SN74AS298AD application, or SN74AS298AD equivalent, this device is critical for high-speed register exchange, parallel-load shift registers, and ALU-adjacent data path control where deterministic timing and dual-source selection are required.
Technical Context
The SN74AS298AD integrates multiplexing and edge-triggered D-type flip-flop functionality in a single 16-pin IC: it routes one of two 4-bit words to four independent storage elements, each clocked synchronously on CLK's falling edge. Its WS-controlled selection enables dynamic source switching without intermediate latching stages.
It uses bipolar Advanced Schottky (AS) technology, delivering 62 MHz maximum clock frequency, 2 ns typical tPLH, and 1 ns typical tPHL propagation delays. Input thresholds are VIH ≥ 2 V and VIL ≤ 0.8 V at VCC = 5 V, with guaranteed 20 mA sink and −2 mA source drive capability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | Advanced Schottky TTL (AS), compatible with 5-V TTL systems and offering higher speed than LS/ALS variants. |
| Max Clock Frequency | 62 MHz - enables sub-16 ns cycle time for real-time register update in arithmetic pipelines. |
| Propagation Delay (tPLH/tPHL) | 2 ns / 1 ns typical - ensures tight timing margins in multi-stage synchronous data paths. |
| Output Drive (IOL/IOH) | 20 mA sink / −2 mA source - sufficient to drive multiple TTL inputs or small capacitive loads directly. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded control and test equipment environments. |
| Supply Voltage Range | 4.5 V to 5.5 V - requires stable 5-V rail; not tolerant of undervoltage or overvoltage operation. |
| Input Thresholds (VIH/VIL) | ≥2.0 V / ≤0.8 V - provides noise margin >0.4 V under nominal VCC = 5 V conditions. |
Pinout & Package
SN74AS298AD is housed in a 16-pin SOIC (D) package, 3.94 mm wide, with 1.27 mm pitch, RoHS-compliant NiPdAu lead finish, and MSL Level-1 rating for unlimited reflow exposure.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | B2 | Bit-2 input of second 4-bit source; routed to QB when WS = H and CLK↓ occurs. |
| 2 | A2 | Bit-1 input of second 4-bit source; routed to QA when WS = H and CLK↓ occurs. |
| 3 | A1 | Bit-1 input of first 4-bit source; routed to QA when WS = L and CLK↓ occurs. |
| 4 | B1 | Bit-2 input of first 4-bit source; routed to QB when WS = L and CLK↓ occurs. |
| 5 | C2 | Bit-3 input of second 4-bit source; routed to QC when WS = H and CLK↓ occurs. |
| 6 | D2 | Bit-4 input of second 4-bit source; routed to QD when WS = H and CLK↓ occurs. |
| 7 | D1 | Bit-4 input of first 4-bit source; routed to QD when WS = L and CLK↓ occurs. |
| 8 | GND | Power ground reference for all internal logic and output drivers. |
| 9 | VCC | +5 V supply input; must be decoupled locally due to AS family's high transient current demand. |
| 10 | QA | Registered output for bit-1; holds latched value until next CLK↓ event. |
| 11 | QB | Registered output for bit-2; maintains state independently of other outputs. |
| 12 | QD | Registered output for bit-4; electrically identical to QA/QB/QC in drive and timing. |
| 13 | C1 | Bit-3 input of first 4-bit source; routed to QC when WS = L and CLK↓ occurs. |
| 14 | WS | Word-select control: L selects A1–D1, H selects A2–D2; requires 13 ns setup before CLK↓. |
| 15 | CLK | Clock input triggering latching on negative edge; minimum pulse width 8 ns high/low. |
| 16 | QC | Registered output for bit-3; synchronized to same CLK edge as QA/QB/QD. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 4-bit source selection with synchronous latch | Eliminates need for separate multiplexer + register ICs (e.g., SN74AS157 + SN74AS175A), reducing board area and interconnect delay. |
| Negative-edge clocked storage | Enables precise alignment with system clocks that use falling-edge sampling, avoiding metastability in pipeline stages. |
| AS-family speed-performance | Delivers 62 MHz operation and sub-3 ns propagation-critical for arithmetic logic unit (ALU) operand staging in 1980s–90s processors. |
| Parallel load + shift register capability | Supports BCD digit shifting and 1-/2-place binary shifts via WS control, enabling compact multiplier/divider microarchitectures. |
| Commercial temperature range (0°C to 70°C) | Validated for use in desktop computers, test instrumentation, and industrial controllers where ambient thermal management is controlled. |
Applications
| Arithmetic Processor Operand Routing | BCD Digit Shift Register |
|---|---|
|
Use Scenario: Routing operands and constants from dual register files into an ALU during instruction execution cycles. IC Role / Device Role / Timing Role: SN74AS298AD acts as a synchronous operand selector and latch, feeding pre-aligned 4-bit data to ALU inputs on each CLK↓. Use Value: Frees up general-purpose registers by enabling external constant storage and dynamic source switching without software overhead. |
Use Scenario: Shifting entire 4-bit BCD digits left/right in a calculator or digital counter ASIC. IC Role / Device Role / Timing Role: SN74AS298AD implements a universal 4-bit shift register where WS controls direction and CLK triggers atomic digit movement. Use Value: Achieves full-digit shift in one clock cycle-unlike serial shifters-improving throughput in decimal arithmetic units. |
| ALU-Accelerated Multiplier Core | Register File Parallel Exchange |
|
Use Scenario: Supporting iterative multiplication by shifting partial products while retaining accumulator contents. IC Role / Device Role / Timing Role: SN74AS298AD serves as a programmable shifter: WS = L shifts 1 place (ALU output → register), WS = H shifts 2 places (register → register). Use Value: Reduces microcode steps per multiply iteration, cutting latency in fixed-point math coprocessors. |
Use Scenario: Swapping contents between two 4-bit register banks in a microcontroller datapath. IC Role / Device Role / Timing Role: SN74AS298AD functions as a bidirectional register coupler: WS toggles direction, CLK executes atomic exchange. Use Value: Enables zero-cycle register swap for context switching or pipeline forwarding without additional control logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 4-bit multiplexed register applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS298AN | Same logic function and timing, but in 16-pin PDIP (N) package with 0.3″ width and through-hole mounting. | Used where manual prototyping, socket-based testing, or legacy PCB layouts require DIP footprint. | Select SN74AS298AN for breadboarding or replacement in existing DIP-based systems; SN74AS298AD for surface-mount production. |
| SN74F298N | Fast TTL variant with lower max frequency (35 MHz), higher power (ICCL ≈ 50 mA), and looser timing margins (tPLH up to 12 ns). | Suitable for cost-sensitive or thermally constrained designs where 62 MHz is unnecessary. | Choose SN74F298N only if system clock <30 MHz and board-level heat dissipation limits preclude AS-family current draw. |
Compared with SN74AS298AN and SN74F298N, the SN74AS298AD delivers highest speed and lowest propagation skew in a space-efficient SOIC package, making it optimal for high-density, high-throughput digital control logic where timing precision is critical.
Availability
SN74AS298AD is available at Aetrix Electronics and suitable for arithmetic processor design, BCD-based instrumentation, register file management, and ALU-adjacent datapath control requiring stable component supply and long-term commercial availability.
Supply support for SN74AS298AD 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 leader founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial and computing heritage.
The SN74AS298AD belongs to TI's 74AS advanced Schottky TTL logic family, engineered for high-speed digital control in 1980s–90s computing, test equipment, and industrial controllers where deterministic timing and robust noise immunity were essential.
FAQ
What is the primary function of the SN74AS298AD?
The SN74AS298AD is a quadruple 2-input multiplexer with synchronous storage: it selects one of two 4-bit data words (A1–D1 or A2–D2) based on the WS input and latches the selected word to QA–QD outputs on the falling edge of CLK. Its core function is dual-source routing with edge-triggered register behavior, not simple signal switching.
Does the SN74AS298AD support 3-state outputs?
No, the SN74AS298AD does not have 3-state outputs. All outputs (QA–QD) are push-pull TTL-compatible and always driven-either high or low-when enabled. There is no output enable (OE) pin or high-impedance mode; bus sharing requires external gating or buffer isolation.
What is the minimum required setup time for the WS input relative to CLK↓?
The SN74AS298AD requires a minimum WS setup time (tsu) of 13 ns before the falling edge of CLK, as specified in the "timing requirements" table of the SDAS219B datasheet. Violating this window risks metastability or incorrect word selection on that clock cycle.
Can the SN74AS298AD operate at 3.3 V?
No, the SN74AS298AD is not rated for 3.3 V operation. Its recommended supply voltage is 4.5 V to 5.5 V, and absolute maximum VCC is 7 V. Operation below 4.5 V may cause timing violations, reduced noise margin, or functional failure; it is incompatible with modern 3.3 V logic families without level translation.
How does the SN74AS298AD differ from the SN74AS157 + SN74AS175A combination?
The SN74AS298AD integrates the functionality of SN74AS157 (quad 2-input mux) and SN74AS175A (quad D-type flip-flop) into one 16-pin package, eliminating inter-chip routing delays, reducing PCB area, and guaranteeing matched propagation characteristics. Unlike discrete pairing, SN74AS298AD ensures simultaneous latching of all four bits on one CLK edge.
SN74AS298AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- Multiplexer
- Circuit:
- 4 x 2:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 2mA, 20mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74AS298AD FAQ
1.How can I place an order for SN74AS298AD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS298AD 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 SN74AS298AD reliable?
The price and inventory of SN74AS298AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS298AD is usually 5 days.
3.What payment methods are accepted for SN74AS298AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS298AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS298AD?
SN74AS298AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS298AD 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 SN74AS298AD?
For technical support, including SN74AS298AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS298AD requirements.
6.How does Aetrix verify that SN74AS298AD is sourced from the original manufacturer or authorized distributors?
All SN74AS298AD 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 SN74AS298AD meets industry standards.
7.What is the process for return or replacement of SN74AS298AD?
All SN74AS298AD units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS298AD, 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 SN74AS298AD part is unused and in its original packaging.
Return procedure for SN74AS298AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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