SN75123D - Dual TTL Line Driver | Texas Instruments
MPN： SN75123D ✓ 啟用中SN75123D 概覽
A line driver is a digital interface IC that converts logic-level inputs into stronger output signals capable of driving terminated cables, coaxial links, or twisted-pair lines. The dual SN75123 belongs to the line-driver and receiver class of interface ICs. Its primary role is to improve signal integrity and drive capability across long or shared bus wiring rather than to perform data conversion or voltage regulation.
The SN75123D operates from one 5 V supply and is compatible with standard-TTL logic levels. Its emitter-follower outputs are designed for low-impedance line driving and support party-line operation, where multiple drivers can share a bus when their outputs are appropriately controlled. The output structure also provides short-circuit protection, a useful characteristic when a connected line is faulted or incorrectly terminated.
The 3.11 V output level at -59.3 mA indicates strong high-level output drive capability. With a maximum transmit delay of 25 ns, the device supports communication systems that require faster edge propagation than general-purpose logic buffers. The manufacturer identifies the SN75123 family as meeting or exceeding the IBM System 360 input/output interface requirements while remaining compatible with standard-TTL supply and logic levels.
Typical uses include terminated coaxial cable links, twisted-pair communication channels, computer peripheral interfaces, industrial data links, and legacy equipment built around TTL or IBM System 360 interfaces. Because the outputs use an uncommitted emitter-follower structure, designers can implement party-line networks in which connected drivers share the same physical conductor.
For a new design, verify the receiver's threshold requirements, line termination, cable length, and grounding arrangement before assigning the driver. The 16-pin SOIC package simplifies assembly and rework, but the output enable, input, ground, and supply pins must be connected according to the manufacturer datasheet. A single 5 V rail and common ground reference are fundamental to reliable operation.
This product page combines the manufacturer's functional description with engineering-focused comparison, application, and design guidance. It also clearly distinguishes directly substitutable components from candidates that require different packages or interfaces, helping engineers preserve PCB compatibility when planning replacements or design reuse.
直接替換替代品，適用於 SN75123D — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此產品無可直接替換的替代品。
申請替代品SN75123D 規格
| Product Type | Dual line driver |
| Number of Drivers | 2 channels |
| 供應電壓 | 5 V |
| Maximum Supply Voltage | 5.25 V |
| Logic Compatibility | Standard TTL |
| Interface Standard | IBM System 360 input/output interface |
| 輸出電壓 | 3.11 V at -59.3 mA |
| Maximum Transmit Delay | 25 ns |
| Maximum Supply Current | 60 mA |
| Output Structure | Uncommitted emitter-follower |
| Party-Line Operation | Supported |
| Short-Circuit Protection | Yes |
| 封裝 | 16-pin SOIC |
| 安裝類型 | Surface mount |
| Terminal Count | 16 terminals |
SN75123D 16-pin soic 腳位配置指南
SN75123D（16-pin soic 封裝）的腳位配置。 腳位編號、功能與連接圖定義於製造商資料手冊中。請參閱該手冊以取得確切的封裝尺寸與焊接指引。
無詳細腳位定義資料： SN75123D.
請參閱 資料表 以查看完整腳位配置。
典型應用
SN75123D 適用於 6 應用s: Terminated Coaxial Data Links, Twisted-Pair Communication Channels, IBM System 360 Legacy Interfaces, Party-Line Peripheral Buses, Industrial Data Acquisition, Test and Measurement Interfaces.
Terminated Coaxial Data Links
The SN75123D is appropriate for terminated coaxial data links because its dual emitter-follower outputs provide low-impedance drive for cable-connected receivers. The manufacturer specifies a 3.11 V output at -59.3 mA and a maximum transmit delay of 25 ns, allowing the device to retain useful signal strength and timing performance across a designed line. The transmitter operates from one 5 V supply and is compatible with standard-TTL inputs. In implementation, the cable characteristic impedance, receiver input loading, shield connection, and source termination should be evaluated together because the device does not create an appropriate termination by itself.
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Twisted-Pair Communication Channels
The SN75123D can drive twisted-pair communication channels where the system requires a single-ended TTL-compatible interface and stronger source drive than standard logic provides. Its low-impedance emitter-follower outputs are specifically described for terminated lines, while short-circuit protection helps contain fault conditions on an externally routed conductor. With a maximum transmit delay of 25 ns, the device is suitable for moderate-speed communication links. PCB implementation should provide a continuous return path, proper line termination, and clean separation between the two driver channels to limit crosstalk.
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IBM System 360 Legacy Interfaces
The SN75123D was designed specifically for IBM System 360 input/output interface requirements and is therefore relevant to equipment that retains this legacy electrical interface. It operates from a single 5 V supply, accepts standard-TTL-compatible signals, and provides two independent line-driver channels for terminated conductors. The 3.11 V output at -59.3 mA supports the stronger signaling expected by this interface class. When modernizing legacy equipment, preserve the original termination and receiver arrangement unless a complete signal-integrity review establishes that the interface can be adapted safely.
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Party-Line Peripheral Buses
The SN75123D fits party-line peripheral buses because its uncommitted emitter-follower outputs allow multiple connected drivers to share one conductor when their enables are sequenced correctly. This architecture suits legacy backplane and peripheral arrangements in which every attached transmitter can be placed in a high-impedance state. Short-circuit protection improves robustness when a connected line is faulted. Timing must still prevent two enabled drivers from driving the bus in opposite states, and the system designer should validate contention behavior, receiver thresholds, and cable fall time before production use.
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Industrial Data Acquisition
The SN75123D can serve as the line transmitter in industrial data-acquisition equipment that uses a legacy 5 V TTL-compatible cable interface. Its two channels reduce the component count for dual-line links, while the stated 25 ns maximum transmit delay supports communication at speeds substantially above slow asynchronous control rates. The emitter-follower output and short-circuit protection are useful in externally connected equipment. Industrial qualification still depends on the complete system's temperature requirements, surge protection, isolation strategy, and regulatory compliance rather than the line-driver IC alone.
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Test and Measurement Interfaces
The SN75123D is useful in test and measurement equipment that must stimulate remote receivers over terminated cable runs. Its low-impedance emitter-follower outputs provide stronger drive than conventional logic buffers, while the 3.11 V output at -59.3 mA specification supports a defined high-level load. The maximum transmit delay of 25 ns provides useful timing margin for moderate-speed control or measurement buses. Instrument designers should account for cable attenuation, connector reflections, receiver loading, and the difference between logical command speed and the rise time of the physical transmission line.
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推薦產品摘要
工程參考資料，適用於 SN75123D — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 |
|---|---|
| Product Type | Dual line driver |
| Number of Channels | 2 |
| Supply Voltage | 5 V |
| Maximum Supply Voltage | 5.25 V |
| Output Voltage | 3.11 V at -59.3 mA |
| Maximum Transmit Delay | 25 ns |
| Maximum Supply Current | 60 mA |
| Logic Compatibility | Standard TTL |
| Output Structure | Uncommitted emitter-follower |
| Package | 16-pin SOIC |
| Brand | Texas Instruments |
設計說明
Do not enable two SN75123D outputs simultaneously when they connect to the same party-line conductor with opposite output states. The uncommitted emitter-follower architecture permits shared-bus use only when output-enable sequencing keeps inactive drivers at high impedance. Review every connected driver and receiver in the complete bus, not just the local transmitter.
Treat the external line as a transmission-line problem when distance, data rate, or connector transitions are significant. Characteristic-impedance matching, source or load termination, stub length, and connector reflections determine whether the 3.11 V output at -59.3 mA and 25 ns maximum transmit delay produce a usable receiver waveform. Validate the assembled cable and termination network with suitable measurement equipment.
Route each driver output directly toward its connector or termination network, and keep the return-current path continuous beneath or adjacent to the signal trace. Place local supply bypassing at the device and maintain a low-impedance ground reference. Separate the two line-driver channels when they carry unrelated or high-slew-rate signals to minimize crosstalk.
Design the 5 V rail for the stated 60 mA maximum supply current plus the load presented by the receiving interface and associated circuitry. Decoupling should follow the manufacturer datasheet recommendations, and the supply must remain within the 5.25 V maximum. Verify startup and fault behavior at the board level rather than assuming the nominal 5 V rail is always sufficient.
合規資訊
No explicit compliance declarations are identified in the manufacturer product-page summary or distributor results. Confirm RoHS, REACH, lead-free, halogen-free, and conflict-minerals status from the current manufacturer documentation or applicable material declarations before procurement.