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Texas Instruments SN74LS126ADR
- Part No.:
- SN74LS126ADR
- Manufacturer:
- Texas Instruments
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS126ADR.pdf
- Description:
- IC BUF NON-INVERT 5.25V 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,470
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Product details
Overview
SN74LS126ADR from Texas Instruments is a quad bus buffer with 3-state outputs, designed for bidirectional data bus isolation and load driving in TTL-compatible digital systems. It features independent active-low output enable (G) per channel, 24 mA low-level output drive, 2.6 mA high-level output sink capability, and operates at 5 V over 0°C to 70°C. It enables clean bus sharing in legacy industrial control and instrumentation backplanes.
For engineers reviewing the SN74LS126ADR datasheet, SN74LS126ADR pinout, SN74LS126ADR application, or SN74LS126ADR equivalent, key selection criteria include its active-low enable logic, SOIC-14 package compatibility, 15 ns typical propagation delay, and verified 3-state leakage of ±20 µA - critical for low-power bus hold integrity and multi-drop signal routing.
Technical Context
The SN74LS126ADR implements four independent non-inverting buffers, each with a dedicated active-low output enable input (G). When G is low, the output Y follows input A; when G is high, Y enters high-impedance state. Its LS-TTL circuitry uses bipolar transistor design optimized for speed-power trade-off over standard TTL.
It supports direct interfacing with 74LS, 74S, and 74F families without level-shifting. Input thresholds are VIH = 2.0 V (min), VIL = 0.8 V (max); output VOH = 2.4 V (min) at IOH = –2.6 mA, VOL = 0.4 V (max) at IOL = 24 mA - ensuring robust noise margin in mixed-logic environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS (Low-Power Schottky TTL) - delivers 1/10th the power of standard TTL with comparable speed. |
| Output Type | 3-State (active-low enable) - allows multiple devices to share a common bus without contention. |
| Propagation Delay | 15 ns typical (tPLH/tPHL @ VCC = 5 V, CL = 45 pF) - suitable for ≤33 MHz bus operation in legacy systems. |
| Output Drive | 24 mA sink / 2.6 mA source - drives heavy capacitive loads (e.g., >10 TTL inputs) without external pull-ups. |
| Supply Voltage | 4.75 V to 5.25 V - tight regulation required; not tolerant of 3.3 V or wide-range supplies. |
| Operating Temp | 0°C to 70°C - commercial-grade rating; not qualified for extended temperature or automotive use. |
| Input Leakage | ±0.4 mA max (IIL/IIH) - ensures stable logic levels even with high-impedance source termination. |
Pinout & Package
SN74LS126ADR is housed in a 14-pin SOIC (Small Outline Integrated Circuit) package, 3.90 mm wide, 8.65 mm long, 1.75 mm max height, RoHS-compliant with NiPdAu lead finish and MSL Level-1 reflow profile.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 4, 10, 13 | Output Enable (G) | Active-low control per channel; high = high-Z, low = enabled buffer pass-through. |
| 2, 5, 9, 12 | Data Input (A) | Non-inverting input; accepts standard TTL logic levels (0.8 V / 2.0 V thresholds). |
| 3, 6, 8, 11 | Buffered Output (Y) | 3-state totem-pole output; sinks 24 mA or sources 2.6 mA while maintaining VOH/VOL specs. |
| 7 | GND | Ground reference for all internal circuitry and output stage return path. |
| 14 | VCC | +5 V supply; decoupling capacitor (0.1 µF ceramic) required within 10 mm of pin. |
Key Features
| Feature | Design Value |
|---|---|
| Independent per-channel enable | Four separate G inputs allow selective activation of individual bus lines - essential for partial bus arbitration. |
| High-impedance off-state | IOZ ≤ ±20 µA ensures negligible loading on shared bus when disabled - prevents signal corruption during hot-swap or fault conditions. |
| LS-TTL compatibility | Matches voltage thresholds and drive strength of 74LS family - eliminates need for interface logic in legacy designs. |
| Robust short-circuit protection | IOS = –225 mA (max) with single-output short duration ≤1 s - protects against transient bus faults without latch-up. |
| SOIC tape-and-reel packaging | 2500-unit reels with Q1 pin-1 quadrant orientation - optimized for automated SMT placement and traceable lot control. |
Applications
| Industrial Backplane Bus Isolation | Legacy Test Equipment Data Routing |
|---|---|
Use Scenario: Isolating microcontroller address/data buses from peripheral modules in modular PLC racks. IC Role / Device Role / Timing Role: Quad buffer provides channelized enable control to prevent bus contention during module insertion/removal. Use Value: Enables hot-plug capability with <1 µA leakage in disable state, preserving bus integrity across 12+ slots. | Use Scenario: Routing parallel digital signals between pattern generator, DUT interface, and measurement capture logic in ATE systems. IC Role / Device Role / Timing Role: Acts as bidirectional repeater with sub-20 ns delay to maintain timing alignment across long PCB traces. Use Value: Delivers 24 mA drive to overcome 50–100 pF trace capacitance, eliminating signal rounding at 10 MHz test clock rates. |
| Embedded Instrumentation Signal Multiplexing | TTL-Level Serial Interface Buffering |
Use Scenario: Sharing a single 8-bit ADC data bus among multiple sensor front-ends in medical monitoring hardware. IC Role / Device Role / Timing Role: Buffers sensor data streams with independent G controls synchronized to multiplexer select lines. Use Value: Prevents cross-talk via 3-state isolation; maintains DC accuracy with <0.5 V VOL at full 24 mA load. | Use Scenario: Level-shifting and buffering RS-232 or UART control signals between microcontroller and legacy peripherals. IC Role / Device Role / Timing Role: Provides TTL-compatible drive for RTS/CTS/DTR lines where microcontroller GPIO lacks sufficient current. Use Value: Eliminates need for discrete transistors; supports 2.6 mA sourcing to drive opto-isolator LEDs directly. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS125ADR | Active-high output enable (G) vs. SN74LS126ADR's active-low G - inverted control logic. | Requires inverted enable signal generation; unsuitable where existing firmware assumes low-enable polarity. | Select SN74LS125ADR only if system control logic natively asserts enable high; verify timing impact of inverted setup/hold. |
| SN74HC126DR | CMOS-based (74HC), 2 V–6 V supply, higher input impedance, lower ICC (8 µA typ), but weaker drive (7.8 mA sink). | Not TTL-compatible; requires level translation when interfacing with 74LS/74S logic; better for low-power battery systems. | Choose SN74HC126DR only for new designs targeting wider VCC range and lower static power; avoid in mixed-logic backplanes without verification. |
Compared with SN74LS125ADR and SN74HC126DR, SN74LS126ADR uniquely satisfies legacy 5 V TTL bus systems requiring active-low enable, 24 mA drive, and guaranteed 15 ns timing - making it irreplaceable in field-replaceable industrial modules where control signal polarity and drive strength are fixed by installed base.
Availability
SN74LS126ADR is available at Aetrix Electronics and suitable for industrial backplane isolation, legacy test equipment signal routing, and embedded instrumentation data multiplexing requiring stable component supply across long-lifecycle programs.
Supply support for SN74LS126ADR 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 specializing in analog, embedded processing, and logic ICs, with decades of heritage in TTL and LS-TTL product lines.
The SN74LS126ADR belongs to TI's 74LS logic family, engineered specifically for reliable, low-power, high-drive digital interfacing in industrial, instrumentation, and military-grade systems operating at 5 V.
FAQ
What is the function of the G input on SN74LS126ADR?
The G input on SN74LS126ADR is an active-low output enable control for each of the four buffer channels. When G is low (≤0.8 V), the corresponding Y output follows the A input; when G is high (≥2.0 V), Y enters high-impedance state. This per-channel control enables selective bus line activation - a core feature used in SN74LS126ADR for dynamic bus arbitration in industrial backplanes.
Can SN74LS126ADR operate at 3.3 V?
No, SN74LS126ADR is not rated for 3.3 V operation. Its recommended VCC range is 4.75 V to 5.25 V, and absolute maximum VCC is 7 V. At 3.3 V, SN74LS126ADR fails to meet VIH/VIL thresholds, resulting in undefined logic states and unreliable 3-state control. Use SN74HC126DR instead for true 3.3 V–6 V compatibility.
What is the maximum capacitive load SN74LS126ADR can drive reliably?
SN74LS126ADR is characterized for CL = 45 pF in switching tests, with tPLH/tPHL specified up to that load. In practice, it reliably drives up to 100 pF while maintaining VOL ≤ 0.4 V at 24 mA sink, provided trace inductance is minimized and local VCC decoupling is used. Exceeding 100 pF risks timing skew and edge degradation - confirmed by SN74LS126ADR's 15 ns typical delay spec at 45 pF.
Is SN74LS126ADR pin-compatible with SN74LS125ADR?
Yes, SN74LS126ADR and SN74LS125ADR share identical SOIC-14 pinout and package dimensions. However, their enable logic is inverted: SN74LS126ADR uses active-low G, while SN74LS125ADR uses active-high G. Swapping them requires corresponding inversion of enable signals in firmware or hardware - SN74LS126ADR cannot be substituted without logic revision.
Does SN74LS126ADR support hot-swap insertion on a live bus?
SN74LS126ADR supports controlled hot-swap when powered before bus connection and enabled only after stabilization. Its 3-state outputs exhibit ≤20 µA off-state leakage (IOZ), minimizing disturbance to live buses. However, TI does not guarantee hot-swap robustness beyond standard ESD ratings (±2 kV HBM); external series resistors or bus guards are recommended for frequent insertion cycles - a design consideration validated in SN74LS126ADR's industrial backplane applications.
SN74LS126ADR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Logic Type:
- Buffer, Non-Inverting
- Number of Elements:
- 4
- Number of Bits per Element:
- 1
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 2.6mA, 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
SN74LS126ADR FAQ
1.How can I place an order for SN74LS126ADR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS126ADR 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 SN74LS126ADR reliable?
The price and inventory of SN74LS126ADR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS126ADR is usually 5 days.
3.What payment methods are accepted for SN74LS126ADR?
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4.How is shipping managed for SN74LS126ADR?
SN74LS126ADR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS126ADR 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 SN74LS126ADR?
For technical support, including SN74LS126ADR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS126ADR requirements.
6.How does Aetrix verify that SN74LS126ADR is sourced from the original manufacturer or authorized distributors?
All SN74LS126ADR 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 SN74LS126ADR meets industry standards.
7.What is the process for return or replacement of SN74LS126ADR?
All SN74LS126ADR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS126ADR, 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 SN74LS126ADR part is unused and in its original packaging.
Return procedure for SN74LS126ADR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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