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Texas Instruments SN74AHCT138MDREP
- Part No.:
- SN74AHCT138MDREP
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74AHCT138MDREP.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74AHCT138MDREP from Texas Instruments is a radiation-tolerant, high-speed 3-line to 8-line decoder/demultiplexer in SOIC-16 package, featuring TTL-compatible inputs, –55°C to 125°C extended temperature operation, 10.4 ns max propagation delay at 5 V/15 pF, and three enable inputs (G1 active-high, G2A/G2B active-low) for cascading. It is used in high-performance memory decoding and data-routing systems where minimal system delay is critical.
For engineers reviewing the SN74AHCT138MDREP datasheet, SN74AHCT138MDREP pinout, SN74AHCT138MDREP application, or SN74AHCT138MDREP equivalent, key selection criteria include its EPIC™ process qualification, latch-up immunity (>250 mA), ESD robustness (2000 V HBM), and compatibility with fast-enable memory subsystems requiring sub-12 ns timing margins.
Technical Context
This device implements positive-logic binary decoding with active-low outputs (Y0–Y7), where input combinations on A/B/C select exactly one asserted low output when all enables are satisfied. Its three independent enable inputs-G1 (high-active), G2A and G2B (both low-active)-enable hierarchical expansion without external inverters: two SN74AHCT138MDREP units implement a 24-line decoder, while three units plus one inverter yield 32-line decoding.
The SN74AHCT138MDREP uses TI's EPIC™ (Enhanced-Performance Implanted CMOS) process, ensuring stable operation across military-grade thermal extremes and meeting JEDEC JESD22-A110 (HAST), JESD22-A104 (temp cycle), and JESD22-A114 (autoclave) reliability standards. All inputs tolerate TTL voltage levels (VIH ≥ 2 V, VIL ≤ 0.8 V) while interfacing with 5-V CMOS logic rails.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures compatibility with standard 5-V logic systems and rejects supply noise up to ±0.5 V. |
| Propagation Delay | 7.6–10.4 ns (CL = 15 pF) - enables use in memory systems where decoder delay must be less than typical access time. |
| Output Drive | ±8 mA - supports direct fan-out to ≥10 LSTTL loads without buffering. |
| Input Compatibility | TTL-voltage level (VIH ≥ 2 V, VIL ≤ 0.8 V) - allows seamless interface with legacy TTL controllers and microcontrollers. |
| Operating Temperature | –55°C to 125°C - qualified per MIL-PRF-38535 for aerospace, defense, and downhole industrial applications. |
| ESD Rating | 2000 V HBM - eliminates need for external protection diodes in ruggedized PCB layouts. |
| Latch-Up Immunity | >250 mA per JESD17 - prevents destructive current runaway during transient overvoltage events. |
Pinout & Package
SN74AHCT138MDREP is housed in a 16-pin SOIC (D) package with 1.27 mm pitch, JEDEC MS-012AC compliant, and RoHS-compliant NiPdAu lead finish. Thermal resistance θJA is 73°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (G2A) | Enable input | Active-low enable; must be low with G2B low and G1 high to activate decoding function. |
| 2 (G2B) | Enable input | Second active-low enable; both G2A and G2B must be low for device to respond to selects. |
| 3 (G1) | Enable input | Active-high enable; all three enables required for output assertion. |
| 4 (C) | Select input | MSB of 3-bit binary address; determines high-order bit of decoded octal output line. |
| 5 (B) | Select input | Mid-bit of address; combined with A and C to uniquely select Y0–Y7. |
| 6 (A) | Select input | LSB of address; toggling A flips between adjacent output pairs (e.g., Y0/Y1). |
| 7 (Y0) | Output | Active-low decoded output corresponding to A=B=C=0; sinks current when selected. |
| 8 (GND) | Power | Ground reference for all internal circuitry and output drivers. |
| 9 (Y1) | Output | Active-low output for A=1, B=C=0; identical electrical specs to Y0–Y7. |
| 10 (Y2) | Output | Active-low output for A=0, B=1, C=0; shares drive strength and timing with all Yx outputs. |
| 11 (Y3) | Output | Active-low output for A=B=1, C=0; asserted only when enables and select match. |
| 12 (Y4) | Output | Active-low output for C=1, A=B=0; used in higher-address memory banks. |
| 13 (Y5) | Output | Active-low output for C=1, A=1, B=0; supports modular address decoding schemes. |
| 14 (Y6) | Output | Active-low output for C=1, A=0, B=1; enables 24-line expansion with second device. |
| 15 (Y7) | Output | Active-low output for A=B=C=1; final line in full 3-to-8 decode map. |
| 16 (VCC) | Power | +5 V supply rail; decoupling capacitor required within 10 mm for stable high-speed switching. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables hierarchical decoding: two devices cascade to 24-line without inverters; third + inverter yields 32-line. |
| EPIC™ process technology | Delivers extended temperature operation (–55°C to 125°C) with JEDEC-qualified reliability for mission-critical systems. |
| TTL-compatible inputs | Accepts standard TTL logic thresholds (VIH ≥ 2 V, VIL ≤ 0.8 V), eliminating level-shifter requirements in mixed-logic designs. |
| Low propagation delay | 7.6 ns typical tPLH/tPHL at 5 V/15 pF ensures decoder delay is negligible versus memory access times. |
| High noise immunity | Input hysteresis and 2000 V HBM ESD rating reduce susceptibility to radiated/transient coupling in noisy environments. |
Applications
| Memory Address Decoding | Data Demultiplexing |
|---|---|
Use Scenario: Selecting one of eight memory banks in a 64 kB SRAM subsystem using A15–A13 as C–A inputs. IC Role / Device Role / Timing Role: 3-to-8 address decoder asserting chip-select lines with sub-12 ns delay to avoid adding latency to read/write cycles. Use Value: Enables full utilization of fast SRAM access time (<25 ns) by keeping decode overhead below 10% of total cycle. | Use Scenario: Routing a single serial data stream from a UART to one of eight peripheral registers via G1 as data input. IC Role / Device Role / Timing Role: Active-low demultiplexer where G1 carries data and A/B/C select destination register. Use Value: Eliminates need for discrete logic gates or FPGA resources to implement 1:8 data routing in space-constrained avionics modules. |
| Modular I/O Expansion | High-Reliability Control Logic |
Use Scenario: Expanding GPIO count on a radiation-hardened microcontroller by enabling eight latched output ports. IC Role / Device Role / Timing Role: Decoder driving enable pins of octal latches (e.g., SN74AHCT573), synchronized to system clock edge. Use Value: Provides deterministic, glitch-free port selection with guaranteed setup/hold margins under temperature extremes. | Use Scenario: Implementing fault-tolerant watchdog reset distribution across eight subsystems in satellite power management. IC Role / Device Role / Timing Role: Decoded output triggers isolated reset circuits; G2A/G2B tied to health-monitor signals for conditional activation. Use Value: Ensures fail-safe reset sequencing even during single-point failures, leveraging triple-enable safety interlock. |
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 |
|---|---|---|---|
| SN74AHCT138MPWREP | TSSOP-16 package (4.4 mm width); θJA = 108°C/W; identical electrical specs and pinout. | Better PCB area efficiency but lower thermal performance; preferred for compact surface-mount layouts with adequate airflow. | Select SN74AHCT138MPWREP when board space is constrained and thermal derating is acceptable. |
| SN54AHCT138 | MIL-PRF-38535 QML-qualified; same SOIC-16 package; identical timing and DC specs; enhanced screening and traceability. | Required for DoD and NASA programs mandating Class V or Class H processing; includes lot-level radiation test reports. | Choose SN54AHCT138 when compliance with military procurement specifications (e.g., SMD 5962-03655) is mandatory. |
Compared with SN74AHCT138MPWREP, SN74AHCT138MDREP offers superior thermal dissipation in convection-cooled environments; compared with SN54AHCT138, it lacks QML documentation and radiation test records but meets identical electrical and environmental performance limits for commercial-space and industrial applications.
Availability
SN74AHCT138MDREP is available at Aetrix Electronics and suitable for aerospace avionics, downhole instrumentation, and defense electronics requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SN74AHCT138MDREP 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 high-reliability logic solutions for industrial, automotive, and aerospace markets.
The SN74AHCT138MDREP belongs to TI's enhanced-product (EP) logic family, engineered for extended temperature operation and diminished manufacturing source (DMS) continuity in mission-critical systems.
FAQ
What is the maximum operating temperature range for SN74AHCT138MDREP?
The SN74AHCT138MDREP is rated for continuous operation from –55°C to 125°C, qualified per JEDEC JESD22-A104 (temperature cycling) and JESD22-A110 (HAST), making it suitable for downhole, aerospace, and military platforms where ambient extremes are routine. This range is explicitly confirmed in the SCLS491 datasheet revision and TI's packaging addendum.
Does SN74AHCT138MDREP support TTL-level input signals?
Yes, SN74AHCT138MDREP features TTL-voltage compatible inputs: VIH is guaranteed ≥2.0 V and VIL ≤0.8 V over the full temperature range, allowing direct connection to legacy TTL outputs without level shifters. This is documented in the "Recommended Operating Conditions" table of the SCLS491 datasheet.
Can SN74AHCT138MDREP be used for demultiplexing applications?
Yes, SN74AHCT138MDREP supports demultiplexing by using G1 as the data input while holding G2A and G2B low and applying address bits to A/B/C. When G1 is high, no output activates; when G1 is low, the selected Yx output goes low - effectively routing one input to eight destinations. This mode is explicitly described in the device functional description and Figure 1 timing diagrams.
What is the propagation delay of SN74AHCT138MDREP at 5 V supply?
At VCC = 5 V and CL = 15 pF, SN74AHCT138MDREP exhibits tPLH and tPHL values of 7.6 ns (typical) to 10.4 ns (maximum) for A/B/C-to-Y transitions, and 6.6–10.5 ns for G1-to-Y transitions. These values are measured per JEDEC standards and published in the "Switching Characteristics" section of SCLS491.
Is SN74AHCT138MDREP pin-compatible with standard SN74AHCT138 variants?
Yes, SN74AHCT138MDREP shares identical pinout, electrical characteristics, and functional behavior with the commercial SN74AHCT138 and military SN54AHCT138, differing only in enhanced product qualifications (EPIC™ process, extended temp screening, DMS support). The SOIC-16 footprint and signal mapping are fully interchangeable per TI's packaging addendum.
SN74AHCT138MDREP Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 8mA, 8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74AHCT138MDREP FAQ
1.How can I place an order for SN74AHCT138MDREP through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHCT138MDREP 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 SN74AHCT138MDREP reliable?
The price and inventory of SN74AHCT138MDREP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHCT138MDREP is usually 5 days.
3.What payment methods are accepted for SN74AHCT138MDREP?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AHCT138MDREP transactions.
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4.How is shipping managed for SN74AHCT138MDREP?
SN74AHCT138MDREP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHCT138MDREP 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 SN74AHCT138MDREP?
For technical support, including SN74AHCT138MDREP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHCT138MDREP requirements.
6.How does Aetrix verify that SN74AHCT138MDREP is sourced from the original manufacturer or authorized distributors?
All SN74AHCT138MDREP 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 SN74AHCT138MDREP meets industry standards.
7.What is the process for return or replacement of SN74AHCT138MDREP?
All SN74AHCT138MDREP units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHCT138MDREP, 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 SN74AHCT138MDREP part is unused and in its original packaging.
Return procedure for SN74AHCT138MDREP:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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