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Texas Instruments SN74ALS243ANSR
- Part No.:
- SN74ALS243ANSR
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS243ANSR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 14SOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,450
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Product details
Overview
SN74ALS243ANSR from Texas Instruments is a quadruple 2-bit bus transceiver IC designed for asynchronous two-way data communication between parallel buses in TTL-compatible systems. It features dual independent output-enable controls (OEAB and OEBA), supports A↔B bidirectional data flow, latches data when both enables are active, and operates at 4.5–5.5 V over 0°C to 70°C. It is used in legacy industrial control backplanes and vintage computer bus arbitration circuits.
For engineers reviewing the SN74ALS243ANSR datasheet, SN74ALS243ANSR pinout, SN74ALS243ANSR application, or SN74ALS243ANSR equivalent, this device requires attention to its dual-enable timing behavior, 3-state output isolation, pnp-input DC loading reduction, and SO-14 package constraints in board-level integration.
Technical Context
The SN74ALS243ANSR implements a dual-control 3-state transceiver architecture with separate OEAB (A-to-B enable) and OEBA (B-to-A enable) inputs. Its logic allows four distinct functional modes: A→B transmission, B→A transmission, full bus isolation, and simultaneous latch mode where both buses retain identical 4-bit states.
It uses ALS (Advanced Low-Power Schottky) TTL technology with pnp input stages to reduce DC loading on driving sources, and delivers ±12 mA output drive at VOH ≥2.0 V and VOL ≤0.4 V under standard load conditions. Propagation delays range from 4 ns (min) to 11 ns (max) for data paths, and enable/disable times are specified up to 22 ns.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL rails; no regulation required beyond typical decoupling. |
| Operating Temperature | 0°C to 70°C - commercial-grade rating suitable for non-military embedded control environments. |
| Output Drive | IOH = −12 mA, IOL = 24 mA - sufficient to drive multiple TTL loads without external buffers. |
| Propagation Delay | tPLH/tPHL ≤11 ns (max) at CL = 50 pF - enables reliable operation in sub-100 MHz synchronous bus domains. |
| Input Thresholds | VIH = 2.0 V, VIL = 0.8 V - matches standard TTL logic levels; ensures interoperability with 74LS/74ALS families. |
| Enable Timing | tPZL/tPLZ ≤22 ns (max) - defines minimum control pulse width needed to guarantee clean 3-state transitions. |
Pinout & Package
SN74ALS243ANSR is housed in a 14-pin plastic small-outline (SO) package (Package Drawing NS), with 300-mil width and gull-wing leads. Pin 7 is GND, Pin 14 is VCC, and all signal pins are arranged for compact PCB layout in bus interface applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OEAB) | A-to-B Output Enable | Active-low control: enables data flow from A1–A4 to B1–B4 when low; high disables B outputs to high-impedance. |
| 2 (A1) | Bus A Input/Output | Bidirectional I/O port: connects to A-side data bus; driven by A source or reflects B-side state during latch mode. |
| 3 (A2) | Bus A Input/Output | Second bidirectional A-port line; electrically identical to A1 with same timing and drive capability. |
| 4 (A3) | Bus A Input/Output | Third bidirectional A-port line; shares common enable logic and electrical specs with A1–A4. |
| 5 (A4) | Bus A Input/Output | Fourth and final A-port line; completes 4-bit A-bus interface; no internal pull-ups or pull-downs. |
| 6 (GND) | Ground Reference | Primary signal return path; must be low-inductance connection to minimize switching noise coupling. |
| 7 (B1) | Bus B Input/Output | Bidirectional I/O port: connects to B-side data bus; driven by B source or reflects A-side state during latch mode. |
| 8 (B2) | Bus B Input/Output | Second bidirectional B-port line; functionally symmetric to B1 with matched propagation characteristics. |
| 9 (B3) | Bus B Input/Output | Third B-port line; shares same enable structure (OEBA) and electrical specs as B1–B4. |
| 10 (B4) | Bus B Input/Output | Fourth B-port line; completes 4-bit B-bus interface; supports simultaneous latching with A-bus lines. |
| 11 (VCC) | Power Supply | +5 V supply rail; requires local 0.1 µF ceramic decoupling capacitor placed within 5 mm of this pin. |
| 12 (OEBA) | B-to-A Output Enable | Active-low control: enables data flow from B1–B4 to A1–A4 when low; high disables A outputs to high-impedance. |
| 13, 14 | No Internal Connection | NC pins - must remain unconnected; no routing or thermal relief required on PCB. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent output enables | OEAB and OEBA allow asymmetric bus control-e.g., A→B active while B→A isolated-enabling flexible arbitration in multi-master systems. |
| Simultaneous latch mode | When OEAB = OEBA = L, both A and B buses retain identical 4-bit states without external clock or storage elements. |
| pnp input structure | Reduces DC input current to ≤20 µA (IIH) and ≤−0.1 mA (IIL), minimizing loading on upstream TTL or CMOS drivers. |
| ALS TTL compatibility | Meets 74ALS voltage thresholds and timing, ensuring drop-in replacement for SN74ALS240/241/244 in existing designs. |
| 300-mil SO-14 footprint | Matches industry-standard PDIP-14 pad layout with reduced area and improved thermal performance over through-hole packages. |
Applications
| Industrial Backplane Interface | Vintage Computer Bus Arbitration |
|---|---|
|
Use Scenario: Isolating and routing data between CPU and peripheral modules in programmable logic controller (PLC) chassis backplanes. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing shared address/data lines between processor and I/O cards with independent direction control. Use Value: Enables hot-swap-safe isolation via OEAB/OEBA toggling, preventing bus contention during module insertion/removal. |
Use Scenario: Managing data flow between Z80 CPU and memory-mapped peripherals in retro-computing hardware replicas. IC Role / Device Role / Timing Role: Direction-controlled transceiver synchronizing 8-bit data transfers between CPU data bus and peripheral registers. Use Value: Supports cycle-accurate read/write handshaking using OEAB/OEBA as strobe-controlled gate signals. |
| Legacy Test Equipment Data Routing | Embedded System Bus Extension |
|
Use Scenario: Switching measurement data between analog front-end ADCs and digital processing units in discontinued benchtop instruments. IC Role / Device Role / Timing Role: Asynchronous bus coupler enabling reconfigurable signal path selection without FPGA or microcontroller intervention. Use Value: Eliminates need for software-controlled GPIO direction management-hardware-only control reduces latency and firmware complexity. |
Use Scenario: Extending a microcontroller's limited GPIO count by connecting external parallel I/O expanders via shared data bus. IC Role / Device Role / Timing Role: Level-shifting and direction-managed bridge between MCU-native bus and off-chip peripheral interfaces. Use Value: Provides deterministic 4-bit bidirectional throughput with sub-12 ns delay-critical for real-time sensor polling loops. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS240N | Octal inverting buffer with single-direction 3-state control (no B→A path); lacks dual-enable latch mode. | Suitable only for unidirectional bus buffering; cannot replace bidirectional functionality of SN74ALS243ANSR. | Select only if system requires fixed A→B flow and space-constrained octal layout. |
| SN74ALS244N | Octal non-inverting buffer with single-direction 3-state control; identical pinout to SN74ALS240N but non-inverting. | Same unidirectional limitation; no OEBA/OEAB dual control or latch capability. | Prefer when signal polarity preservation is mandatory and bidirectionality is not required. |
Compared with SN74ALS240N and SN74ALS244N, the SN74ALS243ANSR uniquely supports true bidirectional data flow with independent direction control and hardware latch mode-making it irreplaceable in applications requiring dynamic bus arbitration or state retention without clocks.
Availability
SN74ALS243ANSR is available at Aetrix Electronics and suitable for industrial backplane interfaces, vintage computer restoration projects, legacy test equipment repair, and embedded bus extension designs requiring stable component supply across long-lifecycle programs.
Supply support for SN74ALS243ANSR 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 automotive reach.
The SN74ALS243ANSR belongs to TI's legacy 74ALS logic family, engineered for high-speed, low-power TTL-compatible bus interfacing in systems where reliability and backward compatibility outweigh modern integration requirements.
FAQ
What is the operating temperature range for the SN74ALS243ANSR?
The SN74ALS243ANSR is rated for commercial operation from 0°C to 70°C. This range is defined in the recommended operating conditions table of the SDAS069B datasheet and applies specifically to the SN74ALS243A variant in SO-14 (NS) packaging. It does not support extended or military temperature ranges-those require the SN54ALS243A variant in FK or J packages.
Does the SN74ALS243ANSR support true bidirectional data transfer?
Yes, the SN74ALS243ANSR supports true bidirectional data transfer via two independent active-low enables: OEAB controls A→B flow, and OEBA controls B→A flow. When both are low, the device enters latch mode-holding identical 4-bit states on both buses without external clocking. This behavior is confirmed in the FUNCTION TABLE and logic diagram of the SN74ALS243ANSR datasheet.
What package type is used for the SN74ALS243ANSR?
The SN74ALS243ANSR uses a 14-pin plastic small-outline (SO) package with NS drawing designation-commonly referred to as SO-14 or narrow SOIC. This is explicitly listed in TI's Packaging Information addendum, where "SN74ALS243ANSR" maps to "SO" and "NS", distinguishing it from PDIP (N) and ceramic LCCC (FK) variants of the same family.
Can the SN74ALS243ANSR be used as a direct replacement for SN74ALS240N or SN74ALS244N?
No-the SN74ALS243ANSR is not a direct replacement for SN74ALS240N or SN74ALS244N due to fundamental functional differences: those are octal unidirectional buffers with single enable, while the SN74ALS243ANSR is a quadruple bidirectional transceiver with dual enables and latch capability. Pinouts differ, and direction control logic is incompatible.
What is the maximum capacitive load the SN74ALS243ANSR can drive reliably?
The SN74ALS243ANSR is characterized for reliable operation with a 50 pF capacitive load, as specified in the switching characteristics section of the SDAS069B datasheet. Propagation delay (tPLH/tPHL ≤11 ns) and enable timing (tPZL/tPLZ ≤22 ns) are guaranteed under this condition. Driving heavier loads may increase delay and degrade noise margins, requiring empirical validation per application.
SN74ALS243ANSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 14-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 4
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SO
SN74ALS243ANSR FAQ
1.How can I place an order for SN74ALS243ANSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS243ANSR 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 SN74ALS243ANSR reliable?
The price and inventory of SN74ALS243ANSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS243ANSR is usually 5 days.
3.What payment methods are accepted for SN74ALS243ANSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS243ANSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS243ANSR?
SN74ALS243ANSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS243ANSR 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 SN74ALS243ANSR?
For technical support, including SN74ALS243ANSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS243ANSR requirements.
6.How does Aetrix verify that SN74ALS243ANSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS243ANSR 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 SN74ALS243ANSR meets industry standards.
7.What is the process for return or replacement of SN74ALS243ANSR?
All SN74ALS243ANSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS243ANSR, 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 SN74ALS243ANSR part is unused and in its original packaging.
Return procedure for SN74ALS243ANSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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