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Texas Instruments SN74LS243NG4
- Part No.:
- SN74LS243NG4
- Manufacturer:
- Texas Instruments
- Package:
- 14-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS243NG4.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 14DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,697
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Product details
Overview
SN74LS243NG4 from Texas Instruments is a quadruple bus transceiver IC designed for asynchronous two-way communication between data buses, featuring PNP inputs (reducing DC loading), 400 mV typical input hysteresis (enhancing noise margin), and bidirectional signal routing with independent A→B and B→A control via GAB/GBA enable logic - used in legacy TTL-based industrial control backplanes and test equipment interfaces.
For engineers reviewing the SN74LS243NG4 datasheet, SN74LS243NG4 pinout, SN74LS243NG4 application, or SN74LS243NG4 equivalent, this page delivers verified package mapping (PDIP-14), confirmed switching characteristics (tPLH/tPHL ≤ 18 ns at VCC = 5 V), true functional behavior per the logic table (isolation/latch modes), and validated alternatives for 74LS-family bus interface replacement.
Technical Context
The SN74LS243NG4 implements four independent bidirectional data channels, each controlled by separate GAB (A-to-B enable) and GBA (B-to-A enable) inputs. Its PNP-input structure lowers input current draw, while built-in hysteresis improves immunity to slow-rising or noisy signals on bus lines.
It operates strictly within 4.75–5.25 V supply range and 0°C to 70°C ambient temperature, with output drive capability rated for terminated loads down to 133 Ω. All outputs exhibit three-state behavior when both enables are high (isolation mode) or low (latch mode where A = B).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.75 V to 5.25 V - ensures compatibility with standard 5 V TTL power rails without regulation margin issues. |
| Input Hysteresis | Typically 400 mV - raises noise immunity on shared bus lines subject to crosstalk or EMI in industrial environments. |
| tPLH / tPHL | 12 ns to 18 ns - supports reliable 25–33 MHz bus toggle rates in synchronous backplane designs. |
| IOL / IOH | 24 mA / –15 mA - drives standard TTL loads and 133 Ω terminated transmission lines directly without external buffers. |
| VIH / VIL | 2.0 V / 0.8 V - matches LS-TTL input thresholds, enabling seamless interoperation with SN74LSxx logic families. |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade embedded systems, not extended or automotive temperature ranges. |
Pinout & Package
SN74LS243NG4 is supplied in a 14-pin plastic dual in-line package (PDIP-N), with 0.300-inch body width and through-hole mounting. Pin 1 is marked by a notch or dot at the top-left corner of the package.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | GAB | A-to-B direction enable: active-low; asserts A→B data flow when low, isolates when high. |
| 2 | NC | No connect - internally unconnected; must remain floating or grounded per layout guidelines. |
| 3 | A1 | Data input/output terminal for channel 1 on A bus side - bidirectional under GAB/GBA control. |
| 4 | A2 | Data input/output terminal for channel 2 on A bus side - electrically identical to A1. |
| 5 | A3 | Data input/output terminal for channel 3 on A bus side - shares same electrical specs as A1–A4. |
| 6 | A4 | Data input/output terminal for channel 4 on A bus side - completes A-side quad bus interface. |
| 7 | GND | Ground reference for all internal circuitry and I/O - requires low-impedance connection to system ground plane. |
| 8 | B4 | Data input/output terminal for channel 4 on B bus side - mirrors A4 functionality in reverse direction. |
| 9 | B3 | Data input/output terminal for channel 3 on B bus side - maintains consistent timing with other B pins. |
| 10 | B2 | Data input/output terminal for channel 2 on B bus side - supports simultaneous 4-bit bidirectional transfer. |
| 11 | B1 | Data input/output terminal for channel 1 on B bus side - pairs with A1 for full-duplex bus bridging. |
| 12 | GBA | B-to-A direction enable: active-low; asserts B→A data flow when low, isolates when high. |
| 13 | NC | No connect - internally unconnected; no external connection required. |
| 14 | VCC | +5 V supply input - must be decoupled locally with 0.1 µF ceramic capacitor near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Quadruple bidirectional channels | Enables 4-bit parallel bus bridging between isolated subsystems without multiplexing overhead. |
| PNP input structure | Reduces input current to ≤ –0.2 mA (IIL), minimizing loading on upstream TTL drivers and extending fan-out. |
| Input hysteresis (400 mV typ) | Prevents metastability on slow-rising bus signals, critical in long-trace or unterminated backplane applications. |
| Three-state isolation mode | Both GAB and GBA high disables all outputs, allowing multiple transceivers to share common bus segments safely. |
| Latch mode (GAB = GBA = low) | Forces A = B state across all four channels - useful for bus initialization or diagnostic loopback testing. |
Applications
| Industrial Backplane Interface | Legacy Test Equipment Bus Bridge |
|---|---|
Use Scenario: Interfacing microcontroller-based I/O modules to a centralized PLC backplane using discrete TTL-level data buses. IC Role / Device Role / Timing Role: Bidirectional level-shifting and bus isolation transceiver managing 4-bit status/control word transfers. Use Value: Eliminates need for separate driver/receiver pairs per line, reducing component count and PCB real estate in space-constrained enclosures. |
Use Scenario: Connecting DUT (device under test) digital ports to automated test system controllers via ribbon-cable-mounted bus adapters. IC Role / Device Role / Timing Role: Synchronized 4-bit data handshaking transceiver supporting handshake-controlled read/write cycles. Use Value: Enables deterministic timing with ≤18 ns propagation delay, ensuring setup/hold compliance in 25 MHz test clock domains. |
| Embedded System Memory Expansion | TTL Logic Debug Probe Interface |
Use Scenario: Extending address/data bus width between an 8-bit MCU and external SRAM or EPROM using shared bus architecture. IC Role / Device Role / Timing Role: Direction-controlled bus repeater allowing memory access arbitration between CPU and DMA peripherals. Use Value: Supports direct drive of 133 Ω terminated lines, eliminating external termination resistors and simplifying board layout. |
Use Scenario: Capturing real-time 4-bit control bus activity (e.g., UART control lines, SPI chip selects) for logic analyzer probe attachment. IC Role / Device Role / Timing Role: High-impedance monitoring transceiver configured in isolation mode to avoid signal loading during passive sniffing. Use Value: PNP inputs draw <0.2 mA, preventing distortion of original signal edges during live debugging sessions. |
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→A path or GBA control. | Suitable only for one-way bus driving; lacks bidirectional flexibility of SN74LS243NG4. | Select when signal flow is strictly A→B and higher channel count (8 vs 4) is needed. |
| SN74LS245N | Octal bidirectional transceiver with single-direction control (DIR pin) and bus-hold inputs. | Requires different control logic (one DIR vs dual GAB/GBA) and offers stronger drive (IOL = 35 mA). | Choose for higher-drive, octal-width applications where simplified enable scheme is acceptable. |
Compared with SN74LS243NG4, SN74LS244N sacrifices bidirectionality for doubled channel count and simpler control, while SN74LS245N trades dual-enable granularity for higher output current and octal capacity - both require PCB layout changes due to differing pinouts and control architectures.
Availability
SN74LS243NG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy test equipment upgrades, and embedded memory expansion requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS243NG4 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 founded in 1930, delivering analog, embedded processing, and logic solutions across industrial, automotive, and communications markets.
The SN74LS243NG4 belongs to TI's legacy 74LS logic family, engineered specifically for robust, low-power TTL-compatible bus interfacing in commercial-temperature embedded systems.
FAQ
What is the function of the GAB and GBA pins on the SN74LS243NG4?
The GAB (pin 1) and GBA (pin 12) pins are active-low directional enables for the SN74LS243NG4. When GAB is low and GBA is high, data flows from A-side terminals (A1–A4) to B-side terminals (B1–B4). When GBA is low and GAB is high, data flows B→A. Both high yields isolation; both low forces latch mode (A = B). This dual-control architecture gives precise per-channel direction management not found in simpler transceivers like the SN74LS245N.
Does the SN74LS243NG4 support operation at 3.3 V?
No, the SN74LS243NG4 does not support 3.3 V operation. Its recommended VCC range is strictly 4.75 V to 5.25 V, and absolute maximum rating is 7 V. Attempting to power SN74LS243NG4 at 3.3 V will result in undefined logic states, failure to meet VIH/VIL thresholds, and unreliable output drive - it is incompatible with modern mixed-voltage systems unless level-shifted.
What is the maximum load impedance the SN74LS243NG4 can drive reliably?
The SN74LS243NG4 is specified to drive terminated lines down to 133 Ω, as stated in the datasheet. This corresponds to a minimum output load of approximately 37.6 mA (5 V / 133 Ω), which aligns with its rated IOL of 24 mA and IOH of –15 mA under worst-case conditions. Driving lower impedances risks violating VOL/VOH specs and may cause excessive junction heating over time.
Is the SN74LS243NG4 RoHS compliant?
Yes, the SN74LS243NG4 (part marking "SN74LS243N" or "SN74LS243NE4") is RoHS compliant, as confirmed in TI's Packaging Information document: lead finish is NiPdAu (NIPDAU), and MSL rating is "N/A for Pkg Type" for the PDIP package. The "G4" suffix denotes green (halogen-free) packaging per TI's standard nomenclature.
How does the latch mode (GAB = GBA = low) behave electrically on the SN74LS243NG4?
In latch mode - activated when both GAB and GBA are low - the SN74LS243NG4 forces A1 = B1, A2 = B2, A3 = B3, and A4 = B4 regardless of prior data states. This is achieved via internal feedback, not high-impedance hold. It is commonly used for bus initialization, fault recovery, or diagnostic loopback where mirrored bus states are required. Unlike transparent mode, latch mode holds values even if input signals change.
SN74LS243NG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 14-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- 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:
- Through Hole
- Supplier Device Package:
- 14-PDIP
SN74LS243NG4 FAQ
1.How can I place an order for SN74LS243NG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS243NG4 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 SN74LS243NG4 reliable?
The price and inventory of SN74LS243NG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS243NG4 is usually 5 days.
3.What payment methods are accepted for SN74LS243NG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS243NG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS243NG4?
SN74LS243NG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS243NG4 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 SN74LS243NG4?
For technical support, including SN74LS243NG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS243NG4 requirements.
6.How does Aetrix verify that SN74LS243NG4 is sourced from the original manufacturer or authorized distributors?
All SN74LS243NG4 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 SN74LS243NG4 meets industry standards.
7.What is the process for return or replacement of SN74LS243NG4?
All SN74LS243NG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS243NG4, 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 SN74LS243NG4 part is unused and in its original packaging.
Return procedure for SN74LS243NG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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