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Texas Instruments SN74LS243D
- Part No.:
- SN74LS243D
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS243D.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,358
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Product details
Overview
SN74LS243D from Texas Instruments is a quadruple bus transceiver IC designed for asynchronous two-way data communication between parallel buses in TTL-level systems. It features dual-directional data flow (A↔B), PNP input structure reducing DC loading, 400 mV typical input hysteresis for noise immunity, and operates across 0°C to 70°C. It drives terminated lines down to 133 Ω and supports latch mode (A = B) and isolation states.
For engineers reviewing the SN74LS243D datasheet, SN74LS243D pinout, SN74LS243D application, or SN74LS243D equivalent, key selection considerations include bidirectional bus isolation timing (tPLH/tPHL ≤ 18 ns), output drive capability (IOL = 24 mA), input hysteresis for noisy environments, and SOIC-14 package compatibility with legacy TTL board layouts.
Technical Context
The SN74LS243D implements four independent bidirectional transceivers, each controlled by separate GAB (A-to-B enable) and GBA (B-to-A enable) inputs. Its PNP-input architecture lowers input current draw and improves fan-out in dense TTL bus systems.
Each transceiver supports three functional states per direction: active transmission, high-impedance (Z) output when disabled, and latched state where A and B buses mirror (A = B). Switching performance is specified at VCC = 5 V, RL = 667 Ω, CL = 45 pF, with tPZL ≤ 30 ns and tPLZ ≤ 20 ns ensuring reliable bus turnaround timing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.75 V to 5.25 V - Ensures stable operation within standard TTL supply tolerance without regulation overhead. |
| IOH / IOL | –15 mA / 24 mA - Sustains robust drive into 133 Ω terminated lines while meeting LS-TTL voltage thresholds. |
| Input Hysteresis | Typ. 400 mV - Increases noise margin on shared bus lines subject to crosstalk or EMI in industrial backplanes. |
| tPLH / tPHL | 12 ns / 18 ns max - Enables reliable 25+ MHz bus handshaking in synchronous peripheral interfaces. |
| VIH / VIL | 2.0 V / 0.8 V - Fully compatible with standard 74LS family logic thresholds for seamless integration. |
| ICC (active) | 32–54 mA - Predictable power budget per device for multi-transceiver bus repeater designs. |
Pinout & Package
SN74LS243D is housed in a 14-pin SOIC (Small Outline Integrated Circuit) package, 3.9 mm wide, 8.65 mm long, 1.75 mm max height, RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | GAB | Active-low A-to-B bus enable - When low, enables data flow from A1–A4 to B1–B4. |
| 2–5 | A1–A4 | Bus A data inputs/outputs - Bidirectional I/O pins connected to source bus. |
| 6 | GND | Ground reference - Required return path for all internal logic and output drivers. |
| 7–10 | B1–B4 | Bus B data inputs/outputs - Bidirectional I/O pins connected to destination bus. |
| 11 | GBA | Active-low B-to-A bus enable - When low, enables data flow from B1–B4 to A1–A4. |
| 12–13 | NC | No connect - Internally unconnected pins; must remain floating or grounded per layout best practice. |
| 14 | VCC | Positive supply - Powers all internal logic and output stages at nominal 5 V. |
Key Features
| Feature | Design Value |
|---|---|
| Quadruple bidirectional transceivers | Four independent A↔B channels allow simultaneous multi-line bus bridging without external control logic. |
| PNP input structure | Reduces input current to ≤ –0.2 mA, enabling higher fan-out (up to 20 LS-TTL loads) per input. |
| Input hysteresis (400 mV typ.) | Suppresses false triggering on slow-rising or noisy bus signals, critical in backplane or cable-driven applications. |
| Latch mode (GAB = H, GBA = H) | Forces A and B buses into identical logic states (A = B), useful for bus initialization or diagnostic mirroring. |
| SOIC-14 package | Surface-mount footprint compatible with automated assembly and legacy through-hole board redesigns using adapter footprints. |
Applications
| Industrial Backplane Interface | Legacy System Bus Repeater |
|---|---|
|
Use Scenario: Interfacing isolated PLC I/O modules to a central controller bus over 20 cm PCB traces with shared ground noise. IC Role / Device Role / Timing Role: Bidirectional bus transceiver providing signal integrity isolation and level-consistent data transfer between subsystems. Use Value: Input hysteresis rejects common-mode noise; 24 mA drive ensures clean edges into 133 Ω termination, preventing reflections on long traces. |
Use Scenario: Extending a 74LS-based CPU address/data bus across two PCBs via ribbon cable with impedance mismatch. IC Role / Device Role / Timing Role: Active bus repeater regenerating TTL waveforms and managing direction control for read/write cycles. Use Value: Sub-20 ns propagation delay preserves setup/hold timing margins; SOIC-14 allows compact placement near connectors. |
| Test Equipment Bus Coupler | Embedded Diagnostic Bridge |
|
Use Scenario: Connecting DUT (device under test) and ATE (automatic test equipment) buses with independent enable control per channel. IC Role / Device Role / Timing Role: Isolatable bidirectional coupler enabling selective bus access during functional testing sequences. Use Value: Independent GAB/GBA pins permit per-channel direction gating; NC pins simplify routing in dense test head layouts. |
Use Scenario: Enabling firmware-controlled bidirectional communication between microcontroller peripherals and external memory-mapped devices. IC Role / Device Role / Timing Role: Configurable bus interface supporting both memory read (B→A) and write (A→B) operations under software control. Use Value: Latch mode (A = B) simplifies bus initialization; 0°C to 70°C rating matches industrial MCU operating range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS244N | Octal non-inverting buffer (unidirectional only); no B-to-A path or GBA control. | Suitable only for one-way bus extension; lacks bidirectional arbitration capability. | Select when direction is fixed and higher channel count (8 vs 4) is needed without reverse flow. |
| SN74LS245N | Octal bidirectional transceiver with single direction-control pin (DIR) and output-enable (OE). | Uses shared DIR signal instead of independent GAB/GBA; less granular per-channel control. | Prefer for simpler control logic where all 8 lines switch direction simultaneously, not independently. |
Compared with SN74LS244N and SN74LS245N, the SN74LS243D uniquely provides four independently enabled bidirectional channels-enabling selective A↔B arbitration per line pair-making it optimal for partial-bus isolation, mixed-direction protocols, and diagnostic bus mirroring not supported by octal alternatives.
Availability
SN74LS243D is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus repeaters, test equipment couplers, and embedded diagnostic bridges requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS243D 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 delivering analog, embedded processing, and logic solutions since 1930, with deep heritage in TTL and bipolar logic families.
The SN74LS243D belongs to TI's 74LS logic product line, engineered specifically for reliable, noise-immune bus interfacing in industrial control, instrumentation, and retro-computing systems operating at 5 V.
FAQ
What is the operating temperature range for SN74LS243D?
The SN74LS243D is characterized for operation from 0°C to 70°C, matching commercial-grade TTL system requirements. This range aligns with standard industrial ambient conditions and excludes extended military or automotive extremes. The SN54LS243 variant supports –55°C to 125°C, but SN74LS243D strictly adheres to the 0°C–70°C specification per its datasheet revision SDLS145A.
Does SN74LS243D support true bidirectional operation on each channel?
Yes, SN74LS243D provides true per-channel bidirectionality: each of the four A/B line pairs (A1/B1 through A4/B4) can transmit independently in either direction based on GAB and GBA logic states. When GAB = L and GBA = H, data flows A→B; when GAB = H and GBA = L, data flows B→A; isolation occurs when both are high.
Can SN74LS243D drive unterminated PCB traces?
SN74LS243D is rated to drive terminated lines down to 133 Ω, implying intentional use with controlled-impedance or series-terminated traces. Driving unterminated traces longer than ~5 cm risks ringing and timing violations due to reflected energy; proper termination (e.g., 133 Ω at receiver end) is required for reliable operation per datasheet specifications.
What is the meaning of "Latch A and B" in the SN74LS243D function table?
"Latch A and B" refers to the functional state where both GAB and GBA are high (H), causing the outputs of A1–A4 and B1–B4 to mirror each other (A = B). This is not a storage latch but a forced equilibrium mode used for bus initialization, diagnostics, or synchronization-no clock or edge-triggering is involved.
Is SN74LS243D pin-compatible with SN74LS245N?
No, SN74LS243D is not pin-compatible with SN74LS245N. SN74LS243D uses a 14-pin SOIC layout with dedicated GAB (pin 1) and GBA (pin 11) controls, while SN74LS245N places DIR on pin 1 and OE on pin 19 (in 20-pin packages) or pin 1 (in 16-pin variants). Pin counts, assignments, and control signal topology differ fundamentally.
SN74LS243D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 4
- Input Type:
- -
- Output Type:
- Push-Pull
- Current - Output High, Low:
- 15mA, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
SN74LS243D FAQ
1.How can I place an order for SN74LS243D through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS243D 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 SN74LS243D reliable?
The price and inventory of SN74LS243D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS243D is usually 5 days.
3.What payment methods are accepted for SN74LS243D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS243D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS243D?
SN74LS243D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS243D 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 SN74LS243D?
For technical support, including SN74LS243D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS243D requirements.
6.How does Aetrix verify that SN74LS243D is sourced from the original manufacturer or authorized distributors?
All SN74LS243D 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 SN74LS243D meets industry standards.
7.What is the process for return or replacement of SN74LS243D?
All SN74LS243D units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS243D, 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 SN74LS243D part is unused and in its original packaging.
Return procedure for SN74LS243D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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