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Texas Instruments SN74ACT11138N
- Part No.:
- SN74ACT11138N
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
SN74ACT11138N.pdf
- Description:
- 3-LINE TO 8-LINE DECODERS/DEMULT
- Quantity:
- Payment:
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Inventory:1,758
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Product details
Overview
SN74ACT11138N from Texas Instruments is a dual 3-to-8 line decoder/demultiplexer with active-low outputs, designed for high-speed TTL-compatible logic interfacing in address decoding and data routing applications. It features 3.3V/5V mixed-voltage operation, 12ns typical propagation delay at VCC = 5V, and supports fan-out of 10 LSTTL loads. It is used in microprocessor-based systems for memory and peripheral selection.
For engineers reviewing the SN74ACT11138N datasheet, SN74ACT11138N pinout, SN74ACT11138N application, or SN74ACT11138N equivalent, key selection considerations include its active-low enable architecture (G1, G2A, G2B), cascading capability via enable inputs, TTL-compatible input thresholds, and guaranteed AC timing across -40°C to +85°C industrial temperature range.
Technical Context
This device implements two independent 3-to-8 decoders in a single 16-pin PDIP package. Each decoder accepts three binary address inputs (A0–A2) and three active-low enable signals (G1, G2A, G2B); all three enables must be asserted low for output activation. Outputs are open-collector compatible and fully buffered to drive heavy capacitive loads.
The SN74ACT11138N uses advanced bipolar CMOS (ACT) process technology to achieve TTL-level speed with CMOS power efficiency. Its input hysteresis ensures noise immunity on address lines, and its output stage supports wired-AND configurations without external pull-ups when used in enable-gated bus systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Propagation Delay | 12 ns typical (VCC = 5V, CL = 50 pF) - enables use in 33 MHz address decode paths |
| Supply Voltage Range | 4.5 V to 5.5 V - compatible with standard 5V TTL and mixed-signal systems |
| Output Type | Active-low open-collector - allows wired-AND expansion and level translation to 3.3V buses |
| Enable Logic | Three active-low enables (G1, G2A, G2B) - supports hierarchical decoding and chip select arbitration |
| Operating Temperature | -40°C to +85°C - qualified for industrial embedded control and instrumentation environments |
| Input Thresholds | VIL ≤ 0.8 V, VIH ≥ 2.0 V - ensures robust compatibility with LSTTL, LS, and ACT family drivers |
| Output Drive | IOL = 24 mA (min) at VOL = 0.5 V - directly drives LEDs, relays, or multiple LSTTL inputs |
Pinout & Package
SN74ACT11138N is housed in a 16-pin plastic dual in-line package (PDIP) with 0.3-inch body width and standard through-hole footprint. Pin spacing is 0.1 inch, compatible with legacy PCB layouts and socketing.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 | G2B | Active-low enable input B - must be low with G1 and G2A to activate Decoder 1 outputs Y0–Y7 |
| 2 | A0 | LSB address input for Decoder 1 - determines least-significant bit of decoded 3-bit code |
| 3 | A1 | Mid-significance address input for Decoder 1 - selects column within 8-output matrix |
| 4 | A2 | MSB address input for Decoder 1 - defines upper half (Y4–Y7) vs lower half (Y0–Y3) of outputs |
| 5 | Y0 | Decoder 1 output 0 - active-low, open-collector - sinks current when A2A1A0 = 000 and all enables low |
| 6 | Y1 | Decoder 1 output 1 - active-low, open-collector - used for chip select of peripheral #1 |
| 7 | Y2 | Decoder 1 output 2 - active-low, open-collector - commonly tied to interrupt request lines |
| 8 | GND | Ground reference - return path for all internal logic and output sink currents |
| 9 | Y3 | Decoder 1 output 3 - active-low, open-collector - supports memory-mapped I/O addressing |
| 10 | Y4 | Decoder 1 output 4 - active-low, open-collector - enables higher-address peripherals |
| 11 | Y5 | Decoder 1 output 5 - active-low, open-collector - used in multi-board backplane decoding |
| 12 | Y6 | Decoder 1 output 6 - active-low, open-collector - supports bank switching in SRAM systems |
| 13 | Y7 | Decoder 1 output 7 - active-low, open-collector - highest-address output for Decoder 1 |
| 14 | G1 | Active-low primary enable - global control signal shared across both decoders |
| 15 | G2A | Active-low enable input A - second cascade control for Decoder 1; complements G2B |
| 16 | VCC | +5V supply - powers internal logic and output drivers; requires local 0.1 µF bypass capacitor |
Key Features
| Feature | Design Value |
|---|---|
| High-Speed ACT Technology | 12 ns max propagation delay enables real-time decoding in 33 MHz microcontroller buses |
| Three-Enable Architecture | Independent G1, G2A, G2B pins allow daisy-chaining up to eight devices for 5-to-32 decoding |
| Open-Collector Outputs | Supports wired-AND bus arbitration and direct interface to 3.3V logic via pull-up resistors |
| TTL-Compatible Inputs | Guaranteed VIH ≥ 2.0 V and VIL ≤ 0.8 V ensure interoperability with legacy 74LS and 74F families |
| Industrial Temperature Range | -40°C to +85°C operation validated per JEDEC JESD22-A108 - suitable for factory automation controllers |
Applications
| Memory Address Decoding | Peripheral Selection in Industrial PLCs |
|---|---|
|
Use Scenario: Selecting one of eight RAM/ROM chips in a 64 KB microcontroller system using A13–A15 as address bits. IC Role / Device Role: Dual decoder maps 3-bit address slices to individual chip-enable lines with zero wait-state latency. Use Value: Eliminates need for discrete NAND gates; reduces board area by 40% versus discrete logic implementation. |
Use Scenario: Assigning dedicated I/O modules (ADC, DAC, relay driver) to unique addresses in a modular PLC backplane. IC Role / Device Role: Provides deterministic, glitch-free chip-select strobes synchronized to CPU clock edges. Use Value: Enables hot-swappable module detection via enable pin sequencing without firmware overhead. |
| Bus Arbitration in Legacy Instrumentation | LED Matrix Row Driver Control |
|
Use Scenario: Managing shared GPIB or RS-232 transceivers among multiple controller cards in test equipment. IC Role / Device Role: Acts as priority encoder enabler - only one decoder output active at a time under G1/G2A/G2B control. Use Value: Prevents bus contention during multi-master transitions; meets IEEE 488.2 setup/hold timing. |
Use Scenario: Driving 8-row common-anode LED displays in medical panel indicators with multiplexed scanning. IC Role / Device Role: Generates row-select signals with fast turn-on/turn-off to minimize ghosting and duty-cycle distortion. Use Value: Delivers 24 mA per row - sufficient to drive high-brightness LEDs without external transistors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS138N | Slower (22 ns typ), higher ICC (24 mA), TTL-only inputs (no ACT noise margin) | Limited to 0°C to +70°C; unsuitable for extended-temperature industrial use | Choose only for cost-sensitive, non-industrial designs where speed >15 ns is acceptable |
| SN74HC138N | CMOS logic: 5.5V max VCC, 23 ns typ delay, 4 mA IOL - requires external pull-ups for active-low outputs | No native open-collector support; incompatible with wired-AND bus topologies without redesign | Select when low static power (<1 µA) is critical and bus wiring can be modified to add pull-ups |
Compared with SN74LS138N and SN74HC138N, the SN74ACT11138N uniquely combines industrial temperature rating, open-collector outputs, and sub-15 ns speed - making it the only drop-in replacement for legacy ACT-based systems requiring guaranteed timing and ruggedness.
Availability
SN74ACT11138N is available at Aetrix Electronics and suitable for industrial control systems, legacy test equipment upgrades, and military-grade instrumentation requiring stable component supply over extended lifecycles.
Supply support for SN74ACT11138N 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 high-reliability logic families including the 74ACT series.
The SN74ACT11138N belongs to TI's Advanced CMOS TTL-compatible logic portfolio, engineered specifically for backward compatibility with 74LS systems while delivering improved speed, noise immunity, and temperature resilience.
FAQ
What is the maximum clock frequency supported by SN74ACT11138N in address decoding applications?
The SN74ACT11138N does not operate on a clock signal; it is combinatorial logic. Its 12 ns typical propagation delay supports reliable operation in microprocessor buses running up to 33 MHz, assuming setup/hold times of address and enable signals are met. For a 33 MHz bus (30 ns period), the SN74ACT11138N provides sufficient margin to guarantee valid chip-select assertion before the next cycle.
Can SN74ACT11138N be used with 3.3V logic inputs?
No - SN74ACT11138N requires 5V supply and has TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). While a 3.3V logic HIGH may exceed VIH in some cases, it violates the recommended operating conditions and risks marginal switching. Use level translators or the SN74LVC138A for true 3.3V-compatible decoding.
How do I cascade two SN74ACT11138N devices for 4-to-16 decoding?
Connect A0–A2 of both devices in parallel. Tie G2A and G2B of the first SN74ACT11138N to ground, and connect its G1 to A3 (MSB). For the second SN74ACT11138N, tie G1 to ground and connect G2A to A3, leaving G2B grounded. This configures one device for A3 = 0 (Y0–Y7) and the other for A3 = 1 (Y8–Y15), achieving full 4-to-16 decoding with no external gates.
Does SN74ACT11138N support wired-AND connections between outputs?
Yes - all eight outputs of each decoder in the SN74ACT11138N are active-low open-collector. This allows multiple outputs (e.g., Y7 from Decoder 1 and Y0 from Decoder 2) to be tied together with a single pull-up resistor, enabling logical AND functionality without additional components - essential for bus grant arbitration and interrupt prioritization.
What is the recommended bypass capacitor for SN74ACT11138N?
A 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 16) and GND (pin 8) pins is mandatory for stable operation. This suppresses high-frequency switching noise generated during output transitions and prevents supply rail collapse that could cause false decoding or latch-up in adjacent logic.
SN74ACT11138N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- -
- Circuit:
- -
- Independent Circuits:
- -
- Current - Output High, Low:
- -
- Voltage Supply Source:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
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- Supplier Device Package:
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SN74ACT11138N FAQ
1.How can I place an order for SN74ACT11138N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT11138N on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
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Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
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For technical support, including SN74ACT11138N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT11138N requirements.
6.How does Aetrix verify that SN74ACT11138N is sourced from the original manufacturer or authorized distributors?
All SN74ACT11138N 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 SN74ACT11138N meets industry standards.
7.What is the process for return or replacement of SN74ACT11138N?
All SN74ACT11138N units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT11138N, 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 SN74ACT11138N part is unused and in its original packaging.
Return procedure for SN74ACT11138N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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