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Texas Instruments SN74LV138ATD
- Part No.:
- SN74LV138ATD
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LV138ATD.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74LV138ATD from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in SOIC-16 package, operating from 4.5 V to 5.5 V, with max propagation delay of 7.6 ns at 5 V, TTL-voltage-compatible inputs, and Ioff partial-power-down support. It enables high-speed memory decoding and data routing in industrial control logic and address demultiplexing circuits.
For engineers reviewing the SN74LV138ATD datasheet, SN74LV138ATD pinout, SN74LV138ATD application, or SN74LV138ATD equivalent, key selection criteria include enable-input logic configuration (G1 active-high, G2A/G2B active-low), output drive capability (±12 mA), latch-up immunity (>250 mA), and mixed-mode voltage operation across all ports.
Technical Context
The SN74LV138ATD implements positive-logic 3-to-8 decoding with three binary select inputs (A, B, C) and three enable inputs (G1, G2A, G2B), where only one of eight active-low outputs (Y0–Y7) is asserted per valid input combination. Its architecture supports cascading for larger decoders without external inverters - e.g., a 24-line decoder requires no additional gates.
It features Ioff circuitry that disables outputs during partial power-down, preventing backflow current when VCC = 0 V, and supports mixed-mode voltage operation: inputs tolerate TTL levels (VIH ≥ 2 V, VIL ≤ 0.8 V) while outputs swing rail-to-rail (VOH ≥ 3.8 V, VOL ≤ 0.55 V at 12 mA load) under 4.5–5.5 V supply.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5-V logic systems and tolerance against supply ripple. |
| tpd (Max) | 7.6 ns at VCC = 5 V, CL = 15 pF - enables use in high-speed address decoding where system timing budgets are tight. |
| Ioff Support | Active at VCC = 0 V - allows safe insertion/removal in hot-swap or multi-rail systems without damaging back-current. |
| Output Drive | ±12 mA - sufficient to directly drive multiple CMOS/TTL inputs or small LED indicators without buffering. |
| Input Compatibility | TTL-voltage compatible (VIH ≥ 2 V, VIL ≤ 0.8 V) - interfaces seamlessly with legacy 5-V TTL logic families. |
| Latch-Up Immunity | >250 mA per JESD 17 - meets industrial reliability requirements for robust operation in noisy environments. |
| Operating Temp | –40°C to +125°C - qualified for extended temperature applications including automotive under-hood and industrial PLCs. |
Pinout & Package
SN74LV138ATD is housed in a 16-pin SOIC (D) package, 7.5 mm × 10.3 mm body size, 1.75 mm height, with 1.27 mm pitch and gull-wing leads. Pin 1 is located at the top-left corner marked by a beveled edge or dot.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (G2A) | Active-low enable input | Must be low to activate decoding; used with G2B and G1 to gate entire output array. |
| 2 (G2B) | Active-low enable input | Second active-low enable; both G2A and G2B must be low for device to respond to selects. |
| 3 (G1) | Active-high enable input | Must be high to enable function; provides flexible enable polarity for hierarchical decoding trees. |
| 4 (C) | Binary select input (MSB) | Most significant bit of 3-bit address; determines Y4–Y7 vs Y0–Y3 group activation. |
| 5 (B) | Binary select input | Mid-bit of address; combined with A and C to uniquely select one of eight outputs. |
| 6 (A) | Binary select input (LSB) | Least significant bit; final bit resolving output line within selected group. |
| 7 (Y0) | Active-low decoded output | Asserted low when A=B=C=0 and enables active; drives downstream logic or enable lines. |
| 8 (GND) | Ground reference | Primary return path for all internal logic and output currents; requires low-impedance PCB connection. |
| 9 (Y1) | Active-low decoded output | Asserted low for A=1, B=C=0; used in address decoding for peripheral chip-select generation. |
| 10 (Y2) | Active-low decoded output | Asserted low for B=1, A=C=0; supports memory bank selection in 8-bit microcontroller systems. |
| 11 (Y3) | Active-low decoded output | Asserted low for A=B=1, C=0; commonly tied to enable signal of UART or SPI peripheral ICs. |
| 12 (Y4) | Active-low decoded output | Asserted low for C=1, A=B=0; routes control signals to higher-address peripherals in bus architectures. |
| 13 (Y5) | Active-low decoded output | Asserted low for A=1, C=1, B=0; used in FPGA configuration logic or CPLD address expansion. |
| 14 (Y6) | Active-low decoded output | Asserted low for B=1, C=1, A=0; enables analog front-end channel selection in data acquisition modules. |
| 15 (Y7) | Active-low decoded output | Asserted low only when A=B=C=1; often reserved for system reset or diagnostic mode activation. |
| 16 (VCC) | Positive supply | 5-V nominal supply; bypass capacitor (0.1 µF ceramic) required within 5 mm of this pin for noise suppression. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs with mixed polarity | G1 (active-high) + G2A/G2B (active-low) reduce need for external inverters in multi-level decode trees. |
| Ioff partial-power-down protection | Disables outputs when VCC = 0 V, preventing backflow current in powered-down subsystems. |
| TTL-compatible input thresholds | VIH ≥ 2 V and VIL ≤ 0.8 V allow direct interface with legacy 5-V TTL without level-shifting. |
| Low ground bounce (VOLP < 0.8 V) | Minimizes noise coupling into shared ground planes in dense digital layouts. |
| High noise immunity (VOHV > 2.3 V) | Ensures reliable high-state recognition despite transient undershoot on output lines. |
| ESD robustness (HBM 2000 V) | Withstands handling and board assembly without special ESD precautions beyond standard practices. |
Applications
| Memory Address Decoding | Peripheral Chip-Select Generation |
|---|---|
|
Use Scenario: Selecting one of eight SRAM or Flash memory chips in a microcontroller-based embedded system with 16-bit address bus. IC Role / Device Role / Timing Role: SN74LV138ATD acts as a high-speed address decoder, using upper address bits (A13–A15) and chip-enable signals to assert individual /CE lines. Use Value: Propagation delay ≤7.6 ns ensures decoder latency adds negligible overhead to memory access time, preserving system throughput. |
Use Scenario: Assigning dedicated chip-select lines to UART, SPI, I²C, ADC, DAC, and GPIO expanders on an industrial controller PCB. IC Role / Device Role / Timing Role: SN74LV138ATD serves as a demultiplexer, converting 3-bit peripheral ID bus into eight independent active-low enable signals. Use Value: Mixed-polarity enables (G1, G2A, G2B) simplify integration with existing enable logic without adding discrete inverters. |
| FPGA Configuration Logic | Data Acquisition Channel Routing |
|
Use Scenario: Managing configuration modes and boot sources for Xilinx Spartan or Intel MAX 10 FPGAs requiring multiple JTAG or SPI flash options. IC Role / Device Role / Timing Role: SN74LV138ATD decodes mode pins to select between primary/secondary configuration devices or debug interfaces. Use Value: Ioff support allows safe reconfiguration while other FPGA power domains remain active, avoiding latch-up risk. |
Use Scenario: Routing analog sensor inputs to one of eight ADC channels in a modular test equipment platform with interchangeable front-end modules. IC Role / Device Role / Timing Role: SN74LV138ATD controls analog multiplexer enable lines based on digital control bus, synchronizing with sampling clock. Use Value: ±12 mA output drive directly switches high-capacitance analog mux control inputs without added buffer stages. |
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 |
|---|---|---|---|
| SN74HC138N | Higher propagation delay (21 ns typ at 6 V), narrower VCC range (2–6 V), no Ioff support. | Suitable for cost-sensitive consumer designs but not partial-power-down systems. | Choose SN74HC138N only if supply is stable 5 V and hot-swap safety is not required. |
| 74LVC138APW | Lower VCC range (1.65–3.6 V), 3.3-V optimized, 5.5-V tolerant inputs, no Ioff. | Designed for mixed-voltage 3.3-V systems interfacing to 5-V peripherals via level-tolerant inputs. | Select 74LVC138APW when main system runs at 3.3 V and must interface with 5-V legacy components. |
Compared with SN74HC138N and 74LVC138APW, the SN74LV138ATD uniquely combines 5-V speed (7.6 ns), industrial temperature range (–40°C to 125°C), and Ioff protection - making it the only choice for robust, hot-swap-capable 5-V decoding in demanding environments.
Availability
SN74LV138ATD is available at Aetrix Electronics and suitable for industrial PLCs, automotive body control modules, and medical diagnostic equipment requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SN74LV138ATD 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, specializing in analog, embedded processing, and connectivity technologies with broad industrial, automotive, and communications reach.
The SN74LV138ATD belongs to TI's LV logic family, engineered for high-speed 5-V operation with enhanced noise immunity and power-down safety - targeting industrial control, instrumentation, and legacy-system upgrades.
FAQ
What is the maximum propagation delay of the SN74LV138ATD at 5 V?
The SN74LV138ATD has a maximum propagation delay (tpd) of 7.6 ns at VCC = 5 V, CL = 15 pF, and TA = 25°C. This value increases to 10.4 ns at TA = –40°C to 85°C and up to 13 ns at TA = 125°C under same load conditions - critical for timing-critical address decoding paths.
Does the SN74LV138ATD support partial-power-down operation?
Yes, the SN74LV138ATD includes Ioff circuitry that disables all outputs when VCC = 0 V, preventing damaging current backflow from live buses into the unpowered device. This feature is explicitly verified in the datasheet under "Ioff Supports Partial-Power Down Mode Operation" and tested per JEDEC JESD78.
What are the enable-input logic polarities for the SN74LV138ATD?
The SN74LV138ATD uses three enable inputs: G1 is active-high, while G2A and G2B are both active-low. All three must be simultaneously asserted (G1 = H, G2A = L, G2B = L) for the decoder to respond to A/B/C inputs - enabling flexible hierarchical decoding without external inversion.
Can the SN74LV138ATD interface directly with TTL logic families?
Yes, the SN74LV138ATD features TTL-voltage-compatible inputs: VIH ≥ 2 V and VIL ≤ 0.8 V over 4.5–5.5 V supply, allowing direct connection to standard 74LS, 74F, and other 5-V TTL outputs without level shifters or pull-up resistors.
Is the SN74LV138ATD pin-compatible with other 74-series 3-to-8 decoders?
No - the SN74LV138ATD shares the same 16-pin SOIC footprint and functional pinout (per TI's D-package drawing DB0016A) with SN74HC138N and SN74HCT138N, but differs electrically in speed, drive strength, and Ioff support. Mechanical compatibility does not guarantee drop-in replacement without validation of timing and power-down behavior.
SN74LV138ATD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LV
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 12mA, 12mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74LV138ATD FAQ
1.How can I place an order for SN74LV138ATD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LV138ATD 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 SN74LV138ATD reliable?
The price and inventory of SN74LV138ATD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LV138ATD is usually 5 days.
3.What payment methods are accepted for SN74LV138ATD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LV138ATD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LV138ATD?
SN74LV138ATD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LV138ATD 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 SN74LV138ATD?
For technical support, including SN74LV138ATD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LV138ATD requirements.
6.How does Aetrix verify that SN74LV138ATD is sourced from the original manufacturer or authorized distributors?
All SN74LV138ATD 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 SN74LV138ATD meets industry standards.
7.What is the process for return or replacement of SN74LV138ATD?
All SN74LV138ATD units undergo pre-shipment inspection (PSI). If there is an issue with SN74LV138ATD, 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 SN74LV138ATD part is unused and in its original packaging.
Return procedure for SN74LV138ATD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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