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Texas Instruments SN74AS298DR
- Part No.:
- SN74AS298DR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
SN74AS298DR.pdf
- Description:
- MUX, AS SERIES, 1-FUNC, TTL
- Quantity:
- Payment:
- Shipping:
Inventory:2,500
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Product details
Overview
SN74AS298DR from Texas Instruments is a quadruple 2-input multiplexer with synchronous storage, functioning as a dual 4-bit register with word-select control. It operates at up to 62 MHz, supports 5-V supply, delivers 20-mA sink output drive, and is characterized for 0°C to 70°C operation. It enables operand/constant selection in arithmetic processors while freeing register files for new data acquisition.
For engineers reviewing the SN74AS298DR datasheet, SN74AS298DR pinout, SN74AS298DR application, or SN74AS298DR equivalent, this page provides verified functional identity, timing-critical setup/hold values (tsu = 13 ns for WS, th = 1 ns), output drive capability (IOL = 20 mA), clock frequency limit (62 MHz), and package-specific terminal mapping for SOIC-16 (D package).
Technical Context
The SN74AS298DR implements two independent 4-bit data paths selectable via the WS input, with synchronous edge-triggered latching on the negative-going CLK transition. Its internal structure combines multiplexing logic and D-type flip-flops in a single 16-pin device, eliminating need for discrete SN74AS157 + SN74AS175A pairing.
It supports universal shift-register configurations - including compound left-right shifts and parallel-load capability - by reconfiguring feedback paths between QA–QD outputs and A1–D2 inputs. Timing is defined relative to CLK↓, with guaranteed tsu(WS) = 13 ns and th(WS) = 1 ns under recommended operating conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures compatibility with standard TTL/AS logic rails and stable operation across industrial voltage tolerances. |
| Max Clock Frequency | 62 MHz - defines maximum synchronous data throughput rate for register updates or shift operations. |
| Output Sink Current | 20 mA - supports direct driving of multiple TTL inputs or moderate fanout without external buffers. |
| Propagation Delay | tPLH = 2–9 ns, tPHL = 1–11 ns - determines worst-case timing margin for downstream logic sampling. |
| Operating Temperature | 0°C to 70°C - specifies commercial-grade ambient range suitable for non-extended-environment computing and control systems. |
| Input Voltage Thresholds | VIH = 2.0 V, VIL = 0.8 V - defines valid logic-high/low recognition levels compatible with AS-family interfacing. |
| Setup Time (WS) | 13 ns before CLK↓ - critical timing constraint for reliable word-select synchronization during high-speed operation. |
Pinout & Package
SN74AS298DR is supplied in a 16-pin SOIC (D) package with 1.27-mm pitch, JEDEC MS-012AC compliant, moisture sensitivity level 1 (260°C peak reflow).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | B2 | Data input B of second 4-bit word - selected when WS = H and latched on CLK↓. |
| 2 | A2 | Data input A of second 4-bit word - forms MSB of selected word when WS = H. |
| 3 | A1 | Data input A of first 4-bit word - forms MSB of selected word when WS = L. |
| 4 | B1 | Data input B of first 4-bit word - selected when WS = L and latched on CLK↓. |
| 5 | C2 | Data input C of second 4-bit word - contributes to mid-byte selection under WS = H. |
| 6 | D2 | Data input D of second 4-bit word - forms LSB of selected word when WS = H. |
| 7 | D1 | Data input D of first 4-bit word - forms LSB of selected word when WS = L. |
| 8 | GND | Ground reference - required return path for all internal logic and output current sinks. |
| 9 | VCC | Positive supply - powers all internal gates, flip-flops, and output drivers at 4.5–5.5 V. |
| 10 | QA | Output A of stored 4-bit word - reflects latched A1/A2 value depending on WS state. |
| 11 | QB | Output B of stored 4-bit word - synchronized to CLK↓ and controlled by WS selection. |
| 12 | QC | Output C of stored 4-bit word - provides third bit of registered output with full setup/hold compliance. |
| 13 | QD | Output D of stored 4-bit word - LSB output, capable of sourcing/sinking specified IOL/IOH currents. |
| 14 | CLK | Clock input - negative-edge-triggered; all register updates occur on CLK↓ transition. |
| 15 | WS | Word Select - selects A1/B1/C1/D1 (WS = L) or A2/B2/C2/D2 (WS = H) for latching. |
| 16 | C1 | Data input C of first 4-bit word - contributes to mid-byte selection under WS = L. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 4-bit register + mux integration | Replaces discrete SN74AS157 (mux) and SN74AS175A (quad D-FF) - reduces board area and interconnect complexity. |
| Negative-edge clocking | Ensures deterministic register update timing aligned to CLK↓, simplifying synchronous system design. |
| High-speed operation | 62-MHz max clock rate enables use in fast arithmetic logic units and real-time data routing applications. |
| Robust output drive | 20-mA sink capability allows direct interface to multiple TTL loads or legacy bus structures without buffering. |
| Parallel load + shift flexibility | Supports both immediate parallel loading and configurable shift patterns (left/right/compound) via external feedback. |
Applications
| Arithmetic Processor Operand Selection | BCD Digit Shift Register |
|---|---|
Use Scenario: Arithmetic processor requires alternating access to two 4-bit operand sources (e.g., ALU inputs vs. constant ROM) without stalling register file reads. IC Role / Device Role / Timing Role: SN74AS298DR acts as a synchronous word-select register, gating either operand set into pipeline registers on each CLK↓. Use Value: Frees processor register files for concurrent data acquisition while maintaining deterministic 62-MHz operand switching latency. | Use Scenario: BCD-based calculator or display controller must shift entire 4-bit digits left/right in one clock cycle for decimal alignment or scrolling. IC Role / Device Role / Timing Role: SN74AS298DR functions as a universal 4-bit shift register with parallel-load capability, using QA–QD feedback to A1–D2. Use Value: Enables single-cycle digit movement and atomic parallel reload - critical for responsive numeric display updates and keyboard input handling. |
| ALU-Controlled Multi-Place Shifter | Register File Exchange Interface |
Use Scenario: Hardware multiplier/divider unit needs dynamic shift distance selection (1-place vs. 2-place) based on ALU status flags. IC Role / Device Role / Timing Role: SN74AS298DR serves as a programmable shifter stage where WS controls shift magnitude, and CLK synchronizes ALU output capture. Use Value: Achieves variable-shift functionality without microcode or additional control logic - reducing cycle count per multiply/divide operation. | Use Scenario: Dual-register bank system (e.g., context-switching in early microcontrollers) requires atomic exchange of 4-bit register contents between banks. IC Role / Device Role / Timing Role: SN74AS298DR implements bidirectional register coupling: Bank A outputs feed A1–D1, Bank B feeds A2–D2, and WS toggles direction. Use Value: Enables zero-cycle register swap via synchronized WS toggle and CLK pulse - improving interrupt latency and task-switch efficiency. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multiplexer-with-storage applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS157D + SN74AS175AD | Two separate ICs: quad 2-input mux + quad D-type flip-flop; requires additional PCB routing and timing coordination. | Lacks integrated word-select latch; cannot achieve same setup/hold timing integrity as monolithic SN74AS298DR. | Choose only if board layout already accommodates dual-package footprint or legacy design reuse is mandatory. |
| SN74F299N | 8-bit universal shift register with 3-state outputs; no built-in dual-word mux function; different pinout and control logic (S0/S1 instead of WS). | Requires external logic to emulate word-select behavior; lacks native 4-bit dual-source capability. | Select when 8-bit width and 3-state bus driving are primary requirements - not for direct SN74AS298DR replacement. |
Compared with SN74AS157D+SN74AS175AD, the SN74AS298DR eliminates inter-device skew and reduces component count; versus SN74F299N, it offers dedicated 4-bit dual-source selection with tighter timing control but no 3-state or 8-bit support.
Availability
SN74AS298DR is available at Aetrix Electronics and suitable for arithmetic logic units, BCD display controllers, hardware multipliers, and register-exchange subsystems requiring stable component supply and long-term obsolescence management.
Supply support for SN74AS298DR 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 technologies with broad industrial and computing heritage.
The SN74AS298DR belongs to the 74AS advanced Schottky logic family, designed for high-speed digital systems requiring sub-10-ns propagation delays and robust noise immunity in commercial-temperature environments.
FAQ
What is the maximum clock frequency supported by the SN74AS298DR?
The SN74AS298DR supports a maximum clock frequency of 62 MHz under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C). This rating is validated by timing measurements with CL = 50 pF and defines the upper limit for reliable negative-edge-triggered register updates. Exceeding this frequency risks setup/hold violations, particularly for the WS input (tsu = 13 ns, th = 1 ns), and may result in metastability or incorrect word selection in the SN74AS298DR.
Does the SN74AS298DR support 3-state outputs?
No, the SN74AS298DR does not feature 3-state outputs. Its QA, QB, QC, and QD terminals are push-pull totem-pole outputs with specified IOH = −2 mA and IOL = 20 mA drive capability. Unlike devices such as SN74AS299, the SN74AS298DR lacks output-enable (OE) control or high-impedance states. System-level bus sharing must therefore be implemented externally using additional logic or buffer ICs when using the SN74AS298DR.
How does the word-select (WS) input determine data routing in the SN74AS298DR?
The WS input directly controls source selection: when WS is low, the A1/B1/C1/D1 inputs are routed to QA/QB/QC/QD on the next CLK↓; when WS is high, A2/B2/C2/D2 are selected instead. This action occurs synchronously on the negative clock edge - no latching occurs at other times. The SN74AS298DR retains prior output states (QA0–QD0) while WS is held high or low between clocks, making WS a static control signal rather than a sampled input. This behavior is confirmed in the function table and logic diagram of the SN74AS298DR datasheet.
Can the SN74AS298DR be used as a universal shift register?
Yes, the SN74AS298DR can implement universal shift register functionality - including left, right, and compound shifts - by feeding QA–QD outputs back to appropriate A1–D2 inputs and controlling WS to select feedback paths. Application examples in the datasheet demonstrate BCD digit shifting and 1-/2-place ALU-controlled shifts. However, unlike dedicated shift registers, the SN74AS298DR requires external wiring for feedback and does not include built-in serial-in/serial-out capability. Its utility as a shift register derives entirely from its dual-source mux + storage architecture, not from native shift logic.
What package type is used for the SN74AS298DR, and is it RoHS-compliant?
The SN74AS298DR uses a 16-pin SOIC (D) package with 1.27-mm lead pitch, conforming to JEDEC MS-012AC. Per TI's packaging addendum, it is manufactured with green (RoHS & no Sb/Br) eco plan, CU NIPDAU finish, and MSL Level-1 rating (unlimited floor life at ≤30°C/60% RH). This confirms full RoHS compliance and suitability for lead-free reflow processes. The SN74AS298DR is distinct from the PDIP (N) variant, which uses Pb-Free (RoHS) finish but lacks MSL classification due to through-hole construction.
SN74AS298DR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- -
- Circuit:
- -
- Independent Circuits:
- -
- Current - Output High, Low:
- -
- Voltage Supply Source:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN74AS298DR FAQ
1.How can I place an order for SN74AS298DR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS298DR 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 SN74AS298DR reliable?
The price and inventory of SN74AS298DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS298DR is usually 5 days.
3.What payment methods are accepted for SN74AS298DR?
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4.How is shipping managed for SN74AS298DR?
SN74AS298DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS298DR 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 SN74AS298DR?
For technical support, including SN74AS298DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS298DR requirements.
6.How does Aetrix verify that SN74AS298DR is sourced from the original manufacturer or authorized distributors?
All SN74AS298DR 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 SN74AS298DR meets industry standards.
7.What is the process for return or replacement of SN74AS298DR?
All SN74AS298DR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS298DR, 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 SN74AS298DR part is unused and in its original packaging.
Return procedure for SN74AS298DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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